# MQTT Component

A lightweight, fully-featured MQTT client implementation.

## Syntax

```text
TiotMQTT
```

## Remarks

The MQTT component provides a lightweight, fully-featured MQTT client implementation with support for versions 3.1.1 and 5.0. The component supports plaintext and TLS-enabled connections over both standard TCP and WebSockets.

### Connecting

 Connecting to an MQTT server is easy; in the simplest case, set the [ClientId](#clientid-property-mqtt-component) property and call the [ConnectTo](#connectto-method-mqtt-component) method, passing it the server's hostname and port number.

When connecting to an MQTT server, the component sends the following information:

- The values of the [ClientId](#clientid-property-mqtt-component), [CleanSession](#cleansession-property-mqtt-component), and [KeepAliveInterval](#keepaliveinterval-property-mqtt-component) properties.
- The value of the [User](#user-property-mqtt-component) property (if non-empty).
- The value of the [Password](#password-property-mqtt-component) property (if non-empty).
- The values of the [WillTopic](#willtopic-property-mqtt-component) and [WillMessage](#willmessage-property-mqtt-component) properties and the [WillQOS](#WillQOS) and [WillRetain](#WillRetain) configuration settings.
- MQTT 5 specific values from [ClientTopicAliasMax](#ClientTopicAliasMax), [SessionExpInterval](#SessionExpInterval), [ConnectProperties](#ConnectProperties) and [WillProperties](#WillProperties).

If [CleanSession](#cleansession-property-mqtt-component) is *True*, check the [SessionPresent](#SessionPresent) configuration setting once connected to determine whether the server actually had any session state saved.

Refer to [CleanSession](#cleansession-property-mqtt-component), [SaveSession](#savesession-method-mqtt-component), and [RestoreSession](#restoresession-method-mqtt-component) for more information about MQTT sessions and session state persistence; refer to [WillTopic](#willtopic-property-mqtt-component), [WillMessage](#willmessage-property-mqtt-component), [WillQOS](#WillQOS), and [WillRetain](#WillRetain) for more information about MQTT Wills.

**Basic Connection Example**

```csharp
mqtt1.ClientId = "testClient";
mqtt1.CleanSession = true;
mqtt1.KeepAliveInterval = 30;
mqtt1.WillTopic = "wills/" + mqtt1.ClientId;
mqtt1.WillMessage = mqtt1.ClientId + " was disconnected ungracefully!";
mqtt1.ConnectTo("mqtt.test-server.com", 1883);
```

### Topic Subscriptions

 The [Subscribe](#subscribe-method-mqtt-component) and [Unsubscribe](#unsubscribe-method-mqtt-component) methods are used to subscribe to and unsubscribe from topics.

When subscribing, pass one or more topic filters and QoS levels to indicate the topics to subscribe to and the desired QoS level(s). Topic filters may contain wildcards in order to match multiple topics on the server.

**Subscribe Examples**

```csharp
// Subscribed event handler.
mqtt1.OnSubscribed += (s, e) => {
  if (e.ResponseCode <= 2)
    Console.WriteLine("Subscribed to " + e.TopicFilter + " at QoS " + e.QOS + ".");
  else
    Console.WriteLine("Failed to subscribe to " + e.TopicFilter + ".");
};

// Basic, subscribe to some topic filters, all at the same QoS level.
mqtt1.Subscribe("home,home/floor1/+/temperature,home/floor2/#", 2);

// A bit more advanced, subscribe to the same topic filters, but at different QoS levels.
mqtt1.Config("TopicQOSArray=1,2,2");
// The 0 is ignored here since we've specified individual QoS values explicitly.
mqtt1.Subscribe("home,home/floor1/+/temperature,home/floor2/#", 0);
```

After subscribing to topics, any messages received will cause the [MessageIn](#messagein-event-mqtt-component), and potentially also the [MessageAck](#messageack-event-mqtt-component), events to fire. Refer to those events for more information about processing steps for inbound messages.

When unsubscribing, pass the exact same topic filter that was used to subscribe.

**Unsubscribe Example**

```csharp
// Unsubscribe from topic filters; have to use the exact same strings as before. If this
// was to be called after calling the code example shown for the Subscribe() method, we
// would still be subscribed to the "home" topic filter.
mqtt1.Unsubscribe("home/floor1/+/temperature,home/floor2/#");
```

Refer to [Subscribe](#subscribe-method-mqtt-component) and [Unsubscribe](#unsubscribe-method-mqtt-component) for more information about subscriptions and topic filters.

### Publishing Messages

 To publish messages to topics, use the [PublishMessage](#publishmessage-method-mqtt-component) and [PublishData](#publishdata-method-mqtt-component) methods.

[PublishMessage](#publishmessage-method-mqtt-component) is used to publish a message with a string payload, while [PublishData](#publishdata-method-mqtt-component) is used to publish a message with a raw data payload. Both also accept the name of a topic to publish to, and a QoS level at which to publish.

**Publish Examples**

```csharp
// Publish a simple string-based message.
mqtt1.PublishMessage("/home/floor1/security/camera2", 1, "Cat detected!");

// Publish a raw data message.
byte[] catPicture = ...;
mqtt1.PublishData("/home/floor1/security/camera2", 1, catPicture);
```

Refer to [PublishData](#publishdata-method-mqtt-component) and [PublishMessage](#publishmessage-method-mqtt-component) for more information about message publishing and processing steps for outbound messages, as well as topic naming.

**MQTT 5 Notes**

MQTT 5 is similar to v3.1.1, with a few changes and several new features. Major differences include:

- The Clean Session flag functionality is divided into two properties to allow for finer control over session state data: the Clean Start flag (see [CleanSession](#cleansession-property-mqtt-component)) and the new [SessionExpInterval](#SessionExpInterval).
- All response packets (CONNACK, PUBACK, PUBREC, PUBREL, PUBCOMP, SUBACK, UNSUBACK, DISCONNECT) now contain a reason code describing why operations succeeded or failed. See [MessageAck](#messageack-event-mqtt-component), [Subscribed](#subscribed-event-mqtt-component), [Unsubscribed](#unsubscribed-event-mqtt-component), and [DisconnectReasonCode](#DisconnectReasonCode) for details.
- The Request / Response pattern is formalized by the addition of the [ResponseTopic](#ResponseTopic). Additional properties such as correlation data and be specified via [OutgoingMessageProperties](#OutgoingMessageProperties) and [ConnectProperties](#ConnectProperties).
- New subscription features: Shared Subscriptions, Subscription Options, and [SubscriptionIdentifier](#SubscriptionIdentifier) (see [Subscribe](#subscribe-method-mqtt-component) for details).
- Topic Aliases can be sent by both client and server to refer to topic filters by shorter numerical identifiers in order to save bandwidth (see [TopicAlias](#TopicAlias), [ServerTopicAliasMax](#ServerTopicAliasMax) and [ClientTopicAliasMax](#ClientTopicAliasMax)).
- Servers can communicate what features it supports in [ConnAckProperties](#ConnAckProperties).
- More: message expiration ([OutgoingMessageProperties](#OutgoingMessageProperties)), Receive Maximums and Maximum Packet Sizes ([ConnectProperties](#ConnectProperties) and [ConnAckProperties](#ConnAckProperties)), and a Will Delay interval ([WillProperties](#WillProperties)) are all supported.

## Property List

*The following is the full list of the properties of the component with short descriptions. Click on the links for further details.*

|  |  |
| --- | --- |
| [CleanSession](#cleansession-property-mqtt-component) | Determines whether a clean session is used once connected. |
| [ClientId](#clientid-property-mqtt-component) | A string that uniquely identifies this instance of the component to the server. |
| [Connected](#connected-property-mqtt-component) | Whether the component is connected. |
| [FirewallAutoDetect](#firewallautodetect-property-mqtt-component) | Whether to automatically detect and use firewall system settings, if available. |
| [FirewallType](#firewalltype-property-mqtt-component) | The type of firewall to connect through. |
| [FirewallHost](#firewallhost-property-mqtt-component) | The name or IP address of the firewall (optional). |
| [FirewallPassword](#firewallpassword-property-mqtt-component) | A password if authentication is to be used when connecting through the firewall. |
| [FirewallPort](#firewallport-property-mqtt-component) | The Transmission Control Protocol (TCP) port for the firewall Host . |
| [FirewallUser](#firewalluser-property-mqtt-component) | A username if authentication is to be used when connecting through a firewall. |
| [IncomingMessageCount](#incomingmessagecount-property-mqtt-component) | The number of records in the IncomingMessage arrays. |
| [IncomingMessageContentType](#incomingmessagecontenttype-property-mqtt-component) | String describing the content of the message. |
| [IncomingMessageCorrelationData](#incomingmessagecorrelationdata-property-mqtt-component) | Used by the sender of the request message to identify which request the response message is for when it is received. |
| [IncomingMessageDuplicate](#incomingmessageduplicate-property-mqtt-component) | Whether or not this message's Duplicate flag is set. |
| [IncomingMessageMessage](#incomingmessagemessage-property-mqtt-component) | This message's raw data payload. |
| [IncomingMessageMessageExpInterval](#incomingmessagemessageexpinterval-property-mqtt-component) | The lifetime of the message in seconds specified by the sender. |
| [IncomingMessagePacketId](#incomingmessagepacketid-property-mqtt-component) | This message's packet Id. |
| [IncomingMessagePayloadFormatIndicator](#incomingmessagepayloadformatindicator-property-mqtt-component) | Indicates whether the payload is unspecified bytes or UTF-8 Encoded character data. |
| [IncomingMessageQoS](#incomingmessageqos-property-mqtt-component) | This message's QoS level. |
| [IncomingMessageResponseTopic](#incomingmessageresponsetopic-property-mqtt-component) | String used as the topic name for a response message. |
| [IncomingMessageRetained](#incomingmessageretained-property-mqtt-component) | Whether or not this message's Retain flag is set. |
| [IncomingMessageState](#incomingmessagestate-property-mqtt-component) | This message's current state. |
| [IncomingMessageSubscriptionIdentifiers](#incomingmessagesubscriptionidentifiers-property-mqtt-component) | A comma separated list of any SubscriptionIdentifiers associated with any client subscription(s) that caused this message to be delivered. |
| [IncomingMessageTopic](#incomingmessagetopic-property-mqtt-component) | This message's topic. |
| [IncomingMessageTopicAlias](#incomingmessagetopicalias-property-mqtt-component) | An integer used to identify the topic instead of the full topic filter in order to reduce the size of the publish packet. |
| [KeepAliveInterval](#keepaliveinterval-property-mqtt-component) | The maximum period of inactivity the component will allow before sending a keep-alive packet. |
| [LocalHost](#localhost-property-mqtt-component) | The name of the local host or user-assigned IP interface through which connections are initiated or accepted. |
| [LocalPort](#localport-property-mqtt-component) | The TCP port in the local host where the component binds. |
| [OutgoingMessageCount](#outgoingmessagecount-property-mqtt-component) | The number of records in the OutgoingMessage arrays. |
| [OutgoingMessageContentType](#outgoingmessagecontenttype-property-mqtt-component) | String describing the content of the message. |
| [OutgoingMessageCorrelationData](#outgoingmessagecorrelationdata-property-mqtt-component) | Used by the sender of the request message to identify which request the response message is for when it is received. |
| [OutgoingMessageDuplicate](#outgoingmessageduplicate-property-mqtt-component) | Whether or not this message's Duplicate flag is set. |
| [OutgoingMessageMessage](#outgoingmessagemessage-property-mqtt-component) | This message's raw data payload. |
| [OutgoingMessageMessageExpInterval](#outgoingmessagemessageexpinterval-property-mqtt-component) | The lifetime of the message in seconds specified by the sender. |
| [OutgoingMessagePacketId](#outgoingmessagepacketid-property-mqtt-component) | This message's packet Id. |
| [OutgoingMessagePayloadFormatIndicator](#outgoingmessagepayloadformatindicator-property-mqtt-component) | Indicates whether the payload is unspecified bytes or UTF-8 Encoded character data. |
| [OutgoingMessageQoS](#outgoingmessageqos-property-mqtt-component) | This message's QoS level. |
| [OutgoingMessageResponseTopic](#outgoingmessageresponsetopic-property-mqtt-component) | String used as the topic name for a response message. |
| [OutgoingMessageRetained](#outgoingmessageretained-property-mqtt-component) | Whether or not this message's Retain flag is set. |
| [OutgoingMessageState](#outgoingmessagestate-property-mqtt-component) | This message's current state. |
| [OutgoingMessageSubscriptionIdentifiers](#outgoingmessagesubscriptionidentifiers-property-mqtt-component) | A comma separated list of any SubscriptionIdentifiers associated with any client subscription(s) that caused this message to be delivered. |
| [OutgoingMessageTopic](#outgoingmessagetopic-property-mqtt-component) | This message's topic. |
| [OutgoingMessageTopicAlias](#outgoingmessagetopicalias-property-mqtt-component) | An integer used to identify the topic instead of the full topic filter in order to reduce the size of the publish packet. |
| [Password](#password-property-mqtt-component) | A password if authentication is to be used. |
| [ReadyToSend](#readytosend-property-mqtt-component) | Indicates whether the component is ready to send data. |
| [RemoteHost](#remotehost-property-mqtt-component) | The address of the remote host. Domain names are resolved to IP addresses. |
| [RemotePort](#remoteport-property-mqtt-component) | The port of the MQTT server (default is 1883). The default port for SSL is 8883. |
| [SSLAcceptServerCertEffectiveDate](#sslacceptservercerteffectivedate-property-mqtt-component) | The date on which this certificate becomes valid. |
| [SSLAcceptServerCertExpirationDate](#sslacceptservercertexpirationdate-property-mqtt-component) | The date on which the certificate expires. |
| [SSLAcceptServerCertExtendedKeyUsage](#sslacceptservercertextendedkeyusage-property-mqtt-component) | A comma-delimited list of extended key usage identifiers. |
| [SSLAcceptServerCertFingerprint](#sslacceptservercertfingerprint-property-mqtt-component) | The hex-encoded, 16-byte MD5 fingerprint of the certificate. |
| [SSLAcceptServerCertFingerprintSHA1](#sslacceptservercertfingerprintsha1-property-mqtt-component) | The hex-encoded, 20-byte SHA-1 fingerprint of the certificate. |
| [SSLAcceptServerCertFingerprintSHA256](#sslacceptservercertfingerprintsha256-property-mqtt-component) | The hex-encoded, 32-byte SHA-256 fingerprint of the certificate. |
| [SSLAcceptServerCertIssuer](#sslacceptservercertissuer-property-mqtt-component) | The issuer of the certificate. |
| [SSLAcceptServerCertPrivateKey](#sslacceptservercertprivatekey-property-mqtt-component) | The private key of the certificate (if available). |
| [SSLAcceptServerCertPrivateKeyAvailable](#sslacceptservercertprivatekeyavailable-property-mqtt-component) | Whether a PrivateKey is available for the selected certificate. |
| [SSLAcceptServerCertPrivateKeyContainer](#sslacceptservercertprivatekeycontainer-property-mqtt-component) | The name of the PrivateKey container for the certificate (if available). |
| [SSLAcceptServerCertPublicKey](#sslacceptservercertpublickey-property-mqtt-component) | The public key of the certificate. |
| [SSLAcceptServerCertPublicKeyAlgorithm](#sslacceptservercertpublickeyalgorithm-property-mqtt-component) | The textual description of the certificate's public key algorithm. |
| [SSLAcceptServerCertPublicKeyLength](#sslacceptservercertpublickeylength-property-mqtt-component) | The length of the certificate's public key (in bits). |
| [SSLAcceptServerCertSerialNumber](#sslacceptservercertserialnumber-property-mqtt-component) | The serial number of the certificate encoded as a string. |
| [SSLAcceptServerCertSignatureAlgorithm](#sslacceptservercertsignaturealgorithm-property-mqtt-component) | The text description of the certificate's signature algorithm. |
| [SSLAcceptServerCertStore](#sslacceptservercertstore-property-mqtt-component) | The name of the certificate store for the client certificate. |
| [SSLAcceptServerCertStorePassword](#sslacceptservercertstorepassword-property-mqtt-component) | If the type of certificate store requires a password, this property is used to specify the password needed to open the certificate store. |
| [SSLAcceptServerCertStoreType](#sslacceptservercertstoretype-property-mqtt-component) | The type of certificate store for this certificate. |
| [SSLAcceptServerCertSubjectAltNames](#sslacceptservercertsubjectaltnames-property-mqtt-component) | Comma-separated lists of alternative subject names for the certificate. |
| [SSLAcceptServerCertThumbprintMD5](#sslacceptservercertthumbprintmd5-property-mqtt-component) | The MD5 hash of the certificate. |
| [SSLAcceptServerCertThumbprintSHA1](#sslacceptservercertthumbprintsha1-property-mqtt-component) | The SHA-1 hash of the certificate. |
| [SSLAcceptServerCertThumbprintSHA256](#sslacceptservercertthumbprintsha256-property-mqtt-component) | The SHA-256 hash of the certificate. |
| [SSLAcceptServerCertUsage](#sslacceptservercertusage-property-mqtt-component) | The text description of UsageFlags . |
| [SSLAcceptServerCertUsageFlags](#sslacceptservercertusageflags-property-mqtt-component) | The flags that show intended use for the certificate. |
| [SSLAcceptServerCertVersion](#sslacceptservercertversion-property-mqtt-component) | The certificate's version number. |
| [SSLAcceptServerCertSubject](#sslacceptservercertsubject-property-mqtt-component) | The subject of the certificate used for client authentication. |
| [SSLAcceptServerCertEncoded](#sslacceptservercertencoded-property-mqtt-component) | The certificate (PEM/Base64 encoded). |
| [SSLCertEffectiveDate](#sslcerteffectivedate-property-mqtt-component) | The date on which this certificate becomes valid. |
| [SSLCertExpirationDate](#sslcertexpirationdate-property-mqtt-component) | The date on which the certificate expires. |
| [SSLCertExtendedKeyUsage](#sslcertextendedkeyusage-property-mqtt-component) | A comma-delimited list of extended key usage identifiers. |
| [SSLCertFingerprint](#sslcertfingerprint-property-mqtt-component) | The hex-encoded, 16-byte MD5 fingerprint of the certificate. |
| [SSLCertFingerprintSHA1](#sslcertfingerprintsha1-property-mqtt-component) | The hex-encoded, 20-byte SHA-1 fingerprint of the certificate. |
| [SSLCertFingerprintSHA256](#sslcertfingerprintsha256-property-mqtt-component) | The hex-encoded, 32-byte SHA-256 fingerprint of the certificate. |
| [SSLCertIssuer](#sslcertissuer-property-mqtt-component) | The issuer of the certificate. |
| [SSLCertPrivateKey](#sslcertprivatekey-property-mqtt-component) | The private key of the certificate (if available). |
| [SSLCertPrivateKeyAvailable](#sslcertprivatekeyavailable-property-mqtt-component) | Whether a PrivateKey is available for the selected certificate. |
| [SSLCertPrivateKeyContainer](#sslcertprivatekeycontainer-property-mqtt-component) | The name of the PrivateKey container for the certificate (if available). |
| [SSLCertPublicKey](#sslcertpublickey-property-mqtt-component) | The public key of the certificate. |
| [SSLCertPublicKeyAlgorithm](#sslcertpublickeyalgorithm-property-mqtt-component) | The textual description of the certificate's public key algorithm. |
| [SSLCertPublicKeyLength](#sslcertpublickeylength-property-mqtt-component) | The length of the certificate's public key (in bits). |
| [SSLCertSerialNumber](#sslcertserialnumber-property-mqtt-component) | The serial number of the certificate encoded as a string. |
| [SSLCertSignatureAlgorithm](#sslcertsignaturealgorithm-property-mqtt-component) | The text description of the certificate's signature algorithm. |
| [SSLCertStore](#sslcertstore-property-mqtt-component) | The name of the certificate store for the client certificate. |
| [SSLCertStorePassword](#sslcertstorepassword-property-mqtt-component) | If the type of certificate store requires a password, this property is used to specify the password needed to open the certificate store. |
| [SSLCertStoreType](#sslcertstoretype-property-mqtt-component) | The type of certificate store for this certificate. |
| [SSLCertSubjectAltNames](#sslcertsubjectaltnames-property-mqtt-component) | Comma-separated lists of alternative subject names for the certificate. |
| [SSLCertThumbprintMD5](#sslcertthumbprintmd5-property-mqtt-component) | The MD5 hash of the certificate. |
| [SSLCertThumbprintSHA1](#sslcertthumbprintsha1-property-mqtt-component) | The SHA-1 hash of the certificate. |
| [SSLCertThumbprintSHA256](#sslcertthumbprintsha256-property-mqtt-component) | The SHA-256 hash of the certificate. |
| [SSLCertUsage](#sslcertusage-property-mqtt-component) | The text description of UsageFlags . |
| [SSLCertUsageFlags](#sslcertusageflags-property-mqtt-component) | The flags that show intended use for the certificate. |
| [SSLCertVersion](#sslcertversion-property-mqtt-component) | The certificate's version number. |
| [SSLCertSubject](#sslcertsubject-property-mqtt-component) | The subject of the certificate used for client authentication. |
| [SSLCertEncoded](#sslcertencoded-property-mqtt-component) | The certificate (PEM/Base64 encoded). |
| [SSLEnabled](#sslenabled-property-mqtt-component) | This property indicates whether Transport Layer Security/Secure Sockets Layer (TLS/SSL) is enabled. |
| [SSLProvider](#sslprovider-property-mqtt-component) | The Secure Sockets Layer/Transport Layer Security (SSL/TLS) implementation to use. |
| [SSLServerCertEffectiveDate](#sslservercerteffectivedate-property-mqtt-component) | The date on which this certificate becomes valid. |
| [SSLServerCertExpirationDate](#sslservercertexpirationdate-property-mqtt-component) | The date on which the certificate expires. |
| [SSLServerCertExtendedKeyUsage](#sslservercertextendedkeyusage-property-mqtt-component) | A comma-delimited list of extended key usage identifiers. |
| [SSLServerCertFingerprint](#sslservercertfingerprint-property-mqtt-component) | The hex-encoded, 16-byte MD5 fingerprint of the certificate. |
| [SSLServerCertFingerprintSHA1](#sslservercertfingerprintsha1-property-mqtt-component) | The hex-encoded, 20-byte SHA-1 fingerprint of the certificate. |
| [SSLServerCertFingerprintSHA256](#sslservercertfingerprintsha256-property-mqtt-component) | The hex-encoded, 32-byte SHA-256 fingerprint of the certificate. |
| [SSLServerCertIssuer](#sslservercertissuer-property-mqtt-component) | The issuer of the certificate. |
| [SSLServerCertPrivateKey](#sslservercertprivatekey-property-mqtt-component) | The private key of the certificate (if available). |
| [SSLServerCertPrivateKeyAvailable](#sslservercertprivatekeyavailable-property-mqtt-component) | Whether a PrivateKey is available for the selected certificate. |
| [SSLServerCertPrivateKeyContainer](#sslservercertprivatekeycontainer-property-mqtt-component) | The name of the PrivateKey container for the certificate (if available). |
| [SSLServerCertPublicKey](#sslservercertpublickey-property-mqtt-component) | The public key of the certificate. |
| [SSLServerCertPublicKeyAlgorithm](#sslservercertpublickeyalgorithm-property-mqtt-component) | The textual description of the certificate's public key algorithm. |
| [SSLServerCertPublicKeyLength](#sslservercertpublickeylength-property-mqtt-component) | The length of the certificate's public key (in bits). |
| [SSLServerCertSerialNumber](#sslservercertserialnumber-property-mqtt-component) | The serial number of the certificate encoded as a string. |
| [SSLServerCertSignatureAlgorithm](#sslservercertsignaturealgorithm-property-mqtt-component) | The text description of the certificate's signature algorithm. |
| [SSLServerCertStore](#sslservercertstore-property-mqtt-component) | The name of the certificate store for the client certificate. |
| [SSLServerCertStorePassword](#sslservercertstorepassword-property-mqtt-component) | If the type of certificate store requires a password, this property is used to specify the password needed to open the certificate store. |
| [SSLServerCertStoreType](#sslservercertstoretype-property-mqtt-component) | The type of certificate store for this certificate. |
| [SSLServerCertSubjectAltNames](#sslservercertsubjectaltnames-property-mqtt-component) | Comma-separated lists of alternative subject names for the certificate. |
| [SSLServerCertThumbprintMD5](#sslservercertthumbprintmd5-property-mqtt-component) | The MD5 hash of the certificate. |
| [SSLServerCertThumbprintSHA1](#sslservercertthumbprintsha1-property-mqtt-component) | The SHA-1 hash of the certificate. |
| [SSLServerCertThumbprintSHA256](#sslservercertthumbprintsha256-property-mqtt-component) | The SHA-256 hash of the certificate. |
| [SSLServerCertUsage](#sslservercertusage-property-mqtt-component) | The text description of UsageFlags . |
| [SSLServerCertUsageFlags](#sslservercertusageflags-property-mqtt-component) | The flags that show intended use for the certificate. |
| [SSLServerCertVersion](#sslservercertversion-property-mqtt-component) | The certificate's version number. |
| [SSLServerCertSubject](#sslservercertsubject-property-mqtt-component) | The subject of the certificate used for client authentication. |
| [SSLServerCertEncoded](#sslservercertencoded-property-mqtt-component) | The certificate (PEM/Base64 encoded). |
| [Timeout](#timeout-property-mqtt-component) | This property includes the timeout for the component. |
| [User](#user-property-mqtt-component) | A username if authentication is to be used. |
| [Version](#version-property-mqtt-component) | The MQTT protocol version that the component will conform to. |
| [WillMessage](#willmessage-property-mqtt-component) | The message that the server should publish in the event of an ungraceful disconnection. |
| [WillTopic](#willtopic-property-mqtt-component) | The topic that the server should publish the WillMessage to in the event of an ungraceful disconnection. |

## Method List

*The following is the full list of the methods of the component with short descriptions. Click on the links for further details.*

|  |  |
| --- | --- |
| [Config](#config-method-mqtt-component) | Sets or retrieves a configuration setting. |
| [Connect](#connect-method-mqtt-component) | Connects to the remote host. |
| [ConnectTo](#connectto-method-mqtt-component) | Connects to the remote host. |
| [Disconnect](#disconnect-method-mqtt-component) | This method disconnects from the remote host. |
| [DoEvents](#doevents-method-mqtt-component) | This method processes events from the internal message queue. |
| [Interrupt](#interrupt-method-mqtt-component) | Interrupt the current action and disconnects from the remote host. |
| [PublishData](#publishdata-method-mqtt-component) | Publishes a message with a raw data payload. |
| [PublishMessage](#publishmessage-method-mqtt-component) | Publishes a message with a string payload. |
| [Reset](#reset-method-mqtt-component) | This method will reset the component. |
| [RestoreSession](#restoresession-method-mqtt-component) | Restores session state data. |
| [SaveSession](#savesession-method-mqtt-component) | Saves session state data. |
| [Subscribe](#subscribe-method-mqtt-component) | Subscribes the component to one or more topic filters. |
| [Unsubscribe](#unsubscribe-method-mqtt-component) | Unsubscribes the component from one or more topic filters. |

## Event List

*The following is the full list of the events fired by the component with short descriptions. Click on the links for further details.*

|  |  |
| --- | --- |
| [Connected](#connected-event-mqtt-component) | Fired immediately after a connection completes (or fails). |
| [ConnectionStatus](#connectionstatus-event-mqtt-component) | Fired to indicate changes in the connection state. |
| [Disconnected](#disconnected-event-mqtt-component) | Fired when a connection is closed. |
| [Error](#error-event-mqtt-component) | Fired when information is available about errors during data delivery. |
| [Log](#log-event-mqtt-component) | Fires once for each log message. |
| [MessageAck](#messageack-event-mqtt-component) | Fired when an incoming or outgoing message has completed all acknowledgment steps. |
| [MessageIn](#messagein-event-mqtt-component) | Fired when an incoming message has been received and/or fully acknowledged. |
| [MessageOut](#messageout-event-mqtt-component) | Fired when an outgoing message has been sent and/or fully acknowledged. |
| [ReadyToSend](#readytosend-event-mqtt-component) | Fired when the component is ready to send data. |
| [SSLServerAuthentication](#sslserverauthentication-event-mqtt-component) | Fired after the server presents its certificate to the client. |
| [SSLStatus](#sslstatus-event-mqtt-component) | Fired when secure connection progress messages are available. |
| [Subscribed](#subscribed-event-mqtt-component) | Fires for each topic filter subscription the server acknowledges. |
| [Unsubscribed](#unsubscribed-event-mqtt-component) | Fires when the server has acknowledged an unsubscribe request. |

## Config Settings

*The following is a list of config settings for the component with short descriptions. Click on the links for further details.*

|  |  |
| --- | --- |
| [AutoReconnect](#AutoReconnect) | Whether to automatically attempt to reconnect in the event of a connection error. |
| [ClientTopicAliasMax](#ClientTopicAliasMax) | The maximum value the client will accept for a topic alias sent by the server. |
| [ConnAckProperties](#ConnAckProperties) | JSON string containing the properties returned in the CONNACK packet. |
| [ConnectionTimeout](#ConnectionTimeout) | How long to wait for a connection attempt to succeed. |
| [ConnectProperties](#ConnectProperties) | JSON string specifying properties to be included in the CONNECT packet. |
| [DisconnectProperties](#DisconnectProperties) | JSON string containing DISCONNECT packet properties. |
| [DisconnectReasonCode](#DisconnectReasonCode) | Code describing the reason the client or server closed the connection. |
| [Duplicate](#Duplicate) | Whether to set the Duplicate flag when publishing a message. |
| [IncomingUserPropCount](#IncomingUserPropCount) | The size of the IncomingUserPropName and IncomingUserPropValue arrays. |
| [IncomingUserPropName\[i\]](#IncomingUserPropName[i]) | The name of the user property at index i. |
| [IncomingUserPropValue\[i\]](#IncomingUserPropValue[i]) | The value of the user property at index i. |
| [LogLevel](#LogLevel) | The level of detail that is logged. |
| [OutgoingMessageProperties](#OutgoingMessageProperties) | JSON string specifying properties to be included in the PUBLISH packet. |
| [OutgoingPacketId](#OutgoingPacketId) | The packet Id of the last message published. |
| [OutgoingUserPropCount](#OutgoingUserPropCount) | Controls the size of the OutgoingUserPropName and OutgoingUserPropValue configuration arrays. |
| [OutgoingUserPropName\[i\]](#OutgoingUserPropName[i]) | The name of the User Property at index i. |
| [OutgoingUserPropValue\[i\]](#OutgoingUserPropValue[i]) | The value of the User Property at index i. |
| [RepublishInterval](#RepublishInterval) | How many seconds to wait before republishing unacknowledged messages. |
| [ResponseTopic](#ResponseTopic) | Topic name for a response message. |
| [Retain](#Retain) | Whether to set the Retain flag when publishing a message. |
| [SendCustomPacket](#SendCustomPacket) | Sends a packet constructed using the supplied hex byte string. |
| [ServerTopicAliasMax](#ServerTopicAliasMax) | The highest value that the Server will accept as a Topic Alias sent by the Client. |
| [SessionExpInterval](#SessionExpInterval) | The length of time in seconds the client and server should store session state data after the connection is closed. |
| [SessionPresent](#SessionPresent) | When connecting with CleanSession disabled, indicates whether the server actually had any previous session data stored. |
| [SessionStateFile](#SessionStateFile) | File to use for saving and restoring session data. |
| [SubscriptionIdentifier](#SubscriptionIdentifier) | A numeric subscription identifier included in SUBSCRIBE packet which will be returned with messages delivered for that subscription. |
| [TopicAlias](#TopicAlias) | Value that is used to identify the Topic instead of using the Topic Name in order to reduce packet size. |
| [TopicDelimiter](#TopicDelimiter) | The string to use as a delimiter in a topic filter list string. |
| [TopicNLArray](#TopicNLArray) | List of No Local option flags for subscription topic filters. |
| [TopicQOSArray](#TopicQOSArray) | Comma-separated list of topic filter QoS values to use when subscribing. |
| [TopicRAPArray](#TopicRAPArray) | List of Retain As Published option flags for subscription topic filters. |
| [TopicRHArray](#TopicRHArray) | List of Retain Handling option values for subscription topic filters. |
| [WillProperties](#WillProperties) | JSON string specifying will properties to be included in the CONNECT packet. |
| [WillQOS](#WillQOS) | The QoS value to use for the Will message. |
| [WillRetain](#WillRetain) | Whether the server should retain the Will message after publishing it. |
| [ConnectionTimeout](#ConnectionTimeout) | Sets a separate timeout value for establishing a connection. |
| [EnableFallback](#EnableFallback) | Whether to try the other addresses the remote host resolves to when a connection attempt fails. |
| [FallbackTimeout](#FallbackTimeout) | The maximum time in milliseconds to spend on connection attempts when EnableFallback is enabled. |
| [FirewallAutoDetect](#FirewallAutoDetect) | Tells the component whether or not to automatically detect and use firewall system settings, if available. |
| [FirewallHost](#FirewallHost) | Name or IP address of firewall (optional). |
| [FirewallHTTPVersion](#FirewallHTTPVersion) | The HTTP version to be used when connecting through a tunneling proxy. |
| [FirewallPassword](#FirewallPassword) | Password to be used if authentication is to be used when connecting through the firewall. |
| [FirewallPort](#FirewallPort) | The TCP port for the FirewallHost;. |
| [FirewallType](#FirewallType) | Determines the type of firewall to connect through. |
| [FirewallUser](#FirewallUser) | A user name if authentication is to be used connecting through a firewall. |
| [KeepAliveInterval](#KeepAliveInterval) | The retry interval, in milliseconds, to be used when a TCP keep-alive packet is sent and no response is received. |
| [KeepAliveTime](#KeepAliveTime) | The inactivity time in milliseconds before a TCP keep-alive packet is sent. |
| [Linger](#Linger) | When set to True, connections are terminated gracefully. |
| [LingerTime](#LingerTime) | Time in seconds to have the connection linger. |
| [LocalHost](#LocalHost) | The name of the local host through which connections are initiated or accepted. |
| [LocalPort](#LocalPort) | The port in the local host where the component binds. |
| [MaxLineLength](#MaxLineLength) | The maximum amount of data to accumulate when no EOL is found. |
| [MaxTransferRate](#MaxTransferRate) | The transfer rate limit in bytes per second. |
| [ProxyExceptionsList](#ProxyExceptionsList) | A semicolon separated list of hosts and IPs to bypass when using a proxy. |
| [TCPKeepAlive](#TCPKeepAlive) | Determines whether or not the keep alive socket option is enabled. |
| [TcpNoDelay](#TcpNoDelay) | Whether or not to delay when sending packets. |
| [UseIPv6](#UseIPv6) | Whether to use IPv6. |
| [UseNTLMv2](#UseNTLMv2) | Whether to use NTLM V2. |
| [LogSSLPackets](#LogSSLPackets) | Controls whether SSL packets are logged when using the internal security API. |
| [OpenSSLCADir](#OpenSSLCADir) | The path to a directory containing CA certificates. |
| [OpenSSLCAFile](#OpenSSLCAFile) | Name of the file containing the list of CA's trusted by your application. |
| [OpenSSLCipherList](#OpenSSLCipherList) | A string that controls the ciphers to be used by SSL. |
| [OpenSSLPrngSeedData](#OpenSSLPrngSeedData) | The data to seed the pseudo random number generator (PRNG). |
| [ReuseSSLSession](#ReuseSSLSession) | Determines if the SSL session is reused. |
| [SSLCACerts](#SSLCACerts) | A newline separated list of CA certificates to be included when performing an SSL handshake. |
| [SSLCheckCRL](#SSLCheckCRL) | Whether to check the Certificate Revocation List for the server certificate. |
| [SSLCheckOCSP](#SSLCheckOCSP) | Whether to use OCSP to check the status of the server certificate. |
| [SSLCipherStrength](#SSLCipherStrength) | The minimum cipher strength used for bulk encryption. |
| [SSLClientCACerts](#SSLClientCACerts) | A newline separated list of CA certificates to use during SSL client certificate validation. |
| [SSLEnabledCipherSuites](#SSLEnabledCipherSuites) | The cipher suite to be used in an SSL negotiation. |
| [SSLEnabledProtocols](#SSLEnabledProtocols) | Used to enable/disable the supported security protocols. |
| [SSLEnableRenegotiation](#SSLEnableRenegotiation) | Whether the renegotiation_info SSL extension is supported. |
| [SSLIncludeCertChain](#SSLIncludeCertChain) | Whether the entire certificate chain is included in the SSLServerAuthentication event. |
| [SSLKeyLogFile](#SSLKeyLogFile) | The location of a file where per-session secrets are written for debugging purposes. |
| [SSLNegotiatedCipher](#SSLNegotiatedCipher) | Returns the negotiated cipher suite. |
| [SSLNegotiatedCipherStrength](#SSLNegotiatedCipherStrength) | Returns the negotiated cipher suite strength. |
| [SSLNegotiatedCipherSuite](#SSLNegotiatedCipherSuite) | Returns the negotiated cipher suite. |
| [SSLNegotiatedKeyExchange](#SSLNegotiatedKeyExchange) | Returns the negotiated key exchange algorithm. |
| [SSLNegotiatedKeyExchangeStrength](#SSLNegotiatedKeyExchangeStrength) | Returns the negotiated key exchange algorithm strength. |
| [SSLNegotiatedVersion](#SSLNegotiatedVersion) | Returns the negotiated protocol version. |
| [SSLSecurityFlags](#SSLSecurityFlags) | Flags that control certificate verification. |
| [SSLServerCACerts](#SSLServerCACerts) | A newline separated list of CA certificates to use during SSL server certificate validation. |
| [TLS12SignatureAlgorithms](#TLS12SignatureAlgorithms) | Defines the allowed TLS 1.2 signature algorithms when SSLProvider is set to Internal. |
| [TLS12SupportedGroups](#TLS12SupportedGroups) | The supported groups for ECC. |
| [TLS13KeyShareGroups](#TLS13KeyShareGroups) | The groups for which to pregenerate key shares. |
| [TLS13SignatureAlgorithms](#TLS13SignatureAlgorithms) | The allowed certificate signature algorithms. |
| [TLS13SupportedGroups](#TLS13SupportedGroups) | The supported groups for (EC)DHE key exchange. |
| [AbsoluteTimeout](#AbsoluteTimeout) | Determines whether timeouts are inactivity timeouts or absolute timeouts. |
| [FirewallData](#FirewallData) | Used to send extra data to the firewall. |
| [InBufferSize](#InBufferSize) | The size in bytes of the incoming queue of the socket. |
| [OutBufferSize](#OutBufferSize) | The size in bytes of the outgoing queue of the socket. |
| [BuildInfo](#BuildInfo) | Information about the product's build. |
| [CodePage](#CodePage) | The system code page used for Unicode to Multibyte translations. |
| [LicenseInfo](#LicenseInfo) | Information about the current license. |
| [MaskSensitiveData](#MaskSensitiveData) | Whether sensitive data is masked in log messages. |
| [UseFIPSCompliantAPI](#UseFIPSCompliantAPI) | Tells the component whether or not to use FIPS certified APIs. |
| [UseInternalSecurityAPI](#UseInternalSecurityAPI) | Whether or not to use the system security libraries or an internal implementation. |

# CleanSession Property ([MQTT](#mqtt-component) Component)

Determines whether a clean session is used once connected.

## Syntax

*C++ Builder Syntax*

```text
__property bool CleanSession = { read=FCleanSession, write=FSetCleanSession };
```

## Default Value

true

## Remarks

This property determines whether or not the component should instruct the server to use a clean session when it connects. (Note that this property must be set to the desired value *before* calling [Connect](#connect-method-mqtt-component).)

By default, CleanSession is true, so the server will discard any state data previously associated with the current [ClientId](#clientid-property-mqtt-component) once the component has connected successfully. In addition, the server will not save any state data when the component disconnects.

Setting CleanSession to *False* before connecting will cause the server to re-associate any previously stored state data for the current [ClientId](#clientid-property-mqtt-component). The server will also save any state data that exists when the component is disconnected.

The server-side session state consists of:

- whether a session is present (see [SessionPresent](#SessionPresent)),
- client subscriptions (including subscription identifiers in MQTT 5),
- QoS 1 and 2 messages sent to the client pending transmission or completed acknowledgment (and optionally pending QoS 0 messages),
- QoS 2 messages received from the client but not completely acknowledged, and
- the [SessionExpInterval](#SessionExpInterval) (in MQTT 5).

Note that retained messages are not deleted as a result of a session ending, but are not part of the session state.

### Client-Side Session State

When setting CleanSession to *False*, it is important that the [RestoreSession](#restoresession-method-mqtt-component) method be used to load any previously saved (client-side) session data from a previous session before calling [Connect](#connect-method-mqtt-component). (Successful calls to [RestoreSession](#restoresession-method-mqtt-component) will automatically set CleanSession to *False*.)

Similarly, once disconnected, save the string returned by [SaveSession](#savesession-method-mqtt-component) for later use. The saved session information may be used when connecting with CleanSession set to *False* at a later time.

The client-side session state consists of:

- QoS 1 and QoS 2 messages which have been sent to the Server, but have not been completely acknowledged, and
- QoS 2 messages which have been received from the Server, but have not been completely acknowledged.

Refer to [SaveSession](#savesession-method-mqtt-component) and [RestoreSession](#restoresession-method-mqtt-component) for more information.

**MQTT 5 Notes**

In MQTT 5, the "Clean Session" flag from v3.1.1 is split into a "Clean Start" flag indicating that the server should discard previously saved session data from this connection, and a [SessionExpInterval](#SessionExpInterval) controlling the length of time the server should preserve the session data after disconnection.

In MQTT 5, this property acts only as the "Clean Start" flag. It determines whether or not the component should instruct the server to discard any previously stored session data associated with the current [ClientId](#clientid-property-mqtt-component) and start a new clean session.

For more information on session expiration in MQTT 5, see the [SessionExpInterval](#SessionExpInterval) config. Setting CleanSession to *True* in v3.1.1 is equivalent to setting CleanSession to *True* AND setting [SessionExpInterval](#SessionExpInterval) to *0* in MQTT 5.

As with MQTT 3.1.1, it is important for the client to save and restore its own session data on connection and disconnection depending on the value of CleanSession, and to manage its preservation depending on [SessionExpInterval](#SessionExpInterval).

This property is not available at design time.

## Data Type

Boolean

# ClientId Property ([MQTT](#mqtt-component) Component)

A string that uniquely identifies this instance of the component to the server.

## Syntax

*C++ Builder Syntax*

```text
__property String ClientId = { read=FClientId, write=FSetClientId };
```

## Default Value

""

## Remarks

The ClientId string is used by the server to uniquely identify each client that is connected to it. In MQTT 5, when the [SessionExpInterval](#SessionExpInterval) config is set to a positive value, the server will also associate it with any session state data that needs to be saved for the length of time specified when the component is disconnected.

If ClientId is empty when [Connect](#connect-method-mqtt-component) is called, the component's behavior depends on value of [CleanSession](#cleansession-property-mqtt-component). If [CleanSession](#cleansession-property-mqtt-component) is *True*, the component will automatically generate a unique value for ClientId before connecting. If [CleanSession](#cleansession-property-mqtt-component) is *False*, the component raises an exception.

This property is not available at design time.

## Data Type

String

# Connected Property ([MQTT](#mqtt-component) Component)

Whether the component is connected.

## Syntax

*C++ Builder Syntax*

```text
__property bool Connected = { read=FConnected };
```

## Default Value

False

## Remarks

This property is used to determine whether or not the component is connected to the remote host. By default the component will connect in plaintext. To enable SSL set [SSLEnabled](#sslenabled-property-mqtt-component) to True.

In addition, WebSocket connections are supported. To connect using WebSockets specify a hostname beginning with *ws://* (plaintext) or *wss://* (SSL). For instance, *ws://test.mosquitto.org*.

When connecting to an MQTT server, the component sends the following information:

- The values of the [ClientId](#clientid-property-mqtt-component), [CleanSession](#cleansession-property-mqtt-component), and [KeepAliveInterval](#keepaliveinterval-property-mqtt-component) properties.
- The value of the [User](#user-property-mqtt-component) property (if non-empty).
- The value of the [Password](#password-property-mqtt-component) property (if non-empty).
- The values of the [WillTopic](#willtopic-property-mqtt-component) and [WillMessage](#willmessage-property-mqtt-component) properties and the [WillQOS](#WillQOS) and [WillRetain](#WillRetain) configuration settings.
- MQTT 5 specific values from [ClientTopicAliasMax](#ClientTopicAliasMax), [SessionExpInterval](#SessionExpInterval), [ConnectProperties](#ConnectProperties) and [WillProperties](#WillProperties).

If [CleanSession](#cleansession-property-mqtt-component) is *True*, check the [SessionPresent](#SessionPresent) configuration setting once connected to determine whether the server actually had any session state saved.

Refer to [CleanSession](#cleansession-property-mqtt-component), [SaveSession](#savesession-method-mqtt-component), and [RestoreSession](#restoresession-method-mqtt-component) for more information about MQTT sessions and session state persistence; refer to [WillTopic](#willtopic-property-mqtt-component), [WillMessage](#willmessage-property-mqtt-component), [WillQOS](#WillQOS), and [WillRetain](#WillRetain) for more information about MQTT Wills.

**Basic Connection Example**

```csharp
mqtt1.ClientId = "testClient";
mqtt1.CleanSession = true;
mqtt1.KeepAliveInterval = 30;
mqtt1.WillTopic = "wills/" + mqtt1.ClientId;
mqtt1.WillMessage = mqtt1.ClientId + " was disconnected ungracefully!";
mqtt1.RemoteHost = "mqtt.test-server.com";
mqtt1.RemotePort = 1883;
mqtt1.Connect();
```

This property is read-only and not available at design time.

## Data Type

Boolean

# FirewallAutoDetect Property ([MQTT](#mqtt-component) Component)

Whether to automatically detect and use firewall system settings, if available.

## Syntax

*C++ Builder Syntax*

```text
__property bool FirewallAutoDetect = { read=FFirewallAutoDetect, write=FSetFirewallAutoDetect };
```

## Default Value

False

## Remarks

Whether to automatically detect and use firewall system settings, if available.

## Data Type

Boolean

# FirewallType Property ([MQTT](#mqtt-component) Component)

The type of firewall to connect through.

## Syntax

*C++ Builder Syntax*

```text
__property TiotMQTTFirewallTypes FirewallType = { read=FFirewallType, write=FSetFirewallType };
enum TiotMQTTFirewallTypes {
  fwNone=0,
  fwTunnel=1,
  fwSOCKS4=2,
  fwSOCKS5=3,
  fwSOCKS4A=10
};
```

## Default Value

fwNone

## Remarks

The type of firewall to connect through. The applicable values are as follows:

|  |  |
| --- | --- |
| fwNone (0) | No firewall (default setting). |
| fwTunnel (1) | Connect through a tunneling proxy. [FirewallPort](#firewallport-property-mqtt-component) is set to 80. |
| fwSOCKS4 (2) | Connect through a SOCKS4 Proxy. [FirewallPort](#firewallport-property-mqtt-component) is set to 1080. |
| fwSOCKS5 (3) | Connect through a SOCKS5 Proxy. [FirewallPort](#firewallport-property-mqtt-component) is set to 1080. |
| fwSOCKS4A (10) | Connect through a SOCKS4A Proxy. [FirewallPort](#firewallport-property-mqtt-component) is set to 1080. |

## Data Type

Integer

# FirewallHost Property ([MQTT](#mqtt-component) Component)

The name or IP address of the firewall (optional).

## Syntax

*C++ Builder Syntax*

```text
__property String FirewallHost = { read=FFirewallHost, write=FSetFirewallHost };
```

## Default Value

""

## Remarks

The name or IP address of the firewall (optional). If a [FirewallHost](#firewallhost-property-mqtt-component) is given, the requested connections will be authenticated through the specified firewall when connecting.

If this property is set to a Domain Name, a DNS request is initiated. Upon successful termination of the request, this property is set to the corresponding address. If the search is not successful, the component raises an exception.

## Data Type

String

# FirewallPassword Property ([MQTT](#mqtt-component) Component)

A password if authentication is to be used when connecting through the firewall.

## Syntax

*C++ Builder Syntax*

```text
__property String FirewallPassword = { read=FFirewallPassword, write=FSetFirewallPassword };
```

## Default Value

""

## Remarks

A password if authentication is to be used when connecting through the firewall. If [FirewallHost](#firewallhost-property-mqtt-component) is specified, the [FirewallUser](#firewalluser-property-mqtt-component) and [FirewallPassword](#firewallpassword-property-mqtt-component) properties are used to connect and authenticate to the given firewall. If the authentication fails, the component raises an exception.

## Data Type

String

# FirewallPort Property ([MQTT](#mqtt-component) Component)

The Transmission Control Protocol (TCP) port for the firewall Host .

## Syntax

*C++ Builder Syntax*

```text
__property int FirewallPort = { read=FFirewallPort, write=FSetFirewallPort };
```

## Default Value

0

## Remarks

The Transmission Control Protocol (TCP) port for the firewall [FirewallHost](#firewallhost-property-mqtt-component). See the description of the [FirewallHost](#firewallhost-property-mqtt-component) property for details.

NOTE: This property is set automatically when [FirewallType](#firewalltype-property-mqtt-component) is set to a valid value. See the description of the [FirewallType](#firewalltype-property-mqtt-component) property for details.

## Data Type

Integer

# FirewallUser Property ([MQTT](#mqtt-component) Component)

A username if authentication is to be used when connecting through a firewall.

## Syntax

*C++ Builder Syntax*

```text
__property String FirewallUser = { read=FFirewallUser, write=FSetFirewallUser };
```

## Default Value

""

## Remarks

A username if authentication is to be used when connecting through a firewall. If [FirewallHost](#firewallhost-property-mqtt-component) is specified, this property and the [FirewallPassword](#firewallpassword-property-mqtt-component) property are used to connect and authenticate to the given [Firewall](#Type_Firewall). If the authentication fails, the component raises an exception.

## Data Type

String

# IncomingMessageCount Property ([MQTT](#mqtt-component) Component)

The number of records in the IncomingMessage arrays.

## Syntax

*C++ Builder Syntax*

```text
__property int IncomingMessageCount = { read=FIncomingMessageCount };
```

## Default Value

0

## Remarks

This property controls the size of the following arrays:

- [IncomingMessageContentType](#incomingmessagecontenttype-property-mqtt-component)
- [IncomingMessageCorrelationData](#incomingmessagecorrelationdata-property-mqtt-component)
- [IncomingMessageDuplicate](#incomingmessageduplicate-property-mqtt-component)
- [IncomingMessageMessage](#incomingmessagemessage-property-mqtt-component)
- [IncomingMessageMessageExpInterval](#incomingmessagemessageexpinterval-property-mqtt-component)
- [IncomingMessagePacketId](#incomingmessagepacketid-property-mqtt-component)
- [IncomingMessagePayloadFormatIndicator](#incomingmessagepayloadformatindicator-property-mqtt-component)
- [IncomingMessageQoS](#incomingmessageqos-property-mqtt-component)
- [IncomingMessageResponseTopic](#incomingmessageresponsetopic-property-mqtt-component)
- [IncomingMessageRetained](#incomingmessageretained-property-mqtt-component)
- [IncomingMessageState](#incomingmessagestate-property-mqtt-component)
- [IncomingMessageSubscriptionIdentifiers](#incomingmessagesubscriptionidentifiers-property-mqtt-component)
- [IncomingMessageTopic](#incomingmessagetopic-property-mqtt-component)
- [IncomingMessageTopicAlias](#incomingmessagetopicalias-property-mqtt-component)

The array indices start at *0* and end at *IncomingMessageCount - 1*.

This property is read-only and not available at design time.

## Data Type

Integer

# IncomingMessageContentType Property ([MQTT](#mqtt-component) Component)

String describing the content of the message.

## Syntax

*C++ Builder Syntax*

```text
__property String IncomingMessageContentType[int IncomingMessageIndex] = { read=FIncomingMessageContentType };
```

## Default Value

""

## Remarks

String describing the content of the message. Defined by the sending and receiving application.

Valid only for MQTT 5.

The *IncomingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [IncomingMessageCount](#incomingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

String

# IncomingMessageCorrelationData Property ([MQTT](#mqtt-component) Component)

Used by the sender of the request message to identify which request the response message is for when it is received.

## Syntax

*C++ Builder Syntax*

```text
__property String IncomingMessageCorrelationData[int IncomingMessageIndex] = { read=FIncomingMessageCorrelationData };
```

## Default Value

""

## Remarks

Used by the sender of the request message to identify which request the response message is for when it is received.

Valid only for MQTT 5.

The *IncomingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [IncomingMessageCount](#incomingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

String

# IncomingMessageDuplicate Property ([MQTT](#mqtt-component) Component)

Whether or not this message's Duplicate flag is set.

## Syntax

*C++ Builder Syntax*

```text
__property bool IncomingMessageDuplicate[int IncomingMessageIndex] = { read=FIncomingMessageDuplicate };
```

## Default Value

false

## Remarks

Whether or not this message's Duplicate flag is set.

The *IncomingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [IncomingMessageCount](#incomingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

Boolean

# IncomingMessageMessage Property ([MQTT](#mqtt-component) Component)

This message's raw data payload.

## Syntax

*C++ Builder Syntax*

```text
__property String IncomingMessageMessage[int IncomingMessageIndex] = { read=FIncomingMessageMessage };
__property DynamicArray<Byte> IncomingMessageMessageB[int IncomingMessageIndex] = { read=FIncomingMessageMessageB };
```

## Default Value

""

## Remarks

This message's raw data payload.

The *IncomingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [IncomingMessageCount](#incomingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

Byte Array

# IncomingMessageMessageExpInterval Property ([MQTT](#mqtt-component) Component)

The lifetime of the message in seconds specified by the sender.

## Syntax

*C++ Builder Syntax*

```text
__property int IncomingMessageMessageExpInterval[int IncomingMessageIndex] = { read=FIncomingMessageMessageExpInterval };
```

## Default Value

0

## Remarks

The lifetime of the message in seconds specified by the sender.

For outgoing messages, the value is useful for instructing the server to delete its copies of the message for any subscribers it has not been able to start delivery to.

For incoming messages, the value sent by the server is the lifetime specified by the sender minus the time the message has been waiting in the server.

Valid only for MQTT 5.

The *IncomingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [IncomingMessageCount](#incomingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

Integer

# IncomingMessagePacketId Property ([MQTT](#mqtt-component) Component)

This message's packet Id.

## Syntax

*C++ Builder Syntax*

```text
__property int IncomingMessagePacketId[int IncomingMessageIndex] = { read=FIncomingMessagePacketId };
```

## Default Value

0

## Remarks

This message's packet Id.

The *IncomingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [IncomingMessageCount](#incomingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

Integer

# IncomingMessagePayloadFormatIndicator Property ([MQTT](#mqtt-component) Component)

Indicates whether the payload is unspecified bytes or UTF-8 Encoded character data.

## Syntax

*C++ Builder Syntax*

```text
__property int IncomingMessagePayloadFormatIndicator[int IncomingMessageIndex] = { read=FIncomingMessagePayloadFormatIndicator };
```

## Default Value

0

## Remarks

Indicates whether the payload is unspecified bytes or UTF-8 Encoded character data. Possible values are:

|  |  |
| --- | --- |
| Value | Description |
| 0 | Payload is unspecified bytes |
| 1 | Payload is UTF-8 Encoded Character Data |

Valid only for MQTT 5.

The *IncomingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [IncomingMessageCount](#incomingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

Integer

# IncomingMessageQoS Property ([MQTT](#mqtt-component) Component)

This message's QoS level.

## Syntax

*C++ Builder Syntax*

```text
__property int IncomingMessageQoS[int IncomingMessageIndex] = { read=FIncomingMessageQoS };
```

## Default Value

0

## Remarks

This message's QoS level. Possible values are:

|  |  |
| --- | --- |
| Value | Description |
| 0 | At most once delivery |
| 1 | At least once delivery |
| 2 | Exactly once delivery |

The *IncomingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [IncomingMessageCount](#incomingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

Integer

# IncomingMessageResponseTopic Property ([MQTT](#mqtt-component) Component)

String used as the topic name for a response message.

## Syntax

*C++ Builder Syntax*

```text
__property String IncomingMessageResponseTopic[int IncomingMessageIndex] = { read=FIncomingMessageResponseTopic };
```

## Default Value

""

## Remarks

String used as the topic name for a response message.

Valid only for MQTT 5.

The *IncomingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [IncomingMessageCount](#incomingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

String

# IncomingMessageRetained Property ([MQTT](#mqtt-component) Component)

Whether or not this message's Retain flag is set.

## Syntax

*C++ Builder Syntax*

```text
__property bool IncomingMessageRetained[int IncomingMessageIndex] = { read=FIncomingMessageRetained };
```

## Default Value

false

## Remarks

Whether or not this message's Retain flag is set.

The *IncomingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [IncomingMessageCount](#incomingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

Boolean

# IncomingMessageState Property ([MQTT](#mqtt-component) Component)

This message's current state.

## Syntax

*C++ Builder Syntax*

```text
__property int IncomingMessageState[int IncomingMessageIndex] = { read=FIncomingMessageState };
```

## Default Value

0

## Remarks

This message's current state.

**Possible Outgoing Message States:**

|  |  |
| --- | --- |
| Value | Description |
| 0 | PUBLISH sent, waiting for PUBACK (QoS 1 only) |
| 1 | PUBLISH sent, waiting for PUBREC (QoS 2 only) |
| 2 | PUBREC received, sending PUBREL (QoS 2 only) |
| 3 | PUBREL sent, waiting for PUBCOMP (QoS 2 only) |
| 4 | Final acknowledgment received |

**Possible Incoming Message States:**

|  |  |
| --- | --- |
| Value | Description |
| 5 | PUBLISH received, sending PUBACK (QoS 1 only) |
| 6 | PUBLISH received, sending PUBREC (QoS 2 only) |
| 7 | PUBREC sent, waiting for PUBREL (QoS 2 only) |
| 8 | PUBREL received, sending PUBCOMP (QoS 2 only) |
| 9 | Final acknowledgment sent |

The *IncomingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [IncomingMessageCount](#incomingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

Integer

# IncomingMessageSubscriptionIdentifiers Property ([MQTT](#mqtt-component) Component)

A comma separated list of any SubscriptionIdentifiers associated with any client subscription(s) that caused this message to be delivered.

## Syntax

*C++ Builder Syntax*

```text
__property String IncomingMessageSubscriptionIdentifiers[int IncomingMessageIndex] = { read=FIncomingMessageSubscriptionIdentifiers };
```

## Default Value

""

## Remarks

A comma separated list of any SubscriptionIdentifiers associated with any client subscription(s) that caused this message to be delivered.

This property is only applicable to incoming messages.

If [SubscriptionIdentifier](#SubscriptionIdentifier) is set when subscribing, it will be included in any messages delivered by the broker for the topics specified in that packet.

See the [Subscribe](#subscribe-method-mqtt-component) method for more details.

Valid only for MQTT 5.

The *IncomingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [IncomingMessageCount](#incomingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

String

# IncomingMessageTopic Property ([MQTT](#mqtt-component) Component)

This message's topic.

## Syntax

*C++ Builder Syntax*

```text
__property String IncomingMessageTopic[int IncomingMessageIndex] = { read=FIncomingMessageTopic };
```

## Default Value

""

## Remarks

This message's topic.

**MQTT 5 Notes:**

If this value is empty, the [IncomingMessageTopicAlias](#incomingmessagetopicalias-property-mqtt-component) property holds the assigned alias for the topic.

If this value is not empty and [IncomingMessageTopicAlias](#incomingmessagetopicalias-property-mqtt-component) is non-zero,

The *IncomingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [IncomingMessageCount](#incomingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

String

# IncomingMessageTopicAlias Property ([MQTT](#mqtt-component) Component)

An integer used to identify the topic instead of the full topic filter in order to reduce the size of the publish packet.

## Syntax

*C++ Builder Syntax*

```text
__property int IncomingMessageTopicAlias[int IncomingMessageIndex] = { read=FIncomingMessageTopicAlias };
```

## Default Value

0

## Remarks

An integer used to identify the topic instead of the full topic filter in order to reduce the size of the publish packet.

If a non-zero topic alias is received, the client should establish a new topic alias mapping or use an existing mapping, depending on whether the [IncomingMessageTopic](#incomingmessagetopic-property-mqtt-component) string is empty.

For details on setting topic aliases for outgoing messages, see the [TopicAlias](#TopicAlias) configuration setting.

Valid only for MQTT 5.

The *IncomingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [IncomingMessageCount](#incomingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

Integer

# KeepAliveInterval Property ([MQTT](#mqtt-component) Component)

The maximum period of inactivity the component will allow before sending a keep-alive packet.

## Syntax

*C++ Builder Syntax*

```text
__property int KeepAliveInterval = { read=FKeepAliveInterval, write=FSetKeepAliveInterval };
```

## Default Value

0

## Remarks

The KeepAliveInterval, if set to a non-zero value, is the maximum number of seconds that the component will allow the connection to be idle before sending a PINGREQ (ping request) packet to the server. The value of KeepAliveInterval is sent to the server when [Connect](#connect-method-mqtt-component) is called; it cannot be changed when the component is already connected.

MQTT servers are required to measure periods of inactivity for all clients who specify a non-zero KeepAliveInterval, and must disconnect them if they have not communicated within 1.5 times KeepAliveInterval.

Similarly, if the component doesn't receive a PINGRESP (ping response) packet within KeepAliveInterval seconds after sending a PINGREQ packet, it will disconnect from the server.

If KeepAliveInterval is set to 0 (default), keep-alive functionality is disabled entirely. In this case, the component will not send any PINGREQ packets, and the server is not required to close the connection due to inactivity.

Note that, regardless of keep-alive settings, the server is always free to disconnect clients it deems "unresponsive".

This property is not available at design time.

## Data Type

Integer

# LocalHost Property ([MQTT](#mqtt-component) Component)

The name of the local host or user-assigned IP interface through which connections are initiated or accepted.

## Syntax

*C++ Builder Syntax*

```text
__property String LocalHost = { read=FLocalHost, write=FSetLocalHost };
```

## Default Value

""

## Remarks

This property contains the name of the local host as obtained by the *gethostname()* system call, or if the user has assigned an IP address, the value of that address.

In multihomed hosts (machines with more than one IP interface) setting LocalHost to the IP address of an interface will make the component initiate connections (or accept in the case of server components) only through that interface. It is recommended to provide an IP address rather than a hostname when setting this property to ensure the desired interface is used.

If the component is connected, the LocalHost property shows the IP address of the interface through which the connection is made in internet dotted format (aaa.bbb.ccc.ddd). In most cases, this is the address of the local host, except for multihomed hosts (machines with more than one IP interface).

NOTE: LocalHost is not persistent. You must always set it in code, and never in the property window.

## Data Type

String

# LocalPort Property ([MQTT](#mqtt-component) Component)

The TCP port in the local host where the component binds.

## Syntax

*C++ Builder Syntax*

```text
__property int LocalPort = { read=FLocalPort, write=FSetLocalPort };
```

## Default Value

0

## Remarks

This property must be set before a connection is attempted. It instructs the component to bind to a specific port (or communication endpoint) in the local machine.

Setting this property to 0 (default) enables the system to choose an open port at random. The chosen port will be returned by the LocalPort property after the connection is established.

LocalPort cannot be changed once a connection is made. Any attempt to set this property when a connection is active will generate an error.

This property is useful when trying to connect to services that require a trusted port on the client side.

## Data Type

Integer

# OutgoingMessageCount Property ([MQTT](#mqtt-component) Component)

The number of records in the OutgoingMessage arrays.

## Syntax

*C++ Builder Syntax*

```text
__property int OutgoingMessageCount = { read=FOutgoingMessageCount };
```

## Default Value

0

## Remarks

This property controls the size of the following arrays:

- [OutgoingMessageContentType](#outgoingmessagecontenttype-property-mqtt-component)
- [OutgoingMessageCorrelationData](#outgoingmessagecorrelationdata-property-mqtt-component)
- [OutgoingMessageDuplicate](#outgoingmessageduplicate-property-mqtt-component)
- [OutgoingMessageMessage](#outgoingmessagemessage-property-mqtt-component)
- [OutgoingMessageMessageExpInterval](#outgoingmessagemessageexpinterval-property-mqtt-component)
- [OutgoingMessagePacketId](#outgoingmessagepacketid-property-mqtt-component)
- [OutgoingMessagePayloadFormatIndicator](#outgoingmessagepayloadformatindicator-property-mqtt-component)
- [OutgoingMessageQoS](#outgoingmessageqos-property-mqtt-component)
- [OutgoingMessageResponseTopic](#outgoingmessageresponsetopic-property-mqtt-component)
- [OutgoingMessageRetained](#outgoingmessageretained-property-mqtt-component)
- [OutgoingMessageState](#outgoingmessagestate-property-mqtt-component)
- [OutgoingMessageSubscriptionIdentifiers](#outgoingmessagesubscriptionidentifiers-property-mqtt-component)
- [OutgoingMessageTopic](#outgoingmessagetopic-property-mqtt-component)
- [OutgoingMessageTopicAlias](#outgoingmessagetopicalias-property-mqtt-component)

The array indices start at *0* and end at *OutgoingMessageCount - 1*.

This property is read-only and not available at design time.

## Data Type

Integer

# OutgoingMessageContentType Property ([MQTT](#mqtt-component) Component)

String describing the content of the message.

## Syntax

*C++ Builder Syntax*

```text
__property String OutgoingMessageContentType[int OutgoingMessageIndex] = { read=FOutgoingMessageContentType };
```

## Default Value

""

## Remarks

String describing the content of the message. Defined by the sending and receiving application.

Valid only for MQTT 5.

The *OutgoingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [OutgoingMessageCount](#outgoingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

String

# OutgoingMessageCorrelationData Property ([MQTT](#mqtt-component) Component)

Used by the sender of the request message to identify which request the response message is for when it is received.

## Syntax

*C++ Builder Syntax*

```text
__property String OutgoingMessageCorrelationData[int OutgoingMessageIndex] = { read=FOutgoingMessageCorrelationData };
```

## Default Value

""

## Remarks

Used by the sender of the request message to identify which request the response message is for when it is received.

Valid only for MQTT 5.

The *OutgoingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [OutgoingMessageCount](#outgoingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

String

# OutgoingMessageDuplicate Property ([MQTT](#mqtt-component) Component)

Whether or not this message's Duplicate flag is set.

## Syntax

*C++ Builder Syntax*

```text
__property bool OutgoingMessageDuplicate[int OutgoingMessageIndex] = { read=FOutgoingMessageDuplicate };
```

## Default Value

false

## Remarks

Whether or not this message's Duplicate flag is set.

The *OutgoingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [OutgoingMessageCount](#outgoingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

Boolean

# OutgoingMessageMessage Property ([MQTT](#mqtt-component) Component)

This message's raw data payload.

## Syntax

*C++ Builder Syntax*

```text
__property String OutgoingMessageMessage[int OutgoingMessageIndex] = { read=FOutgoingMessageMessage };
__property DynamicArray<Byte> OutgoingMessageMessageB[int OutgoingMessageIndex] = { read=FOutgoingMessageMessageB };
```

## Default Value

""

## Remarks

This message's raw data payload.

The *OutgoingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [OutgoingMessageCount](#outgoingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

Byte Array

# OutgoingMessageMessageExpInterval Property ([MQTT](#mqtt-component) Component)

The lifetime of the message in seconds specified by the sender.

## Syntax

*C++ Builder Syntax*

```text
__property int OutgoingMessageMessageExpInterval[int OutgoingMessageIndex] = { read=FOutgoingMessageMessageExpInterval };
```

## Default Value

0

## Remarks

The lifetime of the message in seconds specified by the sender.

For outgoing messages, the value is useful for instructing the server to delete its copies of the message for any subscribers it has not been able to start delivery to.

For incoming messages, the value sent by the server is the lifetime specified by the sender minus the time the message has been waiting in the server.

Valid only for MQTT 5.

The *OutgoingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [OutgoingMessageCount](#outgoingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

Integer

# OutgoingMessagePacketId Property ([MQTT](#mqtt-component) Component)

This message's packet Id.

## Syntax

*C++ Builder Syntax*

```text
__property int OutgoingMessagePacketId[int OutgoingMessageIndex] = { read=FOutgoingMessagePacketId };
```

## Default Value

0

## Remarks

This message's packet Id.

The *OutgoingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [OutgoingMessageCount](#outgoingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

Integer

# OutgoingMessagePayloadFormatIndicator Property ([MQTT](#mqtt-component) Component)

Indicates whether the payload is unspecified bytes or UTF-8 Encoded character data.

## Syntax

*C++ Builder Syntax*

```text
__property int OutgoingMessagePayloadFormatIndicator[int OutgoingMessageIndex] = { read=FOutgoingMessagePayloadFormatIndicator };
```

## Default Value

0

## Remarks

Indicates whether the payload is unspecified bytes or UTF-8 Encoded character data. Possible values are:

|  |  |
| --- | --- |
| Value | Description |
| 0 | Payload is unspecified bytes |
| 1 | Payload is UTF-8 Encoded Character Data |

Valid only for MQTT 5.

The *OutgoingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [OutgoingMessageCount](#outgoingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

Integer

# OutgoingMessageQoS Property ([MQTT](#mqtt-component) Component)

This message's QoS level.

## Syntax

*C++ Builder Syntax*

```text
__property int OutgoingMessageQoS[int OutgoingMessageIndex] = { read=FOutgoingMessageQoS };
```

## Default Value

0

## Remarks

This message's QoS level. Possible values are:

|  |  |
| --- | --- |
| Value | Description |
| 0 | At most once delivery |
| 1 | At least once delivery |
| 2 | Exactly once delivery |

The *OutgoingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [OutgoingMessageCount](#outgoingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

Integer

# OutgoingMessageResponseTopic Property ([MQTT](#mqtt-component) Component)

String used as the topic name for a response message.

## Syntax

*C++ Builder Syntax*

```text
__property String OutgoingMessageResponseTopic[int OutgoingMessageIndex] = { read=FOutgoingMessageResponseTopic };
```

## Default Value

""

## Remarks

String used as the topic name for a response message.

Valid only for MQTT 5.

The *OutgoingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [OutgoingMessageCount](#outgoingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

String

# OutgoingMessageRetained Property ([MQTT](#mqtt-component) Component)

Whether or not this message's Retain flag is set.

## Syntax

*C++ Builder Syntax*

```text
__property bool OutgoingMessageRetained[int OutgoingMessageIndex] = { read=FOutgoingMessageRetained };
```

## Default Value

false

## Remarks

Whether or not this message's Retain flag is set.

The *OutgoingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [OutgoingMessageCount](#outgoingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

Boolean

# OutgoingMessageState Property ([MQTT](#mqtt-component) Component)

This message's current state.

## Syntax

*C++ Builder Syntax*

```text
__property int OutgoingMessageState[int OutgoingMessageIndex] = { read=FOutgoingMessageState };
```

## Default Value

0

## Remarks

This message's current state.

**Possible Outgoing Message States:**

|  |  |
| --- | --- |
| Value | Description |
| 0 | PUBLISH sent, waiting for PUBACK (QoS 1 only) |
| 1 | PUBLISH sent, waiting for PUBREC (QoS 2 only) |
| 2 | PUBREC received, sending PUBREL (QoS 2 only) |
| 3 | PUBREL sent, waiting for PUBCOMP (QoS 2 only) |
| 4 | Final acknowledgment received |

**Possible Incoming Message States:**

|  |  |
| --- | --- |
| Value | Description |
| 5 | PUBLISH received, sending PUBACK (QoS 1 only) |
| 6 | PUBLISH received, sending PUBREC (QoS 2 only) |
| 7 | PUBREC sent, waiting for PUBREL (QoS 2 only) |
| 8 | PUBREL received, sending PUBCOMP (QoS 2 only) |
| 9 | Final acknowledgment sent |

The *OutgoingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [OutgoingMessageCount](#outgoingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

Integer

# OutgoingMessageSubscriptionIdentifiers Property ([MQTT](#mqtt-component) Component)

A comma separated list of any SubscriptionIdentifiers associated with any client subscription(s) that caused this message to be delivered.

## Syntax

*C++ Builder Syntax*

```text
__property String OutgoingMessageSubscriptionIdentifiers[int OutgoingMessageIndex] = { read=FOutgoingMessageSubscriptionIdentifiers };
```

## Default Value

""

## Remarks

A comma separated list of any SubscriptionIdentifiers associated with any client subscription(s) that caused this message to be delivered.

This property is only applicable to incoming messages.

If [SubscriptionIdentifier](#SubscriptionIdentifier) is set when subscribing, it will be included in any messages delivered by the broker for the topics specified in that packet.

See the [Subscribe](#subscribe-method-mqtt-component) method for more details.

Valid only for MQTT 5.

The *OutgoingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [OutgoingMessageCount](#outgoingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

String

# OutgoingMessageTopic Property ([MQTT](#mqtt-component) Component)

This message's topic.

## Syntax

*C++ Builder Syntax*

```text
__property String OutgoingMessageTopic[int OutgoingMessageIndex] = { read=FOutgoingMessageTopic };
```

## Default Value

""

## Remarks

This message's topic.

**MQTT 5 Notes:**

If this value is empty, the [OutgoingMessageTopicAlias](#outgoingmessagetopicalias-property-mqtt-component) property holds the assigned alias for the topic.

If this value is not empty and [OutgoingMessageTopicAlias](#outgoingmessagetopicalias-property-mqtt-component) is non-zero,

The *OutgoingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [OutgoingMessageCount](#outgoingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

String

# OutgoingMessageTopicAlias Property ([MQTT](#mqtt-component) Component)

An integer used to identify the topic instead of the full topic filter in order to reduce the size of the publish packet.

## Syntax

*C++ Builder Syntax*

```text
__property int OutgoingMessageTopicAlias[int OutgoingMessageIndex] = { read=FOutgoingMessageTopicAlias };
```

## Default Value

0

## Remarks

An integer used to identify the topic instead of the full topic filter in order to reduce the size of the publish packet.

If a non-zero topic alias is received, the client should establish a new topic alias mapping or use an existing mapping, depending on whether the [OutgoingMessageTopic](#outgoingmessagetopic-property-mqtt-component) string is empty.

For details on setting topic aliases for outgoing messages, see the [TopicAlias](#TopicAlias) configuration setting.

Valid only for MQTT 5.

The *OutgoingMessageIndex* parameter specifies the index of the item in the array. The size of the array is controlled by the [OutgoingMessageCount](#outgoingmessagecount-property-mqtt-component) property.

This property is read-only and not available at design time.

## Data Type

Integer

# Password Property ([MQTT](#mqtt-component) Component)

A password if authentication is to be used.

## Syntax

*C++ Builder Syntax*

```text
__property String Password = { read=FPassword, write=FSetPassword };
```

## Default Value

""

## Remarks

This property can be set to a password if authentication is to be used.

In MQTT 3.1.1, while a [User](#user-property-mqtt-component) may be specified without a Password, setting a Password without a [User](#user-property-mqtt-component) is not supported; attempting to do so will cause the server to reject the connection attempt.

In MQTT 5, a Password may be set without a [User](#user-property-mqtt-component), allowing the field to be used for credentials other than a password.

This property is not available at design time.

## Data Type

String

# ReadyToSend Property ([MQTT](#mqtt-component) Component)

Indicates whether the component is ready to send data.

## Syntax

*C++ Builder Syntax*

```text
__property bool ReadyToSend = { read=FReadyToSend };
```

## Default Value

false

## Remarks

This property indicates that the underlying TCP/IP subsystem is ready to accept data. This is *True* after connecting to the remote host, and will become *False* if a call to [PublishData](#publishdata-method-mqtt-component) or [PublishMessage](#publishmessage-method-mqtt-component) fails due to a WOULDBLOCK condition.

Once data can be sent again, the [ReadyToSend](#readytosend-event-mqtt-component) event will fire and this property will be *True*.

If a WOULDBLOCK error occurs while sending a message the component will automatically complete the transmission when sending is possible. No action needs to be taken to re-send the message. [ReadyToSend](#readytosend-event-mqtt-component) will fire after the component completes any partially sent messages.

This property is read-only and not available at design time.

## Data Type

Boolean

# RemoteHost Property ([MQTT](#mqtt-component) Component)

The address of the remote host. Domain names are resolved to IP addresses.

## Syntax

*C++ Builder Syntax*

```text
__property String RemoteHost = { read=FRemoteHost, write=FSetRemoteHost };
```

## Default Value

""

## Remarks

This property specifies the IP address (IP number in dotted internet format) or Domain Name of the remote host. It is set before a connection is attempted and cannot be changed once a connection is established.

If this property is set to a Domain Name, a DNS request is initiated, and upon successful termination of the request, this property is set to the corresponding address. If the search is not successful, an error is returned.

If the component is configured to use a *SOCKS* firewall, the value assigned to this property may be preceded with an "*". If this is the case, the host name is passed to the firewall unresolved and the firewall performs the DNS resolution.

By default the component will connect in plaintext. To enable SSL set [SSLEnabled](#sslenabled-property-mqtt-component) to True.

In addition, WebSocket connections are supported. To connect using WebSockets specify a hostname beginning with *ws://* (plaintext) or *wss://* (SSL). For instance, *ws://test.mosquitto.org*.

## Data Type

String

# RemotePort Property ([MQTT](#mqtt-component) Component)

The port of the MQTT server (default is 1883). The default port for SSL is 8883.

## Syntax

*C++ Builder Syntax*

```text
__property int RemotePort = { read=FRemotePort, write=FSetRemotePort };
```

## Default Value

1883

## Remarks

This property specifies a service port on the remote host to connect to.

A valid port number (a value between 1 and 65535) is required for the connection to take place. The property must be set before a connection is attempted and cannot be changed once a connection is established. Any attempt to change this property while connected will fail with an error.

This property is not available at design time.

## Data Type

Integer

# SSLAcceptServerCertEffectiveDate Property ([MQTT](#mqtt-component) Component)

The date on which this certificate becomes valid.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLAcceptServerCertEffectiveDate = { read=FSSLAcceptServerCertEffectiveDate };
```

## Default Value

""

## Remarks

The date on which this certificate becomes valid. Before this date, it is not valid. The date is localized to the system's time zone. The following example illustrates the format of an encoded date:

23-Jan-2000 15:00:00.

This property is read-only.

## Data Type

String

# SSLAcceptServerCertExpirationDate Property ([MQTT](#mqtt-component) Component)

The date on which the certificate expires.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLAcceptServerCertExpirationDate = { read=FSSLAcceptServerCertExpirationDate };
```

## Default Value

""

## Remarks

The date on which the certificate expires. After this date, the certificate will no longer be valid. The date is localized to the system's time zone. The following example illustrates the format of an encoded date:

23-Jan-2001 15:00:00.

This property is read-only.

## Data Type

String

# SSLAcceptServerCertExtendedKeyUsage Property ([MQTT](#mqtt-component) Component)

A comma-delimited list of extended key usage identifiers.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLAcceptServerCertExtendedKeyUsage = { read=FSSLAcceptServerCertExtendedKeyUsage };
```

## Default Value

""

## Remarks

A comma-delimited list of extended key usage identifiers. These are the same as ASN.1 object identifiers (OIDs).

This property is read-only.

## Data Type

String

# SSLAcceptServerCertFingerprint Property ([MQTT](#mqtt-component) Component)

The hex-encoded, 16-byte MD5 fingerprint of the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLAcceptServerCertFingerprint = { read=FSSLAcceptServerCertFingerprint };
```

## Default Value

""

## Remarks

The hex-encoded, 16-byte MD5 fingerprint of the certificate. This property is primarily used for keys which do not have a corresponding X.509 public certificate, such as PEM keys that only contain a private key. It is commonly used for SSH keys.

The following example illustrates the format: *bc:2a:72:af:fe:58:17:43:7a:5f:ba:5a:7c:90:f7:02*

This property is read-only.

## Data Type

String

# SSLAcceptServerCertFingerprintSHA1 Property ([MQTT](#mqtt-component) Component)

The hex-encoded, 20-byte SHA-1 fingerprint of the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLAcceptServerCertFingerprintSHA1 = { read=FSSLAcceptServerCertFingerprintSHA1 };
```

## Default Value

""

## Remarks

The hex-encoded, 20-byte SHA-1 fingerprint of the certificate. This property is primarily used for keys which do not have a corresponding X.509 public certificate, such as PEM keys that only contain a private key. It is commonly used for SSH keys.

The following example illustrates the format: *30:7b:fa:38:65:83:ff:da:b4:4e:07:3f:17:b8:a4:ed:80:be:ff:84*

This property is read-only.

## Data Type

String

# SSLAcceptServerCertFingerprintSHA256 Property ([MQTT](#mqtt-component) Component)

The hex-encoded, 32-byte SHA-256 fingerprint of the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLAcceptServerCertFingerprintSHA256 = { read=FSSLAcceptServerCertFingerprintSHA256 };
```

## Default Value

""

## Remarks

The hex-encoded, 32-byte SHA-256 fingerprint of the certificate. This property is primarily used for keys which do not have a corresponding X.509 public certificate, such as PEM keys that only contain a private key. It is commonly used for SSH keys.

The following example illustrates the format: *6a:80:5c:33:a9:43:ea:b0:96:12:8a:64:96:30:ef:4a:8a:96:86:ce:f4:c7:be:10:24:8e:2b:60:9e:f3:59:53*

This property is read-only.

## Data Type

String

# SSLAcceptServerCertIssuer Property ([MQTT](#mqtt-component) Component)

The issuer of the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLAcceptServerCertIssuer = { read=FSSLAcceptServerCertIssuer };
```

## Default Value

""

## Remarks

The issuer of the certificate. This property contains a string representation of the name of the issuing authority for the certificate.

This property is read-only.

## Data Type

String

# SSLAcceptServerCertPrivateKey Property ([MQTT](#mqtt-component) Component)

The private key of the certificate (if available).

## Syntax

*C++ Builder Syntax*

```text
__property String SSLAcceptServerCertPrivateKey = { read=FSSLAcceptServerCertPrivateKey };
```

## Default Value

""

## Remarks

The private key of the certificate (if available). The key is provided as PEM/Base64-encoded data.

NOTE: The [SSLAcceptServerCertPrivateKey](#sslacceptservercertprivatekey-property-mqtt-component) may be available but not exportable. In this case, [SSLAcceptServerCertPrivateKey](#sslacceptservercertprivatekey-property-mqtt-component) returns an empty string.

This property is read-only.

## Data Type

String

# SSLAcceptServerCertPrivateKeyAvailable Property ([MQTT](#mqtt-component) Component)

Whether a PrivateKey is available for the selected certificate.

## Syntax

*C++ Builder Syntax*

```text
__property bool SSLAcceptServerCertPrivateKeyAvailable = { read=FSSLAcceptServerCertPrivateKeyAvailable };
```

## Default Value

false

## Remarks

Whether a [SSLAcceptServerCertPrivateKey](#sslacceptservercertprivatekey-property-mqtt-component) is available for the selected certificate. If [SSLAcceptServerCertPrivateKeyAvailable](#sslacceptservercertprivatekeyavailable-property-mqtt-component) is True, the certificate may be used for authentication purposes (e.g., server authentication).

This property is read-only.

## Data Type

Boolean

# SSLAcceptServerCertPrivateKeyContainer Property ([MQTT](#mqtt-component) Component)

The name of the PrivateKey container for the certificate (if available).

## Syntax

*C++ Builder Syntax*

```text
__property String SSLAcceptServerCertPrivateKeyContainer = { read=FSSLAcceptServerCertPrivateKeyContainer };
```

## Default Value

""

## Remarks

The name of the [SSLAcceptServerCertPrivateKey](#sslacceptservercertprivatekey-property-mqtt-component) container for the certificate (if available). This functionality is available only on Windows platforms.

This property is read-only.

## Data Type

String

# SSLAcceptServerCertPublicKey Property ([MQTT](#mqtt-component) Component)

The public key of the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLAcceptServerCertPublicKey = { read=FSSLAcceptServerCertPublicKey };
```

## Default Value

""

## Remarks

The public key of the certificate. The key is provided as PEM/Base64-encoded data.

This property is read-only.

## Data Type

String

# SSLAcceptServerCertPublicKeyAlgorithm Property ([MQTT](#mqtt-component) Component)

The textual description of the certificate's public key algorithm.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLAcceptServerCertPublicKeyAlgorithm = { read=FSSLAcceptServerCertPublicKeyAlgorithm };
```

## Default Value

""

## Remarks

The textual description of the certificate's public key algorithm. The property contains either the name of the algorithm (e.g., "RSA" or "RSA_DH") or an object identifier (OID) string representing the algorithm.

This property is read-only.

## Data Type

String

# SSLAcceptServerCertPublicKeyLength Property ([MQTT](#mqtt-component) Component)

The length of the certificate's public key (in bits).

## Syntax

*C++ Builder Syntax*

```text
__property int SSLAcceptServerCertPublicKeyLength = { read=FSSLAcceptServerCertPublicKeyLength };
```

## Default Value

0

## Remarks

The length of the certificate's public key (in bits). Common values are 512, 1024, and 2048.

This property is read-only.

## Data Type

Integer

# SSLAcceptServerCertSerialNumber Property ([MQTT](#mqtt-component) Component)

The serial number of the certificate encoded as a string.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLAcceptServerCertSerialNumber = { read=FSSLAcceptServerCertSerialNumber };
```

## Default Value

""

## Remarks

The serial number of the certificate encoded as a string. The number is encoded as a series of hexadecimal digits, with each pair representing a byte of the serial number.

This property is read-only.

## Data Type

String

# SSLAcceptServerCertSignatureAlgorithm Property ([MQTT](#mqtt-component) Component)

The text description of the certificate's signature algorithm.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLAcceptServerCertSignatureAlgorithm = { read=FSSLAcceptServerCertSignatureAlgorithm };
```

## Default Value

""

## Remarks

The text description of the certificate's signature algorithm. The property contains either the name of the algorithm (e.g., "RSA" or "RSA_MD5RSA") or an object identifier (OID) string representing the algorithm.

This property is read-only.

## Data Type

String

# SSLAcceptServerCertStore Property ([MQTT](#mqtt-component) Component)

The name of the certificate store for the client certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLAcceptServerCertStore = { read=FSSLAcceptServerCertStore, write=FSetSSLAcceptServerCertStore };
__property DynamicArray<Byte> SSLAcceptServerCertStoreB = { read=FSSLAcceptServerCertStoreB, write=FSetSSLAcceptServerCertStoreB };
```

## Default Value

"MY"

## Remarks

The name of the certificate store for the client certificate.

The [SSLAcceptServerCertStoreType](#sslacceptservercertstoretype-property-mqtt-component) property denotes the type of the certificate store specified by [SSLAcceptServerCertStore](#sslacceptservercertstore-property-mqtt-component). If the store is password-protected, specify the password in [SSLAcceptServerCertStorePassword](#sslacceptservercertstorepassword-property-mqtt-component).

[SSLAcceptServerCertStore](#sslacceptservercertstore-property-mqtt-component) is used in conjunction with the [SSLAcceptServerCertSubject](#sslacceptservercertsubject-property-mqtt-component) property to specify client certificates. If [SSLAcceptServerCertStore](#sslacceptservercertstore-property-mqtt-component) has a value, and [SSLAcceptServerCertSubject](#sslacceptservercertsubject-property-mqtt-component) or [SSLAcceptServerCertEncoded](#sslacceptservercertencoded-property-mqtt-component) is set, a search for a certificate is initiated. Please see the [SSLAcceptServerCertSubject](#sslacceptservercertsubject-property-mqtt-component) property for details.

 Designations of certificate stores are platform dependent.

The following designations are the most common User and Machine certificate stores in Windows:

|  |  |
| --- | --- |
| MY | A certificate store holding personal certificates with their associated private keys. |
| CA | Certifying authority certificates. |
| ROOT | Root certificates. |

When the certificate store type is *cstPFXFile*, this property must be set to the name of the file. When the type is *cstPFXBlob*, the property must be set to the binary contents of a PFX file (i.e., PKCS#12 certificate store).

## Data Type

Byte Array

# SSLAcceptServerCertStorePassword Property ([MQTT](#mqtt-component) Component)

If the type of certificate store requires a password, this property is used to specify the password needed to open the certificate store.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLAcceptServerCertStorePassword = { read=FSSLAcceptServerCertStorePassword, write=FSetSSLAcceptServerCertStorePassword };
```

## Default Value

""

## Remarks

If the type of certificate store requires a password, this property is used to specify the password needed to open the certificate store.

## Data Type

String

# SSLAcceptServerCertStoreType Property ([MQTT](#mqtt-component) Component)

The type of certificate store for this certificate.

## Syntax

*C++ Builder Syntax*

```text
__property TiotMQTTSSLAcceptServerCertStoreTypes SSLAcceptServerCertStoreType = { read=FSSLAcceptServerCertStoreType, write=FSetSSLAcceptServerCertStoreType };
enum TiotMQTTSSLAcceptServerCertStoreTypes {
  cstUser=0,
  cstMachine=1,
  cstPFXFile=2,
  cstPFXBlob=3,
  cstJKSFile=4,
  cstJKSBlob=5,
  cstPEMKeyFile=6,
  cstPEMKeyBlob=7,
  cstPublicKeyFile=8,
  cstPublicKeyBlob=9,
  cstSSHPublicKeyBlob=10,
  cstP7BFile=11,
  cstP7BBlob=12,
  cstSSHPublicKeyFile=13,
  cstPPKFile=14,
  cstPPKBlob=15,
  cstXMLFile=16,
  cstXMLBlob=17,
  cstJWKFile=18,
  cstJWKBlob=19,
  cstSecurityKey=20,
  cstBCFKSFile=21,
  cstBCFKSBlob=22,
  cstPKCS11=23,
  cstAuto=99
};
```

## Default Value

cstUser

## Remarks

The type of certificate store for this certificate.

 The component supports both public and private keys in a variety of formats. When the *cstAuto* value is used, the component will automatically determine the type. This property can take one of the following values:

```csharp
sftp.SSHCert = new Certificate(CertStoreTypes.cstPKCS11,
                               @"C:\Program Files\OpenSC Project\OpenSC\pkcs11\opensc-pkcs11.dll",
                               "123456", // PIN
                               "CN=cert_subject");
sftp.SSHUser = "test";
sftp.SSHLogon("myhost", 22);
```

```csharp
certmgr.CertStoreType = CertStoreTypes.cstPKCS11;
certmgr.OnCertList += (s, e) => {
  secKeyBlob = e.CertEncoded;
};
certmgr.CertStore = @"C:\Program Files\OpenSC Project\OpenSC\pkcs11\opensc-pkcs11.dll";
certmgr.CertStorePassword = "123456"; // PIN
certmgr.ListStoreCertificates();

sftp.SSHCert = new Certificate(CertStoreTypes.cstPKCS11, secKeyBlob, "123456", "*");
sftp.SSHUser = "test";
sftp.SSHLogon("myhost", 22);
```

|  |  |
| --- | --- |
| 0 (cstUser - default) | For Windows, this specifies that the certificate store is a certificate store owned by the current user. NOTE: This store type is not available in Java. |
| 1 (cstMachine) | For Windows, this specifies that the certificate store is a machine store. NOTE: This store type is not available in Java. |
| 2 (cstPFXFile) | The certificate store is the name of a PFX (PKCS#12) file containing certificates. |
| 3 (cstPFXBlob) | The certificate store is a string (binary or Base64-encoded) representing a certificate store in PFX (PKCS#12) format. |
| 4 (cstJKSFile) | The certificate store is the name of a Java Key Store (JKS) file containing certificates. NOTE: This store type is only available in Java. |
| 5 (cstJKSBlob) | The certificate store is a string (binary or Base64-encoded) representing a certificate store in Java Key Store (JKS) format. NOTE: This store type is only available in Java. |
| 6 (cstPEMKeyFile) | The certificate store is the name of a PEM-encoded file that contains a private key and an optional certificate. |
| 7 (cstPEMKeyBlob) | The certificate store is a string (binary or Base64-encoded) that contains a private key and an optional certificate. |
| 8 (cstPublicKeyFile) | The certificate store is the name of a file that contains a PEM- or DER-encoded public key certificate. |
| 9 (cstPublicKeyBlob) | The certificate store is a string (binary or Base64-encoded) that contains a PEM- or DER-encoded public key certificate. |
| 10 (cstSSHPublicKeyBlob) | The certificate store is a string (binary or Base64-encoded) that contains an SSH-style public key. |
| 11 (cstP7BFile) | The certificate store is the name of a PKCS#7 file containing certificates. |
| 12 (cstP7BBlob) | The certificate store is a string (binary) representing a certificate store in PKCS#7 format. |
| 13 (cstSSHPublicKeyFile) | The certificate store is the name of a file that contains an SSH-style public key. |
| 14 (cstPPKFile) | The certificate store is the name of a file that contains a PPK (PuTTY Private Key). |
| 15 (cstPPKBlob) | The certificate store is a string (binary) that contains a PPK (PuTTY Private Key). |
| 16 (cstXMLFile) | The certificate store is the name of a file that contains a certificate in XML format. |
| 17 (cstXMLBlob) | The certificate store is a string that contains a certificate in XML format. |
| 18 (cstJWKFile) | The certificate store is the name of a file that contains a JWK (JSON Web Key). |
| 19 (cstJWKBlob) | The certificate store is a string that contains a JWK (JSON Web Key). |
| 21 (cstBCFKSFile) | The certificate store is the name of a file that contains a BCFKS (Bouncy Castle FIPS Key Store). NOTE: This store type is only available in Java and .NET. |
| 22 (cstBCFKSBlob) | The certificate store is a string (binary or Base64-encoded) representing a certificate store in BCFKS (Bouncy Castle FIPS Key Store) format. NOTE: This store type is only available in Java and .NET. |
| 23 (cstPKCS11) | The certificate is present on a physical security key accessible via a PKCS#11 interface. To use a security key, create a new [Certificate](#Type_Certificate) object and pass cstPKCS11 as the [SSLAcceptServerCertStoreType](#sslacceptservercertstoretype-property-mqtt-component), the full path of the PKCS#11 DLL as the [SSLAcceptServerCertStore](#sslacceptservercertstore-property-mqtt-component), and the PIN as the [SSLAcceptServerCertStorePassword](#sslacceptservercertstorepassword-property-mqtt-component). Code Example. SSH Authentication with Security Key (without CertMgr): Alternatively, collect the necessary data using the [CertMgr](#CertMgr) component by calling the [ListStoreCertificates](#CertMgr_m_ListStoreCertificates) method after setting the corresponding properties accordingly. The certificate information returned in the [CertList](#CertMgr_e_CertList) event's CertEncoded parameter may be saved for later use. When using a certificate obtained with this approach, pass the previously saved security key information as the [SSLAcceptServerCertStore](#sslacceptservercertstore-property-mqtt-component) and set [SSLAcceptServerCertStorePassword](#sslacceptservercertstorepassword-property-mqtt-component) to the PIN. Code Example. SSH Authentication with Security Key (with CertMgr): |
| 99 (cstAuto) | The store type is automatically detected from the input data. This setting may be used with both public and private keys and can detect any of the supported formats automatically. |

## Data Type

Integer

# SSLAcceptServerCertSubjectAltNames Property ([MQTT](#mqtt-component) Component)

Comma-separated lists of alternative subject names for the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLAcceptServerCertSubjectAltNames = { read=FSSLAcceptServerCertSubjectAltNames };
```

## Default Value

""

## Remarks

Comma-separated lists of alternative subject names for the certificate.

This property is read-only.

## Data Type

String

# SSLAcceptServerCertThumbprintMD5 Property ([MQTT](#mqtt-component) Component)

The MD5 hash of the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLAcceptServerCertThumbprintMD5 = { read=FSSLAcceptServerCertThumbprintMD5 };
```

## Default Value

""

## Remarks

The MD5 hash of the certificate. It is primarily used for X.509 certificates. If the hash does not already exist, it is automatically computed.

This property is read-only.

## Data Type

String

# SSLAcceptServerCertThumbprintSHA1 Property ([MQTT](#mqtt-component) Component)

The SHA-1 hash of the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLAcceptServerCertThumbprintSHA1 = { read=FSSLAcceptServerCertThumbprintSHA1 };
```

## Default Value

""

## Remarks

The SHA-1 hash of the certificate. It is primarily used for X.509 certificates. If the hash does not already exist, it is automatically computed.

This property is read-only.

## Data Type

String

# SSLAcceptServerCertThumbprintSHA256 Property ([MQTT](#mqtt-component) Component)

The SHA-256 hash of the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLAcceptServerCertThumbprintSHA256 = { read=FSSLAcceptServerCertThumbprintSHA256 };
```

## Default Value

""

## Remarks

The SHA-256 hash of the certificate. It is primarily used for X.509 certificates. If the hash does not already exist, it is automatically computed.

This property is read-only.

## Data Type

String

# SSLAcceptServerCertUsage Property ([MQTT](#mqtt-component) Component)

The text description of UsageFlags .

## Syntax

*C++ Builder Syntax*

```text
__property String SSLAcceptServerCertUsage = { read=FSSLAcceptServerCertUsage };
```

## Default Value

""

## Remarks

The text description of [SSLAcceptServerCertUsageFlags](#sslacceptservercertusageflags-property-mqtt-component).

This value will be one or more of the following strings and will be separated by commas:

- Digital Signature
- Non-Repudiation
- Key Encipherment
- Data Encipherment
- Key Agreement
- Certificate Signing
- CRL Signing
- Encipher Only

If the provider is OpenSSL, the value is a comma-separated list of X.509 certificate extension names.

This property is read-only.

## Data Type

String

# SSLAcceptServerCertUsageFlags Property ([MQTT](#mqtt-component) Component)

The flags that show intended use for the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property int SSLAcceptServerCertUsageFlags = { read=FSSLAcceptServerCertUsageFlags };
```

## Default Value

0

## Remarks

The flags that show intended use for the certificate. The value of [SSLAcceptServerCertUsageFlags](#sslacceptservercertusageflags-property-mqtt-component) is a combination of the following flags:

|  |  |
| --- | --- |
| 0x80 | Digital Signature |
| 0x40 | Non-Repudiation |
| 0x20 | Key Encipherment |
| 0x10 | Data Encipherment |
| 0x08 | Key Agreement |
| 0x04 | Certificate Signing |
| 0x02 | CRL Signing |
| 0x01 | Encipher Only |

Please see the [SSLAcceptServerCertUsage](#sslacceptservercertusage-property-mqtt-component) property for a text representation of [SSLAcceptServerCertUsageFlags](#sslacceptservercertusageflags-property-mqtt-component).

This functionality currently is not available when the provider is OpenSSL.

This property is read-only.

## Data Type

Integer

# SSLAcceptServerCertVersion Property ([MQTT](#mqtt-component) Component)

The certificate's version number.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLAcceptServerCertVersion = { read=FSSLAcceptServerCertVersion };
```

## Default Value

""

## Remarks

The certificate's version number. The possible values are the strings "V1", "V2", and "V3".

This property is read-only.

## Data Type

String

# SSLAcceptServerCertSubject Property ([MQTT](#mqtt-component) Component)

The subject of the certificate used for client authentication.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLAcceptServerCertSubject = { read=FSSLAcceptServerCertSubject, write=FSetSSLAcceptServerCertSubject };
```

## Default Value

""

## Remarks

The subject of the certificate used for client authentication.

This property must be set after all other certificate properties are set. When this property is set, a search is performed in the current certificate store to locate a certificate with a matching subject.

If a matching certificate is found, the property is set to the full subject of the matching certificate.

If an exact match is not found, the store is searched for subjects containing the value of the property.

If a match is still not found, the property is set to an empty string, and no certificate is selected.

The special value "*" picks a random certificate in the certificate store.

The certificate subject is a comma-separated list of distinguished name fields and values. For instance, "CN=www.server.com, OU=test, C=US, E=example@email.com". Common fields and their meanings are as follows:

| Field | Meaning |
| --- | --- |
| CN | Common Name. This is commonly a hostname like www.server.com. |
| O | Organization |
| OU | Organizational Unit |
| L | Locality |
| S | State |
| C | Country |
| E | Email Address |

If a field value contains a comma, it must be quoted.

## Data Type

String

# SSLAcceptServerCertEncoded Property ([MQTT](#mqtt-component) Component)

The certificate (PEM/Base64 encoded).

## Syntax

*C++ Builder Syntax*

```text
__property String SSLAcceptServerCertEncoded = { read=FSSLAcceptServerCertEncoded, write=FSetSSLAcceptServerCertEncoded };
__property DynamicArray<Byte> SSLAcceptServerCertEncodedB = { read=FSSLAcceptServerCertEncodedB, write=FSetSSLAcceptServerCertEncodedB };
```

## Default Value

""

## Remarks

The certificate (PEM/Base64 encoded). This property is used to assign a specific certificate. The [SSLAcceptServerCertStore](#sslacceptservercertstore-property-mqtt-component) and [SSLAcceptServerCertSubject](#sslacceptservercertsubject-property-mqtt-component) properties also may be used to specify a certificate.

When [SSLAcceptServerCertEncoded](#sslacceptservercertencoded-property-mqtt-component) is set, a search is initiated in the current [SSLAcceptServerCertStore](#sslacceptservercertstore-property-mqtt-component) for the private key of the certificate. If the key is found, [SSLAcceptServerCertSubject](#sslacceptservercertsubject-property-mqtt-component) is updated to reflect the full subject of the selected certificate; otherwise, [SSLAcceptServerCertSubject](#sslacceptservercertsubject-property-mqtt-component) is set to an empty string.

This property is not available at design time.

## Data Type

Byte Array

# SSLCertEffectiveDate Property ([MQTT](#mqtt-component) Component)

The date on which this certificate becomes valid.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLCertEffectiveDate = { read=FSSLCertEffectiveDate };
```

## Default Value

""

## Remarks

The date on which this certificate becomes valid. Before this date, it is not valid. The date is localized to the system's time zone. The following example illustrates the format of an encoded date:

23-Jan-2000 15:00:00.

This property is read-only.

## Data Type

String

# SSLCertExpirationDate Property ([MQTT](#mqtt-component) Component)

The date on which the certificate expires.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLCertExpirationDate = { read=FSSLCertExpirationDate };
```

## Default Value

""

## Remarks

The date on which the certificate expires. After this date, the certificate will no longer be valid. The date is localized to the system's time zone. The following example illustrates the format of an encoded date:

23-Jan-2001 15:00:00.

This property is read-only.

## Data Type

String

# SSLCertExtendedKeyUsage Property ([MQTT](#mqtt-component) Component)

A comma-delimited list of extended key usage identifiers.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLCertExtendedKeyUsage = { read=FSSLCertExtendedKeyUsage };
```

## Default Value

""

## Remarks

A comma-delimited list of extended key usage identifiers. These are the same as ASN.1 object identifiers (OIDs).

This property is read-only.

## Data Type

String

# SSLCertFingerprint Property ([MQTT](#mqtt-component) Component)

The hex-encoded, 16-byte MD5 fingerprint of the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLCertFingerprint = { read=FSSLCertFingerprint };
```

## Default Value

""

## Remarks

The hex-encoded, 16-byte MD5 fingerprint of the certificate. This property is primarily used for keys which do not have a corresponding X.509 public certificate, such as PEM keys that only contain a private key. It is commonly used for SSH keys.

The following example illustrates the format: *bc:2a:72:af:fe:58:17:43:7a:5f:ba:5a:7c:90:f7:02*

This property is read-only.

## Data Type

String

# SSLCertFingerprintSHA1 Property ([MQTT](#mqtt-component) Component)

The hex-encoded, 20-byte SHA-1 fingerprint of the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLCertFingerprintSHA1 = { read=FSSLCertFingerprintSHA1 };
```

## Default Value

""

## Remarks

The hex-encoded, 20-byte SHA-1 fingerprint of the certificate. This property is primarily used for keys which do not have a corresponding X.509 public certificate, such as PEM keys that only contain a private key. It is commonly used for SSH keys.

The following example illustrates the format: *30:7b:fa:38:65:83:ff:da:b4:4e:07:3f:17:b8:a4:ed:80:be:ff:84*

This property is read-only.

## Data Type

String

# SSLCertFingerprintSHA256 Property ([MQTT](#mqtt-component) Component)

The hex-encoded, 32-byte SHA-256 fingerprint of the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLCertFingerprintSHA256 = { read=FSSLCertFingerprintSHA256 };
```

## Default Value

""

## Remarks

The hex-encoded, 32-byte SHA-256 fingerprint of the certificate. This property is primarily used for keys which do not have a corresponding X.509 public certificate, such as PEM keys that only contain a private key. It is commonly used for SSH keys.

The following example illustrates the format: *6a:80:5c:33:a9:43:ea:b0:96:12:8a:64:96:30:ef:4a:8a:96:86:ce:f4:c7:be:10:24:8e:2b:60:9e:f3:59:53*

This property is read-only.

## Data Type

String

# SSLCertIssuer Property ([MQTT](#mqtt-component) Component)

The issuer of the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLCertIssuer = { read=FSSLCertIssuer };
```

## Default Value

""

## Remarks

The issuer of the certificate. This property contains a string representation of the name of the issuing authority for the certificate.

This property is read-only.

## Data Type

String

# SSLCertPrivateKey Property ([MQTT](#mqtt-component) Component)

The private key of the certificate (if available).

## Syntax

*C++ Builder Syntax*

```text
__property String SSLCertPrivateKey = { read=FSSLCertPrivateKey };
```

## Default Value

""

## Remarks

The private key of the certificate (if available). The key is provided as PEM/Base64-encoded data.

NOTE: The [SSLCertPrivateKey](#sslcertprivatekey-property-mqtt-component) may be available but not exportable. In this case, [SSLCertPrivateKey](#sslcertprivatekey-property-mqtt-component) returns an empty string.

This property is read-only.

## Data Type

String

# SSLCertPrivateKeyAvailable Property ([MQTT](#mqtt-component) Component)

Whether a PrivateKey is available for the selected certificate.

## Syntax

*C++ Builder Syntax*

```text
__property bool SSLCertPrivateKeyAvailable = { read=FSSLCertPrivateKeyAvailable };
```

## Default Value

false

## Remarks

Whether a [SSLCertPrivateKey](#sslcertprivatekey-property-mqtt-component) is available for the selected certificate. If [SSLCertPrivateKeyAvailable](#sslcertprivatekeyavailable-property-mqtt-component) is True, the certificate may be used for authentication purposes (e.g., server authentication).

This property is read-only.

## Data Type

Boolean

# SSLCertPrivateKeyContainer Property ([MQTT](#mqtt-component) Component)

The name of the PrivateKey container for the certificate (if available).

## Syntax

*C++ Builder Syntax*

```text
__property String SSLCertPrivateKeyContainer = { read=FSSLCertPrivateKeyContainer };
```

## Default Value

""

## Remarks

The name of the [SSLCertPrivateKey](#sslcertprivatekey-property-mqtt-component) container for the certificate (if available). This functionality is available only on Windows platforms.

This property is read-only.

## Data Type

String

# SSLCertPublicKey Property ([MQTT](#mqtt-component) Component)

The public key of the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLCertPublicKey = { read=FSSLCertPublicKey };
```

## Default Value

""

## Remarks

The public key of the certificate. The key is provided as PEM/Base64-encoded data.

This property is read-only.

## Data Type

String

# SSLCertPublicKeyAlgorithm Property ([MQTT](#mqtt-component) Component)

The textual description of the certificate's public key algorithm.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLCertPublicKeyAlgorithm = { read=FSSLCertPublicKeyAlgorithm };
```

## Default Value

""

## Remarks

The textual description of the certificate's public key algorithm. The property contains either the name of the algorithm (e.g., "RSA" or "RSA_DH") or an object identifier (OID) string representing the algorithm.

This property is read-only.

## Data Type

String

# SSLCertPublicKeyLength Property ([MQTT](#mqtt-component) Component)

The length of the certificate's public key (in bits).

## Syntax

*C++ Builder Syntax*

```text
__property int SSLCertPublicKeyLength = { read=FSSLCertPublicKeyLength };
```

## Default Value

0

## Remarks

The length of the certificate's public key (in bits). Common values are 512, 1024, and 2048.

This property is read-only.

## Data Type

Integer

# SSLCertSerialNumber Property ([MQTT](#mqtt-component) Component)

The serial number of the certificate encoded as a string.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLCertSerialNumber = { read=FSSLCertSerialNumber };
```

## Default Value

""

## Remarks

The serial number of the certificate encoded as a string. The number is encoded as a series of hexadecimal digits, with each pair representing a byte of the serial number.

This property is read-only.

## Data Type

String

# SSLCertSignatureAlgorithm Property ([MQTT](#mqtt-component) Component)

The text description of the certificate's signature algorithm.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLCertSignatureAlgorithm = { read=FSSLCertSignatureAlgorithm };
```

## Default Value

""

## Remarks

The text description of the certificate's signature algorithm. The property contains either the name of the algorithm (e.g., "RSA" or "RSA_MD5RSA") or an object identifier (OID) string representing the algorithm.

This property is read-only.

## Data Type

String

# SSLCertStore Property ([MQTT](#mqtt-component) Component)

The name of the certificate store for the client certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLCertStore = { read=FSSLCertStore, write=FSetSSLCertStore };
__property DynamicArray<Byte> SSLCertStoreB = { read=FSSLCertStoreB, write=FSetSSLCertStoreB };
```

## Default Value

"MY"

## Remarks

The name of the certificate store for the client certificate.

The [SSLCertStoreType](#sslcertstoretype-property-mqtt-component) property denotes the type of the certificate store specified by [SSLCertStore](#sslcertstore-property-mqtt-component). If the store is password-protected, specify the password in [SSLCertStorePassword](#sslcertstorepassword-property-mqtt-component).

[SSLCertStore](#sslcertstore-property-mqtt-component) is used in conjunction with the [SSLCertSubject](#sslcertsubject-property-mqtt-component) property to specify client certificates. If [SSLCertStore](#sslcertstore-property-mqtt-component) has a value, and [SSLCertSubject](#sslcertsubject-property-mqtt-component) or [SSLCertEncoded](#sslcertencoded-property-mqtt-component) is set, a search for a certificate is initiated. Please see the [SSLCertSubject](#sslcertsubject-property-mqtt-component) property for details.

 Designations of certificate stores are platform dependent.

The following designations are the most common User and Machine certificate stores in Windows:

|  |  |
| --- | --- |
| MY | A certificate store holding personal certificates with their associated private keys. |
| CA | Certifying authority certificates. |
| ROOT | Root certificates. |

When the certificate store type is *cstPFXFile*, this property must be set to the name of the file. When the type is *cstPFXBlob*, the property must be set to the binary contents of a PFX file (i.e., PKCS#12 certificate store).

## Data Type

Byte Array

# SSLCertStorePassword Property ([MQTT](#mqtt-component) Component)

If the type of certificate store requires a password, this property is used to specify the password needed to open the certificate store.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLCertStorePassword = { read=FSSLCertStorePassword, write=FSetSSLCertStorePassword };
```

## Default Value

""

## Remarks

If the type of certificate store requires a password, this property is used to specify the password needed to open the certificate store.

## Data Type

String

# SSLCertStoreType Property ([MQTT](#mqtt-component) Component)

The type of certificate store for this certificate.

## Syntax

*C++ Builder Syntax*

```text
__property TiotMQTTSSLCertStoreTypes SSLCertStoreType = { read=FSSLCertStoreType, write=FSetSSLCertStoreType };
enum TiotMQTTSSLCertStoreTypes {
  cstUser=0,
  cstMachine=1,
  cstPFXFile=2,
  cstPFXBlob=3,
  cstJKSFile=4,
  cstJKSBlob=5,
  cstPEMKeyFile=6,
  cstPEMKeyBlob=7,
  cstPublicKeyFile=8,
  cstPublicKeyBlob=9,
  cstSSHPublicKeyBlob=10,
  cstP7BFile=11,
  cstP7BBlob=12,
  cstSSHPublicKeyFile=13,
  cstPPKFile=14,
  cstPPKBlob=15,
  cstXMLFile=16,
  cstXMLBlob=17,
  cstJWKFile=18,
  cstJWKBlob=19,
  cstSecurityKey=20,
  cstBCFKSFile=21,
  cstBCFKSBlob=22,
  cstPKCS11=23,
  cstAuto=99
};
```

## Default Value

cstUser

## Remarks

The type of certificate store for this certificate.

 The component supports both public and private keys in a variety of formats. When the *cstAuto* value is used, the component will automatically determine the type. This property can take one of the following values:

```csharp
sftp.SSHCert = new Certificate(CertStoreTypes.cstPKCS11,
                               @"C:\Program Files\OpenSC Project\OpenSC\pkcs11\opensc-pkcs11.dll",
                               "123456", // PIN
                               "CN=cert_subject");
sftp.SSHUser = "test";
sftp.SSHLogon("myhost", 22);
```

```csharp
certmgr.CertStoreType = CertStoreTypes.cstPKCS11;
certmgr.OnCertList += (s, e) => {
  secKeyBlob = e.CertEncoded;
};
certmgr.CertStore = @"C:\Program Files\OpenSC Project\OpenSC\pkcs11\opensc-pkcs11.dll";
certmgr.CertStorePassword = "123456"; // PIN
certmgr.ListStoreCertificates();

sftp.SSHCert = new Certificate(CertStoreTypes.cstPKCS11, secKeyBlob, "123456", "*");
sftp.SSHUser = "test";
sftp.SSHLogon("myhost", 22);
```

|  |  |
| --- | --- |
| 0 (cstUser - default) | For Windows, this specifies that the certificate store is a certificate store owned by the current user. NOTE: This store type is not available in Java. |
| 1 (cstMachine) | For Windows, this specifies that the certificate store is a machine store. NOTE: This store type is not available in Java. |
| 2 (cstPFXFile) | The certificate store is the name of a PFX (PKCS#12) file containing certificates. |
| 3 (cstPFXBlob) | The certificate store is a string (binary or Base64-encoded) representing a certificate store in PFX (PKCS#12) format. |
| 4 (cstJKSFile) | The certificate store is the name of a Java Key Store (JKS) file containing certificates. NOTE: This store type is only available in Java. |
| 5 (cstJKSBlob) | The certificate store is a string (binary or Base64-encoded) representing a certificate store in Java Key Store (JKS) format. NOTE: This store type is only available in Java. |
| 6 (cstPEMKeyFile) | The certificate store is the name of a PEM-encoded file that contains a private key and an optional certificate. |
| 7 (cstPEMKeyBlob) | The certificate store is a string (binary or Base64-encoded) that contains a private key and an optional certificate. |
| 8 (cstPublicKeyFile) | The certificate store is the name of a file that contains a PEM- or DER-encoded public key certificate. |
| 9 (cstPublicKeyBlob) | The certificate store is a string (binary or Base64-encoded) that contains a PEM- or DER-encoded public key certificate. |
| 10 (cstSSHPublicKeyBlob) | The certificate store is a string (binary or Base64-encoded) that contains an SSH-style public key. |
| 11 (cstP7BFile) | The certificate store is the name of a PKCS#7 file containing certificates. |
| 12 (cstP7BBlob) | The certificate store is a string (binary) representing a certificate store in PKCS#7 format. |
| 13 (cstSSHPublicKeyFile) | The certificate store is the name of a file that contains an SSH-style public key. |
| 14 (cstPPKFile) | The certificate store is the name of a file that contains a PPK (PuTTY Private Key). |
| 15 (cstPPKBlob) | The certificate store is a string (binary) that contains a PPK (PuTTY Private Key). |
| 16 (cstXMLFile) | The certificate store is the name of a file that contains a certificate in XML format. |
| 17 (cstXMLBlob) | The certificate store is a string that contains a certificate in XML format. |
| 18 (cstJWKFile) | The certificate store is the name of a file that contains a JWK (JSON Web Key). |
| 19 (cstJWKBlob) | The certificate store is a string that contains a JWK (JSON Web Key). |
| 21 (cstBCFKSFile) | The certificate store is the name of a file that contains a BCFKS (Bouncy Castle FIPS Key Store). NOTE: This store type is only available in Java and .NET. |
| 22 (cstBCFKSBlob) | The certificate store is a string (binary or Base64-encoded) representing a certificate store in BCFKS (Bouncy Castle FIPS Key Store) format. NOTE: This store type is only available in Java and .NET. |
| 23 (cstPKCS11) | The certificate is present on a physical security key accessible via a PKCS#11 interface. To use a security key, create a new [Certificate](#Type_Certificate) object and pass cstPKCS11 as the [SSLCertStoreType](#sslcertstoretype-property-mqtt-component), the full path of the PKCS#11 DLL as the [SSLCertStore](#sslcertstore-property-mqtt-component), and the PIN as the [SSLCertStorePassword](#sslcertstorepassword-property-mqtt-component). Code Example. SSH Authentication with Security Key (without CertMgr): Alternatively, collect the necessary data using the [CertMgr](#CertMgr) component by calling the [ListStoreCertificates](#CertMgr_m_ListStoreCertificates) method after setting the corresponding properties accordingly. The certificate information returned in the [CertList](#CertMgr_e_CertList) event's CertEncoded parameter may be saved for later use. When using a certificate obtained with this approach, pass the previously saved security key information as the [SSLCertStore](#sslcertstore-property-mqtt-component) and set [SSLCertStorePassword](#sslcertstorepassword-property-mqtt-component) to the PIN. Code Example. SSH Authentication with Security Key (with CertMgr): |
| 99 (cstAuto) | The store type is automatically detected from the input data. This setting may be used with both public and private keys and can detect any of the supported formats automatically. |

## Data Type

Integer

# SSLCertSubjectAltNames Property ([MQTT](#mqtt-component) Component)

Comma-separated lists of alternative subject names for the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLCertSubjectAltNames = { read=FSSLCertSubjectAltNames };
```

## Default Value

""

## Remarks

Comma-separated lists of alternative subject names for the certificate.

This property is read-only.

## Data Type

String

# SSLCertThumbprintMD5 Property ([MQTT](#mqtt-component) Component)

The MD5 hash of the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLCertThumbprintMD5 = { read=FSSLCertThumbprintMD5 };
```

## Default Value

""

## Remarks

The MD5 hash of the certificate. It is primarily used for X.509 certificates. If the hash does not already exist, it is automatically computed.

This property is read-only.

## Data Type

String

# SSLCertThumbprintSHA1 Property ([MQTT](#mqtt-component) Component)

The SHA-1 hash of the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLCertThumbprintSHA1 = { read=FSSLCertThumbprintSHA1 };
```

## Default Value

""

## Remarks

The SHA-1 hash of the certificate. It is primarily used for X.509 certificates. If the hash does not already exist, it is automatically computed.

This property is read-only.

## Data Type

String

# SSLCertThumbprintSHA256 Property ([MQTT](#mqtt-component) Component)

The SHA-256 hash of the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLCertThumbprintSHA256 = { read=FSSLCertThumbprintSHA256 };
```

## Default Value

""

## Remarks

The SHA-256 hash of the certificate. It is primarily used for X.509 certificates. If the hash does not already exist, it is automatically computed.

This property is read-only.

## Data Type

String

# SSLCertUsage Property ([MQTT](#mqtt-component) Component)

The text description of UsageFlags .

## Syntax

*C++ Builder Syntax*

```text
__property String SSLCertUsage = { read=FSSLCertUsage };
```

## Default Value

""

## Remarks

The text description of [SSLCertUsageFlags](#sslcertusageflags-property-mqtt-component).

This value will be one or more of the following strings and will be separated by commas:

- Digital Signature
- Non-Repudiation
- Key Encipherment
- Data Encipherment
- Key Agreement
- Certificate Signing
- CRL Signing
- Encipher Only

If the provider is OpenSSL, the value is a comma-separated list of X.509 certificate extension names.

This property is read-only.

## Data Type

String

# SSLCertUsageFlags Property ([MQTT](#mqtt-component) Component)

The flags that show intended use for the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property int SSLCertUsageFlags = { read=FSSLCertUsageFlags };
```

## Default Value

0

## Remarks

The flags that show intended use for the certificate. The value of [SSLCertUsageFlags](#sslcertusageflags-property-mqtt-component) is a combination of the following flags:

|  |  |
| --- | --- |
| 0x80 | Digital Signature |
| 0x40 | Non-Repudiation |
| 0x20 | Key Encipherment |
| 0x10 | Data Encipherment |
| 0x08 | Key Agreement |
| 0x04 | Certificate Signing |
| 0x02 | CRL Signing |
| 0x01 | Encipher Only |

Please see the [SSLCertUsage](#sslcertusage-property-mqtt-component) property for a text representation of [SSLCertUsageFlags](#sslcertusageflags-property-mqtt-component).

This functionality currently is not available when the provider is OpenSSL.

This property is read-only.

## Data Type

Integer

# SSLCertVersion Property ([MQTT](#mqtt-component) Component)

The certificate's version number.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLCertVersion = { read=FSSLCertVersion };
```

## Default Value

""

## Remarks

The certificate's version number. The possible values are the strings "V1", "V2", and "V3".

This property is read-only.

## Data Type

String

# SSLCertSubject Property ([MQTT](#mqtt-component) Component)

The subject of the certificate used for client authentication.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLCertSubject = { read=FSSLCertSubject, write=FSetSSLCertSubject };
```

## Default Value

""

## Remarks

The subject of the certificate used for client authentication.

This property must be set after all other certificate properties are set. When this property is set, a search is performed in the current certificate store to locate a certificate with a matching subject.

If a matching certificate is found, the property is set to the full subject of the matching certificate.

If an exact match is not found, the store is searched for subjects containing the value of the property.

If a match is still not found, the property is set to an empty string, and no certificate is selected.

The special value "*" picks a random certificate in the certificate store.

The certificate subject is a comma-separated list of distinguished name fields and values. For instance, "CN=www.server.com, OU=test, C=US, E=example@email.com". Common fields and their meanings are as follows:

| Field | Meaning |
| --- | --- |
| CN | Common Name. This is commonly a hostname like www.server.com. |
| O | Organization |
| OU | Organizational Unit |
| L | Locality |
| S | State |
| C | Country |
| E | Email Address |

If a field value contains a comma, it must be quoted.

## Data Type

String

# SSLCertEncoded Property ([MQTT](#mqtt-component) Component)

The certificate (PEM/Base64 encoded).

## Syntax

*C++ Builder Syntax*

```text
__property String SSLCertEncoded = { read=FSSLCertEncoded, write=FSetSSLCertEncoded };
__property DynamicArray<Byte> SSLCertEncodedB = { read=FSSLCertEncodedB, write=FSetSSLCertEncodedB };
```

## Default Value

""

## Remarks

The certificate (PEM/Base64 encoded). This property is used to assign a specific certificate. The [SSLCertStore](#sslcertstore-property-mqtt-component) and [SSLCertSubject](#sslcertsubject-property-mqtt-component) properties also may be used to specify a certificate.

When [SSLCertEncoded](#sslcertencoded-property-mqtt-component) is set, a search is initiated in the current [SSLCertStore](#sslcertstore-property-mqtt-component) for the private key of the certificate. If the key is found, [SSLCertSubject](#sslcertsubject-property-mqtt-component) is updated to reflect the full subject of the selected certificate; otherwise, [SSLCertSubject](#sslcertsubject-property-mqtt-component) is set to an empty string.

This property is not available at design time.

## Data Type

Byte Array

# SSLEnabled Property ([MQTT](#mqtt-component) Component)

This property indicates whether Transport Layer Security/Secure Sockets Layer (TLS/SSL) is enabled.

## Syntax

*C++ Builder Syntax*

```text
__property bool SSLEnabled = { read=FSSLEnabled, write=FSetSSLEnabled };
```

## Default Value

False

## Remarks

This property specifies whether TLS/SSL is enabled in the component. When False (default), the component operates in plaintext mode. When True, TLS/SSL is enabled.

TLS/SSL may also be enabled by setting SSLStartMode. Setting SSLStartMode will automatically update this property value.

This property is not available at design time.

## Data Type

Boolean

# SSLProvider Property ([MQTT](#mqtt-component) Component)

The Secure Sockets Layer/Transport Layer Security (SSL/TLS) implementation to use.

## Syntax

*C++ Builder Syntax*

```text
__property TiotMQTTSSLProviders SSLProvider = { read=FSSLProvider, write=FSetSSLProvider };
enum TiotMQTTSSLProviders {
  sslpAutomatic=0,
  sslpPlatform=1,
  sslpInternal=2
};
```

## Default Value

sslpAutomatic

## Remarks

This property specifies the SSL/TLS implementation to use. In most cases the default value of *0* (Automatic) is recommended and should not be changed. When set to *0* (Automatic), the component will select whether to use the platform implementation or the internal implementation depending on the operating system as well as the TLS version being used.

Possible values are as follows:

|  |  |
| --- | --- |
| 0 (sslpAutomatic - default) | Automatically selects the appropriate implementation. |
| 1 (sslpPlatform) | Uses the platform/system implementation. |
| 2 (sslpInternal) | Uses the internal implementation. |

 **Additional Notes**

In most cases using the default value (Automatic) is recommended. The component will select a provider depending on the current platform.

When Automatic is selected, the platform implementation is used by default. When TLS 1.3 is enabled via [SSLEnabledProtocols](#SSLEnabledProtocols), the component will always try and use the platform implementation. If the platform TLS 1.3 implementation is not available, the internal implementation will be used.

## Data Type

Integer

# SSLServerCertEffectiveDate Property ([MQTT](#mqtt-component) Component)

The date on which this certificate becomes valid.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLServerCertEffectiveDate = { read=FSSLServerCertEffectiveDate };
```

## Default Value

""

## Remarks

The date on which this certificate becomes valid. Before this date, it is not valid. The date is localized to the system's time zone. The following example illustrates the format of an encoded date:

23-Jan-2000 15:00:00.

This property is read-only.

## Data Type

String

# SSLServerCertExpirationDate Property ([MQTT](#mqtt-component) Component)

The date on which the certificate expires.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLServerCertExpirationDate = { read=FSSLServerCertExpirationDate };
```

## Default Value

""

## Remarks

The date on which the certificate expires. After this date, the certificate will no longer be valid. The date is localized to the system's time zone. The following example illustrates the format of an encoded date:

23-Jan-2001 15:00:00.

This property is read-only.

## Data Type

String

# SSLServerCertExtendedKeyUsage Property ([MQTT](#mqtt-component) Component)

A comma-delimited list of extended key usage identifiers.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLServerCertExtendedKeyUsage = { read=FSSLServerCertExtendedKeyUsage };
```

## Default Value

""

## Remarks

A comma-delimited list of extended key usage identifiers. These are the same as ASN.1 object identifiers (OIDs).

This property is read-only.

## Data Type

String

# SSLServerCertFingerprint Property ([MQTT](#mqtt-component) Component)

The hex-encoded, 16-byte MD5 fingerprint of the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLServerCertFingerprint = { read=FSSLServerCertFingerprint };
```

## Default Value

""

## Remarks

The hex-encoded, 16-byte MD5 fingerprint of the certificate. This property is primarily used for keys which do not have a corresponding X.509 public certificate, such as PEM keys that only contain a private key. It is commonly used for SSH keys.

The following example illustrates the format: *bc:2a:72:af:fe:58:17:43:7a:5f:ba:5a:7c:90:f7:02*

This property is read-only.

## Data Type

String

# SSLServerCertFingerprintSHA1 Property ([MQTT](#mqtt-component) Component)

The hex-encoded, 20-byte SHA-1 fingerprint of the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLServerCertFingerprintSHA1 = { read=FSSLServerCertFingerprintSHA1 };
```

## Default Value

""

## Remarks

The hex-encoded, 20-byte SHA-1 fingerprint of the certificate. This property is primarily used for keys which do not have a corresponding X.509 public certificate, such as PEM keys that only contain a private key. It is commonly used for SSH keys.

The following example illustrates the format: *30:7b:fa:38:65:83:ff:da:b4:4e:07:3f:17:b8:a4:ed:80:be:ff:84*

This property is read-only.

## Data Type

String

# SSLServerCertFingerprintSHA256 Property ([MQTT](#mqtt-component) Component)

The hex-encoded, 32-byte SHA-256 fingerprint of the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLServerCertFingerprintSHA256 = { read=FSSLServerCertFingerprintSHA256 };
```

## Default Value

""

## Remarks

The hex-encoded, 32-byte SHA-256 fingerprint of the certificate. This property is primarily used for keys which do not have a corresponding X.509 public certificate, such as PEM keys that only contain a private key. It is commonly used for SSH keys.

The following example illustrates the format: *6a:80:5c:33:a9:43:ea:b0:96:12:8a:64:96:30:ef:4a:8a:96:86:ce:f4:c7:be:10:24:8e:2b:60:9e:f3:59:53*

This property is read-only.

## Data Type

String

# SSLServerCertIssuer Property ([MQTT](#mqtt-component) Component)

The issuer of the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLServerCertIssuer = { read=FSSLServerCertIssuer };
```

## Default Value

""

## Remarks

The issuer of the certificate. This property contains a string representation of the name of the issuing authority for the certificate.

This property is read-only.

## Data Type

String

# SSLServerCertPrivateKey Property ([MQTT](#mqtt-component) Component)

The private key of the certificate (if available).

## Syntax

*C++ Builder Syntax*

```text
__property String SSLServerCertPrivateKey = { read=FSSLServerCertPrivateKey };
```

## Default Value

""

## Remarks

The private key of the certificate (if available). The key is provided as PEM/Base64-encoded data.

NOTE: The [SSLServerCertPrivateKey](#sslservercertprivatekey-property-mqtt-component) may be available but not exportable. In this case, [SSLServerCertPrivateKey](#sslservercertprivatekey-property-mqtt-component) returns an empty string.

This property is read-only.

## Data Type

String

# SSLServerCertPrivateKeyAvailable Property ([MQTT](#mqtt-component) Component)

Whether a PrivateKey is available for the selected certificate.

## Syntax

*C++ Builder Syntax*

```text
__property bool SSLServerCertPrivateKeyAvailable = { read=FSSLServerCertPrivateKeyAvailable };
```

## Default Value

false

## Remarks

Whether a [SSLServerCertPrivateKey](#sslservercertprivatekey-property-mqtt-component) is available for the selected certificate. If [SSLServerCertPrivateKeyAvailable](#sslservercertprivatekeyavailable-property-mqtt-component) is True, the certificate may be used for authentication purposes (e.g., server authentication).

This property is read-only.

## Data Type

Boolean

# SSLServerCertPrivateKeyContainer Property ([MQTT](#mqtt-component) Component)

The name of the PrivateKey container for the certificate (if available).

## Syntax

*C++ Builder Syntax*

```text
__property String SSLServerCertPrivateKeyContainer = { read=FSSLServerCertPrivateKeyContainer };
```

## Default Value

""

## Remarks

The name of the [SSLServerCertPrivateKey](#sslservercertprivatekey-property-mqtt-component) container for the certificate (if available). This functionality is available only on Windows platforms.

This property is read-only.

## Data Type

String

# SSLServerCertPublicKey Property ([MQTT](#mqtt-component) Component)

The public key of the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLServerCertPublicKey = { read=FSSLServerCertPublicKey };
```

## Default Value

""

## Remarks

The public key of the certificate. The key is provided as PEM/Base64-encoded data.

This property is read-only.

## Data Type

String

# SSLServerCertPublicKeyAlgorithm Property ([MQTT](#mqtt-component) Component)

The textual description of the certificate's public key algorithm.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLServerCertPublicKeyAlgorithm = { read=FSSLServerCertPublicKeyAlgorithm };
```

## Default Value

""

## Remarks

The textual description of the certificate's public key algorithm. The property contains either the name of the algorithm (e.g., "RSA" or "RSA_DH") or an object identifier (OID) string representing the algorithm.

This property is read-only.

## Data Type

String

# SSLServerCertPublicKeyLength Property ([MQTT](#mqtt-component) Component)

The length of the certificate's public key (in bits).

## Syntax

*C++ Builder Syntax*

```text
__property int SSLServerCertPublicKeyLength = { read=FSSLServerCertPublicKeyLength };
```

## Default Value

0

## Remarks

The length of the certificate's public key (in bits). Common values are 512, 1024, and 2048.

This property is read-only.

## Data Type

Integer

# SSLServerCertSerialNumber Property ([MQTT](#mqtt-component) Component)

The serial number of the certificate encoded as a string.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLServerCertSerialNumber = { read=FSSLServerCertSerialNumber };
```

## Default Value

""

## Remarks

The serial number of the certificate encoded as a string. The number is encoded as a series of hexadecimal digits, with each pair representing a byte of the serial number.

This property is read-only.

## Data Type

String

# SSLServerCertSignatureAlgorithm Property ([MQTT](#mqtt-component) Component)

The text description of the certificate's signature algorithm.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLServerCertSignatureAlgorithm = { read=FSSLServerCertSignatureAlgorithm };
```

## Default Value

""

## Remarks

The text description of the certificate's signature algorithm. The property contains either the name of the algorithm (e.g., "RSA" or "RSA_MD5RSA") or an object identifier (OID) string representing the algorithm.

This property is read-only.

## Data Type

String

# SSLServerCertStore Property ([MQTT](#mqtt-component) Component)

The name of the certificate store for the client certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLServerCertStore = { read=FSSLServerCertStore };
__property DynamicArray<Byte> SSLServerCertStoreB = { read=FSSLServerCertStoreB };
```

## Default Value

"MY"

## Remarks

The name of the certificate store for the client certificate.

The [SSLServerCertStoreType](#sslservercertstoretype-property-mqtt-component) property denotes the type of the certificate store specified by [SSLServerCertStore](#sslservercertstore-property-mqtt-component). If the store is password-protected, specify the password in [SSLServerCertStorePassword](#sslservercertstorepassword-property-mqtt-component).

[SSLServerCertStore](#sslservercertstore-property-mqtt-component) is used in conjunction with the [SSLServerCertSubject](#sslservercertsubject-property-mqtt-component) property to specify client certificates. If [SSLServerCertStore](#sslservercertstore-property-mqtt-component) has a value, and [SSLServerCertSubject](#sslservercertsubject-property-mqtt-component) or [SSLServerCertEncoded](#sslservercertencoded-property-mqtt-component) is set, a search for a certificate is initiated. Please see the [SSLServerCertSubject](#sslservercertsubject-property-mqtt-component) property for details.

 Designations of certificate stores are platform dependent.

The following designations are the most common User and Machine certificate stores in Windows:

|  |  |
| --- | --- |
| MY | A certificate store holding personal certificates with their associated private keys. |
| CA | Certifying authority certificates. |
| ROOT | Root certificates. |

When the certificate store type is *cstPFXFile*, this property must be set to the name of the file. When the type is *cstPFXBlob*, the property must be set to the binary contents of a PFX file (i.e., PKCS#12 certificate store).

This property is read-only.

## Data Type

Byte Array

# SSLServerCertStorePassword Property ([MQTT](#mqtt-component) Component)

If the type of certificate store requires a password, this property is used to specify the password needed to open the certificate store.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLServerCertStorePassword = { read=FSSLServerCertStorePassword };
```

## Default Value

""

## Remarks

If the type of certificate store requires a password, this property is used to specify the password needed to open the certificate store.

This property is read-only.

## Data Type

String

# SSLServerCertStoreType Property ([MQTT](#mqtt-component) Component)

The type of certificate store for this certificate.

## Syntax

*C++ Builder Syntax*

```text
__property TiotMQTTSSLServerCertStoreTypes SSLServerCertStoreType = { read=FSSLServerCertStoreType };
enum TiotMQTTSSLServerCertStoreTypes {
  cstUser=0,
  cstMachine=1,
  cstPFXFile=2,
  cstPFXBlob=3,
  cstJKSFile=4,
  cstJKSBlob=5,
  cstPEMKeyFile=6,
  cstPEMKeyBlob=7,
  cstPublicKeyFile=8,
  cstPublicKeyBlob=9,
  cstSSHPublicKeyBlob=10,
  cstP7BFile=11,
  cstP7BBlob=12,
  cstSSHPublicKeyFile=13,
  cstPPKFile=14,
  cstPPKBlob=15,
  cstXMLFile=16,
  cstXMLBlob=17,
  cstJWKFile=18,
  cstJWKBlob=19,
  cstSecurityKey=20,
  cstBCFKSFile=21,
  cstBCFKSBlob=22,
  cstPKCS11=23,
  cstAuto=99
};
```

## Default Value

cstUser

## Remarks

The type of certificate store for this certificate.

 The component supports both public and private keys in a variety of formats. When the *cstAuto* value is used, the component will automatically determine the type. This property can take one of the following values:

```csharp
sftp.SSHCert = new Certificate(CertStoreTypes.cstPKCS11,
                               @"C:\Program Files\OpenSC Project\OpenSC\pkcs11\opensc-pkcs11.dll",
                               "123456", // PIN
                               "CN=cert_subject");
sftp.SSHUser = "test";
sftp.SSHLogon("myhost", 22);
```

```csharp
certmgr.CertStoreType = CertStoreTypes.cstPKCS11;
certmgr.OnCertList += (s, e) => {
  secKeyBlob = e.CertEncoded;
};
certmgr.CertStore = @"C:\Program Files\OpenSC Project\OpenSC\pkcs11\opensc-pkcs11.dll";
certmgr.CertStorePassword = "123456"; // PIN
certmgr.ListStoreCertificates();

sftp.SSHCert = new Certificate(CertStoreTypes.cstPKCS11, secKeyBlob, "123456", "*");
sftp.SSHUser = "test";
sftp.SSHLogon("myhost", 22);
```

|  |  |
| --- | --- |
| 0 (cstUser - default) | For Windows, this specifies that the certificate store is a certificate store owned by the current user. NOTE: This store type is not available in Java. |
| 1 (cstMachine) | For Windows, this specifies that the certificate store is a machine store. NOTE: This store type is not available in Java. |
| 2 (cstPFXFile) | The certificate store is the name of a PFX (PKCS#12) file containing certificates. |
| 3 (cstPFXBlob) | The certificate store is a string (binary or Base64-encoded) representing a certificate store in PFX (PKCS#12) format. |
| 4 (cstJKSFile) | The certificate store is the name of a Java Key Store (JKS) file containing certificates. NOTE: This store type is only available in Java. |
| 5 (cstJKSBlob) | The certificate store is a string (binary or Base64-encoded) representing a certificate store in Java Key Store (JKS) format. NOTE: This store type is only available in Java. |
| 6 (cstPEMKeyFile) | The certificate store is the name of a PEM-encoded file that contains a private key and an optional certificate. |
| 7 (cstPEMKeyBlob) | The certificate store is a string (binary or Base64-encoded) that contains a private key and an optional certificate. |
| 8 (cstPublicKeyFile) | The certificate store is the name of a file that contains a PEM- or DER-encoded public key certificate. |
| 9 (cstPublicKeyBlob) | The certificate store is a string (binary or Base64-encoded) that contains a PEM- or DER-encoded public key certificate. |
| 10 (cstSSHPublicKeyBlob) | The certificate store is a string (binary or Base64-encoded) that contains an SSH-style public key. |
| 11 (cstP7BFile) | The certificate store is the name of a PKCS#7 file containing certificates. |
| 12 (cstP7BBlob) | The certificate store is a string (binary) representing a certificate store in PKCS#7 format. |
| 13 (cstSSHPublicKeyFile) | The certificate store is the name of a file that contains an SSH-style public key. |
| 14 (cstPPKFile) | The certificate store is the name of a file that contains a PPK (PuTTY Private Key). |
| 15 (cstPPKBlob) | The certificate store is a string (binary) that contains a PPK (PuTTY Private Key). |
| 16 (cstXMLFile) | The certificate store is the name of a file that contains a certificate in XML format. |
| 17 (cstXMLBlob) | The certificate store is a string that contains a certificate in XML format. |
| 18 (cstJWKFile) | The certificate store is the name of a file that contains a JWK (JSON Web Key). |
| 19 (cstJWKBlob) | The certificate store is a string that contains a JWK (JSON Web Key). |
| 21 (cstBCFKSFile) | The certificate store is the name of a file that contains a BCFKS (Bouncy Castle FIPS Key Store). NOTE: This store type is only available in Java and .NET. |
| 22 (cstBCFKSBlob) | The certificate store is a string (binary or Base64-encoded) representing a certificate store in BCFKS (Bouncy Castle FIPS Key Store) format. NOTE: This store type is only available in Java and .NET. |
| 23 (cstPKCS11) | The certificate is present on a physical security key accessible via a PKCS#11 interface. To use a security key, create a new [Certificate](#Type_Certificate) object and pass cstPKCS11 as the [SSLServerCertStoreType](#sslservercertstoretype-property-mqtt-component), the full path of the PKCS#11 DLL as the [SSLServerCertStore](#sslservercertstore-property-mqtt-component), and the PIN as the [SSLServerCertStorePassword](#sslservercertstorepassword-property-mqtt-component). Code Example. SSH Authentication with Security Key (without CertMgr): Alternatively, collect the necessary data using the [CertMgr](#CertMgr) component by calling the [ListStoreCertificates](#CertMgr_m_ListStoreCertificates) method after setting the corresponding properties accordingly. The certificate information returned in the [CertList](#CertMgr_e_CertList) event's CertEncoded parameter may be saved for later use. When using a certificate obtained with this approach, pass the previously saved security key information as the [SSLServerCertStore](#sslservercertstore-property-mqtt-component) and set [SSLServerCertStorePassword](#sslservercertstorepassword-property-mqtt-component) to the PIN. Code Example. SSH Authentication with Security Key (with CertMgr): |
| 99 (cstAuto) | The store type is automatically detected from the input data. This setting may be used with both public and private keys and can detect any of the supported formats automatically. |

This property is read-only.

## Data Type

Integer

# SSLServerCertSubjectAltNames Property ([MQTT](#mqtt-component) Component)

Comma-separated lists of alternative subject names for the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLServerCertSubjectAltNames = { read=FSSLServerCertSubjectAltNames };
```

## Default Value

""

## Remarks

Comma-separated lists of alternative subject names for the certificate.

This property is read-only.

## Data Type

String

# SSLServerCertThumbprintMD5 Property ([MQTT](#mqtt-component) Component)

The MD5 hash of the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLServerCertThumbprintMD5 = { read=FSSLServerCertThumbprintMD5 };
```

## Default Value

""

## Remarks

The MD5 hash of the certificate. It is primarily used for X.509 certificates. If the hash does not already exist, it is automatically computed.

This property is read-only.

## Data Type

String

# SSLServerCertThumbprintSHA1 Property ([MQTT](#mqtt-component) Component)

The SHA-1 hash of the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLServerCertThumbprintSHA1 = { read=FSSLServerCertThumbprintSHA1 };
```

## Default Value

""

## Remarks

The SHA-1 hash of the certificate. It is primarily used for X.509 certificates. If the hash does not already exist, it is automatically computed.

This property is read-only.

## Data Type

String

# SSLServerCertThumbprintSHA256 Property ([MQTT](#mqtt-component) Component)

The SHA-256 hash of the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLServerCertThumbprintSHA256 = { read=FSSLServerCertThumbprintSHA256 };
```

## Default Value

""

## Remarks

The SHA-256 hash of the certificate. It is primarily used for X.509 certificates. If the hash does not already exist, it is automatically computed.

This property is read-only.

## Data Type

String

# SSLServerCertUsage Property ([MQTT](#mqtt-component) Component)

The text description of UsageFlags .

## Syntax

*C++ Builder Syntax*

```text
__property String SSLServerCertUsage = { read=FSSLServerCertUsage };
```

## Default Value

""

## Remarks

The text description of [SSLServerCertUsageFlags](#sslservercertusageflags-property-mqtt-component).

This value will be one or more of the following strings and will be separated by commas:

- Digital Signature
- Non-Repudiation
- Key Encipherment
- Data Encipherment
- Key Agreement
- Certificate Signing
- CRL Signing
- Encipher Only

If the provider is OpenSSL, the value is a comma-separated list of X.509 certificate extension names.

This property is read-only.

## Data Type

String

# SSLServerCertUsageFlags Property ([MQTT](#mqtt-component) Component)

The flags that show intended use for the certificate.

## Syntax

*C++ Builder Syntax*

```text
__property int SSLServerCertUsageFlags = { read=FSSLServerCertUsageFlags };
```

## Default Value

0

## Remarks

The flags that show intended use for the certificate. The value of [SSLServerCertUsageFlags](#sslservercertusageflags-property-mqtt-component) is a combination of the following flags:

|  |  |
| --- | --- |
| 0x80 | Digital Signature |
| 0x40 | Non-Repudiation |
| 0x20 | Key Encipherment |
| 0x10 | Data Encipherment |
| 0x08 | Key Agreement |
| 0x04 | Certificate Signing |
| 0x02 | CRL Signing |
| 0x01 | Encipher Only |

Please see the [SSLServerCertUsage](#sslservercertusage-property-mqtt-component) property for a text representation of [SSLServerCertUsageFlags](#sslservercertusageflags-property-mqtt-component).

This functionality currently is not available when the provider is OpenSSL.

This property is read-only.

## Data Type

Integer

# SSLServerCertVersion Property ([MQTT](#mqtt-component) Component)

The certificate's version number.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLServerCertVersion = { read=FSSLServerCertVersion };
```

## Default Value

""

## Remarks

The certificate's version number. The possible values are the strings "V1", "V2", and "V3".

This property is read-only.

## Data Type

String

# SSLServerCertSubject Property ([MQTT](#mqtt-component) Component)

The subject of the certificate used for client authentication.

## Syntax

*C++ Builder Syntax*

```text
__property String SSLServerCertSubject = { read=FSSLServerCertSubject };
```

## Default Value

""

## Remarks

The subject of the certificate used for client authentication.

This property must be set after all other certificate properties are set. When this property is set, a search is performed in the current certificate store to locate a certificate with a matching subject.

If a matching certificate is found, the property is set to the full subject of the matching certificate.

If an exact match is not found, the store is searched for subjects containing the value of the property.

If a match is still not found, the property is set to an empty string, and no certificate is selected.

The special value "*" picks a random certificate in the certificate store.

The certificate subject is a comma-separated list of distinguished name fields and values. For instance, "CN=www.server.com, OU=test, C=US, E=example@email.com". Common fields and their meanings are as follows:

| Field | Meaning |
| --- | --- |
| CN | Common Name. This is commonly a hostname like www.server.com. |
| O | Organization |
| OU | Organizational Unit |
| L | Locality |
| S | State |
| C | Country |
| E | Email Address |

If a field value contains a comma, it must be quoted.

This property is read-only.

## Data Type

String

# SSLServerCertEncoded Property ([MQTT](#mqtt-component) Component)

The certificate (PEM/Base64 encoded).

## Syntax

*C++ Builder Syntax*

```text
__property String SSLServerCertEncoded = { read=FSSLServerCertEncoded };
__property DynamicArray<Byte> SSLServerCertEncodedB = { read=FSSLServerCertEncodedB };
```

## Default Value

""

## Remarks

The certificate (PEM/Base64 encoded). This property is used to assign a specific certificate. The [SSLServerCertStore](#sslservercertstore-property-mqtt-component) and [SSLServerCertSubject](#sslservercertsubject-property-mqtt-component) properties also may be used to specify a certificate.

When [SSLServerCertEncoded](#sslservercertencoded-property-mqtt-component) is set, a search is initiated in the current [SSLServerCertStore](#sslservercertstore-property-mqtt-component) for the private key of the certificate. If the key is found, [SSLServerCertSubject](#sslservercertsubject-property-mqtt-component) is updated to reflect the full subject of the selected certificate; otherwise, [SSLServerCertSubject](#sslservercertsubject-property-mqtt-component) is set to an empty string.

This property is read-only and not available at design time.

## Data Type

Byte Array

# Timeout Property ([MQTT](#mqtt-component) Component)

This property includes the timeout for the component.

## Syntax

*C++ Builder Syntax*

```text
__property int Timeout = { read=FTimeout, write=FSetTimeout };
```

## Default Value

60

## Remarks

If the Timeout property is set to 0, all operations return immediately, potentially failing with a *WOULDBLOCK* error if data cannot be sent immediately.

If Timeout is set to a positive value, data is sent in a blocking manner and the component will wait for the operation to complete before returning control. The component will handle any potential *WOULDBLOCK* errors internally and automatically retry the operation for a maximum of Timeout seconds.

The component will use [DoEvents](#doevents-method-mqtt-component) to enter an efficient wait loop during any potential waiting period, making sure that all system events are processed immediately as they arrive. This ensures that the host application does not freeze and remains responsive.

If Timeout expires, and the operation is not yet complete, the component raises an exception.

NOTE: By default, all timeouts are *inactivity timeouts*, that is, the timeout period is extended by Timeout seconds when any amount of data is successfully sent or received.

The default value for the Timeout property is 60 seconds.

## Data Type

Integer

# User Property ([MQTT](#mqtt-component) Component)

A username if authentication is to be used.

## Syntax

*C++ Builder Syntax*

```text
__property String User = { read=FUser, write=FSetUser };
```

## Default Value

""

## Remarks

This property can be set to a username if authentication is to be used.

In MQTT 3.1.1, while a User may be specified without a [Password](#password-property-mqtt-component), setting a [Password](#password-property-mqtt-component) without a User is not supported; attempting to do so will cause the server to reject the connection attempt.

In MQTT 5, a [Password](#password-property-mqtt-component) may be set without a User, allowing the field to be used for credentials other than a password.

This property is not available at design time.

## Data Type

String

# Version Property ([MQTT](#mqtt-component) Component)

The MQTT protocol version that the component will conform to.

## Syntax

*C++ Builder Syntax*

```text
__property TiotMQTTVersions Version = { read=FVersion, write=FSetVersion };
enum TiotMQTTVersions {
  mvV3=0,
  mvV5=1
};
```

## Default Value

mvV3

## Remarks

This property specifies the version of the MQTT protocol to use. Possible values are:

|  |  |
| --- | --- |
| 0 (mvV3 - default) | MQTT 3.1.1 |
| 1 (mvV5) | MQTT 5 |

 This property must be set before connecting.

This property is not available at design time.

## Data Type

Integer

# WillMessage Property ([MQTT](#mqtt-component) Component)

The message that the server should publish in the event of an ungraceful disconnection.

## Syntax

*C++ Builder Syntax*

```text
__property String WillMessage = { read=FWillMessage, write=FSetWillMessage };
```

## Default Value

""

## Remarks

This property may be set before calling [Connect](#connect-method-mqtt-component) to specify to the server a message that should be published on [WillTopic](#willtopic-property-mqtt-component) if the connection is closed ungracefully. Since it is sent to the server when [Connect](#connect-method-mqtt-component) is called, this property's value cannot be changed when already connected.

Note that the WillMessage will only be sent to the server when [Connect](#connect-method-mqtt-component) is called if [WillTopic](#willtopic-property-mqtt-component) is set.

Refer to [WillTopic](#willtopic-property-mqtt-component) for more information about MQTT Will functionality.

This property is not available at design time.

## Data Type

String

# WillTopic Property ([MQTT](#mqtt-component) Component)

The topic that the server should publish the WillMessage to in the event of an ungraceful disconnection.

## Syntax

*C++ Builder Syntax*

```text
__property String WillTopic = { read=FWillTopic, write=FSetWillTopic };
```

## Default Value

""

## Remarks

This property may be set before calling [Connect](#connect-method-mqtt-component) to specify the topic name that the server should publish the [WillMessage](#willmessage-property-mqtt-component) on if the connection is closed ungracefully. Since it is sent to the server when [Connect](#connect-method-mqtt-component) is called, this property's value cannot be changed when already connected.

### MQTT Wills

The Will feature of MQTT allows a client to specify to the server a [WillMessage](#willmessage-property-mqtt-component) to publish (as well as a WillTopic to publish it on) in the event of an ungraceful disconnection.

An "ungraceful disconnection" is any disconnection *other than* one triggered by calling [Disconnect](#disconnect-method-mqtt-component) (in which case the server discards the Will message without publishing it). Note that in MQTT 5, the client can set a [DisconnectReasonCode](#DisconnectReasonCode) of *0x04* before calling [Disconnect](#disconnect-method-mqtt-component) to instruct the server to publish the Will message anyway.

In addition to the WillTopic and [WillMessage](#willmessage-property-mqtt-component) properties, the [WillQOS](#WillQOS) setting may be used to specify the Will message's QoS level, and the [WillRetain](#WillRetain) setting to set the Will message's Retain flag. Refer to those settings for more information.

If WillTopic is set to empty string (default) when [Connect](#connect-method-mqtt-component) is called, the component *will not* send a Will to the server.

In MQTT 5, the "WillDelayInterval" value in the [WillProperties](#WillProperties) config can specify a delay between the ending of the connection and sending the will message, so that the [WillMessage](#willmessage-property-mqtt-component) will not be sent if a connection is re-established within a certain period of time.

This property is not available at design time.

## Data Type

String

# Config Method ([MQTT](#mqtt-component) Component)

Sets or retrieves a configuration setting.

## Syntax

*C++ Builder Syntax*

```text
String __fastcall Config(String ConfigurationString);
```

## Remarks

Config is a generic method available in every component. It is used to set and retrieve [configuration settings](#config-settings-mqtt-component) for the component.

These settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the component, access to these *internal properties* is provided through the Config method.

To set a configuration setting named *PROPERTY*, you must call *Config("PROPERTY=VALUE")*, where *VALUE* is the value of the setting expressed as a string. For boolean values, use the strings "True", "False", "0", "1", "Yes", or "No" (case does not matter).

To read (query) the value of a [configuration setting](#config-settings-mqtt-component), you must call *Config("PROPERTY")*. The value will be returned as a string.

# Connect Method ([MQTT](#mqtt-component) Component)

Connects to the remote host.

## Syntax

*C++ Builder Syntax*

```text
void __fastcall Connect();
```

## Remarks

This method connects to the remote host specified by [RemoteHost](#remotehost-property-mqtt-component) and [RemotePort](#remoteport-property-mqtt-component).

By default the component will connect in plaintext. To enable SSL set [SSLEnabled](#sslenabled-property-mqtt-component) to True.

In addition, WebSocket connections are supported. To connect using WebSockets specify a hostname beginning with *ws://* (plaintext) or *wss://* (SSL). For instance, *ws://test.mosquitto.org*.

When connecting to an MQTT server, the component sends the following information:

- The values of the [ClientId](#clientid-property-mqtt-component), [CleanSession](#cleansession-property-mqtt-component), and [KeepAliveInterval](#keepaliveinterval-property-mqtt-component) properties.
- The value of the [User](#user-property-mqtt-component) property (if non-empty).
- The value of the [Password](#password-property-mqtt-component) property (if non-empty).
- The values of the [WillTopic](#willtopic-property-mqtt-component) and [WillMessage](#willmessage-property-mqtt-component) properties and the [WillQOS](#WillQOS) and [WillRetain](#WillRetain) configuration settings.
- MQTT 5 specific values from [ClientTopicAliasMax](#ClientTopicAliasMax), [SessionExpInterval](#SessionExpInterval), [ConnectProperties](#ConnectProperties) and [WillProperties](#WillProperties).

If [CleanSession](#cleansession-property-mqtt-component) is *True*, check the [SessionPresent](#SessionPresent) configuration setting once connected to determine whether the server actually had any session state saved.

Refer to [CleanSession](#cleansession-property-mqtt-component), [SaveSession](#savesession-method-mqtt-component), and [RestoreSession](#restoresession-method-mqtt-component) for more information about MQTT sessions and session state persistence; refer to [WillTopic](#willtopic-property-mqtt-component), [WillMessage](#willmessage-property-mqtt-component), [WillQOS](#WillQOS), and [WillRetain](#WillRetain) for more information about MQTT Wills.

**Basic Connection Example**

```csharp
mqtt1.ClientId = "testClient";
mqtt1.CleanSession = true;
mqtt1.KeepAliveInterval = 30;
mqtt1.WillTopic = "wills/" + mqtt1.ClientId;
mqtt1.WillMessage = mqtt1.ClientId + " was disconnected ungracefully!";
mqtt1.RemoteHost = "mqtt.test-server.com";
mqtt1.RemotePort = 1883;
mqtt1.Connect();
```

# ConnectTo Method ([MQTT](#mqtt-component) Component)

Connects to the remote host.

## Syntax

*C++ Builder Syntax*

```text
void __fastcall ConnectTo(String Host, int Port);
```

## Remarks

This method connects to the remote host specified by the *Host* and *Port* parameters. Calling this method is equivalent to setting the [RemoteHost](#remotehost-property-mqtt-component) property to *Host* and setting [RemotePort](#remoteport-property-mqtt-component) to *Port*.

By default the component will connect in plaintext. To enable SSL set [SSLEnabled](#sslenabled-property-mqtt-component) to True.

In addition, WebSocket connections are supported. To connect using WebSockets specify a hostname beginning with *ws://* (plaintext) or *wss://* (SSL). For instance, *ws://test.mosquitto.org*.

When connecting to an MQTT server, the component sends the following information:

- The values of the [ClientId](#clientid-property-mqtt-component), [CleanSession](#cleansession-property-mqtt-component), and [KeepAliveInterval](#keepaliveinterval-property-mqtt-component) properties.
- The value of the [User](#user-property-mqtt-component) property (if non-empty).
- The value of the [Password](#password-property-mqtt-component) property (if non-empty).
- The values of the [WillTopic](#willtopic-property-mqtt-component) and [WillMessage](#willmessage-property-mqtt-component) properties and the [WillQOS](#WillQOS) and [WillRetain](#WillRetain) configuration settings.
- MQTT 5 specific values from [ClientTopicAliasMax](#ClientTopicAliasMax), [SessionExpInterval](#SessionExpInterval), [ConnectProperties](#ConnectProperties) and [WillProperties](#WillProperties).

If [CleanSession](#cleansession-property-mqtt-component) is *True*, check the [SessionPresent](#SessionPresent) configuration setting once connected to determine whether the server actually had any session state saved.

Refer to [CleanSession](#cleansession-property-mqtt-component), [SaveSession](#savesession-method-mqtt-component), and [RestoreSession](#restoresession-method-mqtt-component) for more information about MQTT sessions and session state persistence; refer to [WillTopic](#willtopic-property-mqtt-component), [WillMessage](#willmessage-property-mqtt-component), [WillQOS](#WillQOS), and [WillRetain](#WillRetain) for more information about MQTT Wills.

**Basic Connection Example**

```csharp
mqtt1.ClientId = "testClient";
mqtt1.CleanSession = true;
mqtt1.KeepAliveInterval = 30;
mqtt1.WillTopic = "wills/" + mqtt1.ClientId;
mqtt1.WillMessage = mqtt1.ClientId + " was disconnected ungracefully!";
mqtt1.ConnectTo("mqtt.test-server.com", 1883);
```

# Disconnect Method ([MQTT](#mqtt-component) Component)

This method disconnects from the remote host.

## Syntax

*C++ Builder Syntax*

```text
void __fastcall Disconnect();
```

## Remarks

This method disconnects from the remote host.

Refer to the [Connected](#connected-property-mqtt-component) property for more information about MQTT-specific behavior.

# DoEvents Method ([MQTT](#mqtt-component) Component)

This method processes events from the internal message queue.

## Syntax

*C++ Builder Syntax*

```text
void __fastcall DoEvents();
```

## Remarks

When DoEvents is called, the component processes any available events. If no events are available, it waits for a preset period of time, and then returns.

# Interrupt Method ([MQTT](#mqtt-component) Component)

Interrupt the current action and disconnects from the remote host.

## Syntax

*C++ Builder Syntax*

```text
void __fastcall Interrupt();
```

## Remarks

This method will interrupt the current method (if applicable) and cause the component to disconnect from the remote host.

# PublishData Method ([MQTT](#mqtt-component) Component)

Publishes a message with a raw data payload.

## Syntax

*C++ Builder Syntax*

```text
void __fastcall PublishData(String Topic, int QOS, DynamicArray<Byte> Data);
```

## Remarks

This method publishes an MQTT message with a raw data payload to the specified *Topic* at a given *QOS* level.

**Publish Examples**

```csharp
// Publish a simple string-based message.
mqtt1.PublishMessage("/home/floor1/security/camera2", 1, "Cat detected!");

// Publish a raw data message.
byte[] catPicture = ...;
mqtt1.PublishData("/home/floor1/security/camera2", 1, catPicture);
```

The [Retain](#Retain) configuration setting may be set before calling this method in order to publish a retained message (see [Retain](#Retain) for more information).

### Topic Names

Topic names are case-sensitive, must be 1-65535 characters long, and may include any characters *except* wildcard characters (*#* and *+*) and the null character. The */* character separates levels within a topic name, which is important in the context of subscribing (see [Subscribe](#subscribe-method-mqtt-component) for more information).

Keep in mind that using topic names with leading or trailing */* characters will cause topic levels with zero-length names to be created. That is, a topic name like */a/b/* consists of the levels *''*, *'a'*, *'b'*, and *''*. Depending on the server, multiple successive */*s may also cause zero-length levels to be created, or may be treated as a single */*.

Topic names that begin with a *$* are "system topics", and servers will typically prevent clients from publishing to them.

For example, topic names that begin with *$share* are reserved for Shared Subscriptions (see [Subscribe](#subscribe-method-mqtt-component)).

### QoS Values

QoS values set the service level for delivery of a message. Values range from 0 to 2 and have the following meanings:

| QoS Level | Description |
| --- | --- |
| 0 | At most once - The published message is sent once, and if it does not arrive it is lost. |
| 1 | At least once - Guarantees that the published message arrives, but there may be duplicates. |
| 2 | Exactly once - Guarantees that the publish message arrives and that there are no duplicates. |

 For outgoing messages with a QoS of 0, the component sends a PUBLISH packet, but does *not* add the message to OutgoingMessages (since QoS 0 messages do not get acknowledged).

QoS is not guaranteed to be end-to-end in MQTT. The server must downgrade a message's QoS level when delivering it to clients who specified a lower "maximum acceptable" QoS when they subscribed. For example, if Client X subscribes to a topic at QoS 1, and Client Y publishes a message to that topic at QoS 2, the server will downgrade the message to QoS 1 when attempting to deliver it to Client X.

### Outbound Message Processing

Outgoing messages with a QoS of 1 follow these steps:

1. The component sends the PUBLISH packet, then adds the message to OutgoingMessages.
2. The component waits to receive a PUBACK (publish acknowledgment) packet.
3. The [MessageAck](#messageack-event-mqtt-component) event is fired.
4. The message is removed from OutgoingMessages.
5. The [MessageOut](#messageout-event-mqtt-component) event is fired.

Outgoing messages with a QoS of 2 follow these steps:

1. The component sends the PUBLISH packet, then adds the message to OutgoingMessages.
2. The component waits to receive a PUBREC (publish received) packet.
3. The component sends a PUBREL (publish release) packet in response.
4. The component waits to receive a PUBCOMP (publish complete) packet.
5. The [MessageAck](#messageack-event-mqtt-component) event is fired.
6. The message is removed from OutgoingMessages.
7. The [MessageOut](#messageout-event-mqtt-component) event is fired.

In MQTT 3.1.1, the [RepublishInterval](#RepublishInterval) configuration setting, if set to a non-zero value (default), controls how long the component will wait to receive a PUBACK (for QoS 1) or PUBREC (for QoS 2) before automatically republishing an outgoing message. In MQTT 5, messages are only republished if the client is disconnected before receiving a PUBACK or PUBREC.

**MQTT 5 Notes**

MQTT 5 makes a number of new features available when publishing messages, including:

- [TopicAlias](#TopicAlias) - Set an integer alias along with the topic name when first publishing a message. When publishing additional messages to the same topic if [TopicAlias](#TopicAlias) is set the *Topic* parameter does not need to be set. This reduces the size of the message sent to the server.
- Request / Response - Set a [ResponseTopic](#ResponseTopic) which identifies the topic to which a receiver should respond.

Some of these features require configuration settings to be set prior to publishing. In these cases, note that these configuration settings will continue to be applicable to any future PUBLISH packets sent with the method unless they are updated or reset. To prevent clear a previously set configuration setting, set it to *""*, or *-1* (for integers).

See the [OutgoingMessageProperties](#OutgoingMessageProperties) configuration setting for additional details.

# PublishMessage Method ([MQTT](#mqtt-component) Component)

Publishes a message with a string payload.

## Syntax

*C++ Builder Syntax*

```text
void __fastcall PublishMessage(String Topic, int QOS, String Message);
```

## Remarks

This method publishes an MQTT message with a string payload to the specified *Topic* at a given *QOS* level.

**Publish Examples**

```csharp
// Publish a simple string-based message.
mqtt1.PublishMessage("/home/floor1/security/camera2", 1, "Cat detected!");

// Publish a raw data message.
byte[] catPicture = ...;
mqtt1.PublishData("/home/floor1/security/camera2", 1, catPicture);
```

The [Retain](#Retain) configuration setting may be set before calling this method in order to publish a retained message (see [Retain](#Retain) for more information).

### Topic Names

Topic names are case-sensitive, must be 1-65535 characters long, and may include any characters *except* wildcard characters (*#* and *+*) and the null character. The */* character separates levels within a topic name, which is important in the context of subscribing (see [Subscribe](#subscribe-method-mqtt-component) for more information).

Keep in mind that using topic names with leading or trailing */* characters will cause topic levels with zero-length names to be created. That is, a topic name like */a/b/* consists of the levels *''*, *'a'*, *'b'*, and *''*. Depending on the server, multiple successive */*s may also cause zero-length levels to be created, or may be treated as a single */*.

Topic names that begin with a *$* are "system topics", and servers will typically prevent clients from publishing to them.

For example, topic names that begin with *$share* are reserved for Shared Subscriptions (see [Subscribe](#subscribe-method-mqtt-component)).

### QoS Values

QoS values set the service level for delivery of a message. Values range from 0 to 2 and have the following meanings:

| QoS Level | Description |
| --- | --- |
| 0 | At most once - The published message is sent once, and if it does not arrive it is lost. |
| 1 | At least once - Guarantees that the published message arrives, but there may be duplicates. |
| 2 | Exactly once - Guarantees that the publish message arrives and that there are no duplicates. |

 For outgoing messages with a QoS of 0, the component sends a PUBLISH packet, but does *not* add the message to OutgoingMessages (since QoS 0 messages do not get acknowledged).

QoS is not guaranteed to be end-to-end in MQTT. The server must downgrade a message's QoS level when delivering it to clients who specified a lower "maximum acceptable" QoS when they subscribed. For example, if Client X subscribes to a topic at QoS 1, and Client Y publishes a message to that topic at QoS 2, the server will downgrade the message to QoS 1 when attempting to deliver it to Client X.

### Outbound Message Processing

Outgoing messages with a QoS of 1 follow these steps:

1. The component sends the PUBLISH packet, then adds the message to OutgoingMessages.
2. The component waits to receive a PUBACK (publish acknowledgment) packet.
3. The [MessageAck](#messageack-event-mqtt-component) event is fired.
4. The message is removed from OutgoingMessages.
5. The [MessageOut](#messageout-event-mqtt-component) event is fired.

Outgoing messages with a QoS of 2 follow these steps:

1. The component sends the PUBLISH packet, then adds the message to OutgoingMessages.
2. The component waits to receive a PUBREC (publish received) packet.
3. The component sends a PUBREL (publish release) packet in response.
4. The component waits to receive a PUBCOMP (publish complete) packet.
5. The [MessageAck](#messageack-event-mqtt-component) event is fired.
6. The message is removed from OutgoingMessages.
7. The [MessageOut](#messageout-event-mqtt-component) event is fired.

In MQTT 3.1.1, the [RepublishInterval](#RepublishInterval) configuration setting, if set to a non-zero value (default), controls how long the component will wait to receive a PUBACK (for QoS 1) or PUBREC (for QoS 2) before automatically republishing an outgoing message. In MQTT 5, messages are only republished if the client is disconnected before receiving a PUBACK or PUBREC.

**MQTT 5 Notes**

MQTT 5 makes a number of new features available when publishing messages, including:

- [TopicAlias](#TopicAlias) - Set an integer alias along with the topic name when first publishing a message. When publishing additional messages to the same topic if [TopicAlias](#TopicAlias) is set the *Topic* parameter does not need to be set. This reduces the size of the message sent to the server.
- Request / Response - Set a [ResponseTopic](#ResponseTopic) which identifies the topic to which a receiver should respond.

Some of these features require configuration settings to be set prior to publishing. In these cases, note that these configuration settings will continue to be applicable to any future PUBLISH packets sent with the method unless they are updated or reset. To prevent clear a previously set configuration setting, set it to *""*, or *-1* (for integers).

See the [OutgoingMessageProperties](#OutgoingMessageProperties) configuration setting for additional details.

# Reset Method ([MQTT](#mqtt-component) Component)

This method will reset the component.

## Syntax

*C++ Builder Syntax*

```text
void __fastcall Reset();
```

## Remarks

This method will reset the component's properties to their default values.

# RestoreSession Method ([MQTT](#mqtt-component) Component)

Restores session state data.

## Syntax

*C++ Builder Syntax*

```text
void __fastcall RestoreSession(String StateData);
```

## Remarks

This method restores previously-saved session state data and sets [CleanSession](#cleansession-property-mqtt-component) to *False*. If the [SessionStateFile](#SessionStateFile) configuration setting is set, the component will use the contents of that file to restore the session state data, ignoring the string passed to this method.

Depending on the elapsed time between connections the server may discard any previously saved session data on its side.

In MQTT 3.1.1, the time after which the server discards saved session data is not defined in the protocol specification and may vary between implementations. As a result, when re-connecting it may not be known if the server is capable of restoring a previous session.

To determine if a session can be restored on connection, set [CleanSession](#cleansession-property-mqtt-component) to *False*, [ClientId](#clientid-property-mqtt-component) to the same value used in the initial connection, and call [ConnectTo](#connectto-method-mqtt-component).

When the [Connected](#connected-event-mqtt-component) event fires, query the [SessionPresent](#SessionPresent) configuration setting. If [SessionPresent](#SessionPresent) is *True* the session should be restored by calling RestoreSession. If [SessionPresent](#SessionPresent) is *False* the session should not be restored so that the connection proceeds as a clean session.

NOTE: Not all servers support the use of [SessionPresent](#SessionPresent).

**Restore Session Example (Query SessionPresent)**

```csharp
mqtt1.CleanSession = false;
mqtt1.ClientId = clientId;
mqtt1.OnConnected += (s, e) => {
  if (mqtt1.Config("SessionPresent").ToLower() == "true")
    mqtt1.RestoreSession(sessionStr);
};
mqtt1.ConnectTo(host,port);
```

If it is known that the server has not discarded the session state, for instance from familiarity with the server implementation and its behavior, then a simplified procedure can be performed. Simply set [ClientId](#clientid-property-mqtt-component) to the value used in the initial connection, call RestoreSession, and then call [ConnectTo](#connectto-method-mqtt-component).

**Restore Session Example (Server Status Known)**

```csharp
mqtt1.ClientId = clientId;
mqtt1.RestoreSession(sessionStr);
mqtt1.ConnectTo(host,port);
```

Refer to [CleanSession](#cleansession-property-mqtt-component) and [SaveSession](#savesession-method-mqtt-component) for more information.

**MQTT 5 Notes**

In MQTT 5, the time after which the server discards saved session data is controlled by the [SessionExpInterval](#SessionExpInterval). The server is required to store state data for the amount of time specified by this value, at which point it is required to delete it.

This feature allows the client to use its own time-based logic to determine whether it is necessary to call RestoreSession.

# SaveSession Method ([MQTT](#mqtt-component) Component)

Saves session state data.

## Syntax

*C++ Builder Syntax*

```text
String __fastcall SaveSession();
```

## Remarks

This method saves session state data currently held by the component, returning it as a string that can later be used to restore it. If the [SessionStateFile](#SessionStateFile) configuration setting is set, the component will also write the session state data to that file (creating and/or overwriting it, as necessary).

Refer to [CleanSession](#cleansession-property-mqtt-component) and [RestoreSession](#restoresession-method-mqtt-component) for more information.

# Subscribe Method ([MQTT](#mqtt-component) Component)

Subscribes the component to one or more topic filters.

## Syntax

*C++ Builder Syntax*

```text
void __fastcall Subscribe(String TopicFilter, int QOS);
```

## Remarks

This method subscribes the component to one or more topic filters using one or more QoS levels.

The [Subscribed](#subscribed-event-mqtt-component) event will fire once for each topic filter given once the server acknowledges the subscription request(s). Keep in mind that the server is allowed to start publishing messages *before it sends the acknowledgment*.

It is legal to call Subscribe again for the same topic filter at any time, and pass a different QoS value at that time if desired. The [Subscribed](#subscribed-event-mqtt-component) event will fire as normal when doing this.

**Subscribe Examples**

```csharp
// Subscribed event handler.
mqtt1.OnSubscribed += (s, e) => {
  if (e.ResponseCode <= 2)
    Console.WriteLine("Subscribed to " + e.TopicFilter + " at QoS " + e.QOS + ".");
  else
    Console.WriteLine("Failed to subscribe to " + e.TopicFilter + ".");
};

// Basic, subscribe to some topic filters, all at the same QoS level.
mqtt1.Subscribe("home,home/floor1/+/temperature,home/floor2/#", 2);

// A bit more advanced, subscribe to the same topic filters, but at different QoS levels.
mqtt1.Config("TopicQOSArray=1,2,2");
// The 0 is ignored here since we've specified individual QoS values explicitly.
mqtt1.Subscribe("home,home/floor1/+/temperature,home/floor2/#", 0);
```

### Topic Filters

The string passed for *TopicFilter* must contain one or more valid topic filter strings, separated by the delimiter string specified by the [TopicDelimiter](#TopicDelimiter) configuration setting (*,* by default).

A topic filter is a case-sensitive string between 1 and 65535 characters long (per topic filter), and can include any character other than the null character. Certain characters have special meanings:

- */* - The topic level separator
- *#* - The multi-level wildcard (zero or more levels)
- *+* - The single-level wildcard (exactly one level)
- Leading *$* - Denotes a "system topic"

Note that both types of wildcards may be used in the same topic filter.

**Topic Level Separators**

The topic level separator, as its name implies, is used to separate a topic name (or in this case, filter) into "levels". This concept of topic names having levels is what allows topic filters to match multiple topics through the use of wildcards. For the examples in the next sections, assume the following topics exist:

- *home/floor1*
- *home/floor1/livingRoom*
- *home/floor1/livingRoom/temperature*
- *home/floor1/kitchen/temperature*
- *home/floor1/kitchen/fridge/temperature*
- *home/floor2/bedroom1*
- *home/floor2/bedroom1/temperature*

**Multi-level Wildcards**

The multi-level wildcard character is used at the end of a topic filter to make it match an arbitrary number of successive levels. For example, the topic filter *home/floor1/#* would match the following topics:

- *home/floor1 (because it can match zero levels)*
- *home/floor1/livingRoom*
- *home/floor1/livingRoom/temperature*
- *home/floor1/kitchen/temperature*
- *home/floor1/kitchen/fridge/temperature*

Here are some things to keep in mind when using a multi-level wildcard:

- *#* must always be the last character in the topic filter (e.g., *home/floor1/#/livingRoom* is not valid)
- *#* must always be preceded by a */* (e.g., *home/floor1#* is not valid)
- *#* by itself is a valid topic filter, and will match all topics except system topics

**Single-level Wildcards**

The single-level wildcard character is used between two */*s in a topic filter to make it any single level. For example, the topic filter *home/floor1/+/temperature* would match the following topics:

- *home/floor1/livingRoom/temperature*
- *home/floor1/kitchen/temperature*

Any number of single-level wildcards are supported in a topic filter. For example, the topic filter *home/+/+/temperature* would match the following topics:

- *home/floor1/livingRoom/temperature*
- *home/floor1/kitchen/temperature*
- *home/floor2/bedroom1/temperature*

Here are some things to keep in mind when using single-level wildcards:

- *+* must always be separated from other levels using */*s (e.g., *home/floor1+* is invalid, but *+/floor1/+* is valid)
- *+* by itself is a valid topic filter, and will match all topics with exactly one level in their name except system topics
- Remember, topic names with a leading */* have a zero-length string as their first level. So a topic named */people* would be matched by the topic filter *+/+*, but *not* by *+*
- *+* *must* match *exactly* one level. So for example, the topic filter *home/floor1/kitchen/+/temperature* would match */home/floor1/kitchen/fridge/temperature*, but *not* *home/floor1/kitchen/temperature*

**System Topics**

Topic names which begin with a *$* are "system topics". Typically, the server prohibits clients from publishing to such topics, but permits subscribing to them. As described above, wildcards will *never* match the first level of a topic if it begins with a *$*.

Note that MQTT 5 defines shared subscriptions, a special type of system topic. See the MQTT 5 notes below for more.

### Requested QoS Values

The QoS value passed for *QOS* will be used to subscribe to all given topic filters, unless the [TopicQOSArray](#TopicQOSArray) configuration setting is used to specify explicit QoS values for each individual topic filter.

QoS values range from 0 to 2 and have the following meanings:

| QoS Level | Description |
| --- | --- |
| 0 | At most once - The published message is sent once, and if it does not arrive it is lost. |
| 1 | At least once - Guarantees that the published message arrives, but there may be duplicates. |
| 2 | Exactly once - Guarantees that the publish message arrives and that there are no duplicates. |

QoS is not guaranteed to be end-to-end in MQTT. The server must downgrade a message's QoS level when delivering it to clients who specified a lower "maximum acceptable" QoS when they subscribed. For example, if Client X subscribes to a topic at QoS 1, and Client Y publishes a message to that topic at QoS 2, the server will downgrade the message to QoS 1 when attempting to deliver it to Client X.

**MQTT 5 Notes**

MQTT 5 defines several new features that apply to subscriptions, including Shared Subscriptions, Subscription Options and Subscription Identifiers. Some of these features require configuration settings to be set prior to calling Subscribe. In these cases, note that thee configuration settings will continue to be applied to any future SUBSCRIBE packets sent with the method unless they are updated or reset. To prevent a value from being included in packets after it has been set previously, set it to *""*, or *-1* (for integers).

### Shared Subscriptions

Shared subscriptions allow a client to subscribe to a topic as a part of a group of clients, where each client in the group is subscribing to the same topic. Each message published to such a group will be delivered to only one client in the group, making shared subscriptions useful when several clients share the processing of the publications in parallel.

Subscribing to a topic as part of a shared subscription is similar to a normal subscription, the only difference being the syntax of the topic filter passed to the Subscribe method.

The format of this filter is *$share/{ShareName}/{filter}*, where

- *$share* is a string literal identifying the subscription as a shared subscriptions.
- *{ShareName}* is a string at least one character long that must not include */*, *+* or *#*.
- *{filter}* is a full topic filter formatted just as in a non-shared subscription.

Unsubscribing is done by passing the same value to the [Unsubscribe](#unsubscribe-method-mqtt-component) method.

A shared subscription behaves the same way as a non-shared subscription, except that the *$share/{ShareName}* portion of the topic filter is ignored when filtering publication topics, and that the server will distribute delivery of messages amongst the group, with each message delivered to only one client per group per topic.

Shared subscriptions can be implemented without any additional properties or methods, simply by using the Subscribe and [Unsubscribe](#unsubscribe-method-mqtt-component) methods. However, if it is necessary to verify that the feature is supported by the server, check the "SharedSubscriptionAvailable" value of the [ConnAckProperties](#ConnAckProperties) config.

**Shared Subscription Example**

```csharp
mqtt1.Subscribe("$share/myShareGroup/myTopicFilter/subTopic", 2);
```

### Subscription Options

MQTT 5 defines three subscription options which can be configured on a per-subscription basis and are useful for message bridge applications:

- No Local flag - indicates that messages must not be forwarded to a connection with a [ClientId](#clientid-property-mqtt-component) equal to the [ClientId](#clientid-property-mqtt-component) of the publishing connection (cannot be set on a shared subscription).
- Retain As Published flag - indicates that messages forwarded using this subscription keep the retain flag they were published with (as opposed to always being set to *False*).
- Retain Handling option - specifies whether retained messages are sent when the subscription is established. Possible values are:

|  |  |
| --- | --- |
| 0 | Send retained messages at the time of the subscribe |
| 1 | Send retained messages at subscribe only if the subscription does not currently exist |
| 2 | Do not send retained messages at the time of the subscribe |

To specify these options in the subscribe method, the component has three corresponding configuration settings ([TopicNLArray](#TopicNLArray), [TopicRAPArray](#TopicRAPArray) and [TopicRHArray](#TopicRHArray)) which each take a string value in the form of a comma-separated list. Each element in the list corresponds to a topic filter passed to the Subscribe method, as with [TopicQOSArray](#TopicQOSArray).

If the subscription is only for one topic, these lists would have only one value. If the number of elements in the string is less than the number of topic filters in the subscription, the final element will be applied to all remaining topics.

**Subscription Options Example**

```csharp
mqtt1.Connected = true;
mqtt1.Config("TopicNLArray=true, false, true"); // TestTopic1 = true, TestTopic2 = false, TestTopic3 = true
mqtt1.Config("TopicRAPArray=false"); // TestTopic1 = false, TestTopic2 = false, TestTopic3 = false
mqtt1.Config("TopicRHArray=1, 0"); // // TestTopic1 = 1, TestTopic2 = 0, TestTopic3 = 0
mqtt1.Subscribe("TestTopic1, TestTopic2, TestTopic3", 1);
```

### Subscription Identifiers

MQTT 5 allows clients to specify a numeric subscription identifier which will be returned with messages delivered for that subscription.

To do so with the component, set the [SubscriptionIdentifier](#SubscriptionIdentifier) configuration setting before calling Subscribe. To update the identifier, call Subscribe with a new [SubscriptionIdentifier](#SubscriptionIdentifier).

To verify that a server supports subscription identifiers, check the "SubscriptionIdentifiersAvailable" value in the [ConnAckProperties](#ConnAckProperties) configuration setting. See the SubscriptionIdentifiers property of the MQTTMessage type for details on returning the ids associated with messages.

Note that a topic may have multiple identifiers associated with it (due to wildcards), and the same identifier may be associated with multiple topics.

**Subscription Options Example**

```csharp
mqtt1.Connected = true;
mqtt1.OnMessageAck += (o, e) => {
  String ids = mqtt1.IncomingMessages[e.Index].SubscriptionIdentifiers; // ids = "123,321"
};

mqtt1.Config("SubscriptionIdentifier=123");
mqtt1.Subscribe("test_topic/subtopic", 1);
mqtt1.Config("SubscriptionIdentifier=321");
mqtt1.Subscribe("test_topic/+", 1);

mqtt2.Connected = true;
mqtt2.PublishMessage("test_topic/subtopic", 1, "hello world");
```

# Unsubscribe Method ([MQTT](#mqtt-component) Component)

Unsubscribes the component from one or more topic filters.

## Syntax

*C++ Builder Syntax*

```text
void __fastcall Unsubscribe(String TopicFilter);
```

## Remarks

This method unsubscribes the component from one or more topic filters. The string passed for *TopicFilter* must contain one or more valid topic filter strings, separated by the delimiter string specified by the [TopicDelimiter](#TopicDelimiter) configuration setting (*,* by default).

The [Unsubscribed](#unsubscribed-event-mqtt-component) event will fire when the server has acknowledged the unsubscribe request. However, note that the server's acknowledgment *doesn't* specify which topics a client was unsubscribed from. Please refer to the [Unsubscribed](#unsubscribed-event-mqtt-component) event for more information.

To successfully unsubscribe from a topic filter, the exact filter must be passed to Unsubscribe, regardless of whether or not if contains wildcards. The server ignores any topic filters in an unsubscribe request which do not exactly match that of an existing subscription.

It is impossible to partially unsubscribe from a topic filter with wildcards (that is, if a client is subscribed to a topic filter *home/floor1/+/#*, requesting to unsubscribe from a topic filter *home/floor1/livingRoom/temperature* does nothing).

Similarly, because topic filters in an unsubscribe request are simply compared character-by-character with existing subscriptions rather than being interpreted, it is not possible to perform an action such as unsubscribing from all currently subscribed topics by passing *"#"* for *TopicFilter*.

**Unsubscribe Example**

```csharp
// Unsubscribe from topic filters; have to use the exact same strings as before. If this
// was to be called after calling the code example shown for the Subscribe() method, we
// would still be subscribed to the "home" topic filter.
mqtt1.Unsubscribe("home/floor1/+/temperature,home/floor2/#");
```

# Connected Event ([MQTT](#mqtt-component) Component)

Fired immediately after a connection completes (or fails).

## Syntax

*C++ Builder Syntax*

```text
typedef struct {
  int StatusCode;
  String Description;
} TiotMQTTConnectedEventParams;
typedef void __fastcall (__closure *TiotMQTTConnectedEvent)(System::TObject* Sender, TiotMQTTConnectedEventParams *e);
__property TiotMQTTConnectedEvent OnConnected = { read=FOnConnected, write=FOnConnected };
```

## Remarks

If the connection is made normally, *StatusCode* is 0 and *Description* is "OK".

If the connection fails, *StatusCode* has the error code returned by the Transmission Control Protocol (TCP)/IP stack. *Description* contains a description of this code. The value of *StatusCode* is equal to the value of the error.

Please refer to the [Error Codes](#trappable-errors-mqtt-component) section for more information.

# ConnectionStatus Event ([MQTT](#mqtt-component) Component)

Fired to indicate changes in the connection state.

## Syntax

*C++ Builder Syntax*

```text
typedef struct {
  String ConnectionEvent;
  int StatusCode;
  String Description;
} TiotMQTTConnectionStatusEventParams;
typedef void __fastcall (__closure *TiotMQTTConnectionStatusEvent)(System::TObject* Sender, TiotMQTTConnectionStatusEventParams *e);
__property TiotMQTTConnectionStatusEvent OnConnectionStatus = { read=FOnConnectionStatus, write=FOnConnectionStatus };
```

## Remarks

This event is fired when the connection state changes: for example, completion of a firewall or proxy connection or completion of a security handshake.

The *ConnectionEvent* parameter indicates the type of connection event. Values may include the following:

|  |  |
| --- | --- |
|  | Firewall connection complete. |
|  | Secure Sockets Layer (SSL) or S/Shell handshake complete (where applicable). |
|  | Remote host connection complete. |
|  | Remote host disconnected. |
|  | SSL or S/Shell connection broken. |
|  | Firewall host disconnected. |

 *StatusCode* has the error code returned by the Transmission Control Protocol (TCP)/IP stack. *Description* contains a description of this code. The value of *StatusCode* is equal to the value of the error.

# Disconnected Event ([MQTT](#mqtt-component) Component)

Fired when a connection is closed.

## Syntax

*C++ Builder Syntax*

```text
typedef struct {
  int StatusCode;
  String Description;
} TiotMQTTDisconnectedEventParams;
typedef void __fastcall (__closure *TiotMQTTDisconnectedEvent)(System::TObject* Sender, TiotMQTTDisconnectedEventParams *e);
__property TiotMQTTDisconnectedEvent OnDisconnected = { read=FOnDisconnected, write=FOnDisconnected };
```

## Remarks

If the connection is broken normally, *StatusCode* is 0 and *Description* is "OK".

If the connection is broken for any other reason, *StatusCode* has the error code returned by the Transmission Control Protocol (TCP/IP) subsystem. *Description* contains a description of this code. The value of *StatusCode* is equal to the value of the TCP/IP error.

Please refer to the [Error Codes](#trappable-errors-mqtt-component) section for more information.

# Error Event ([MQTT](#mqtt-component) Component)

Fired when information is available about errors during data delivery.

## Syntax

*C++ Builder Syntax*

```text
typedef struct {
  int ErrorCode;
  String Description;
} TiotMQTTErrorEventParams;
typedef void __fastcall (__closure *TiotMQTTErrorEvent)(System::TObject* Sender, TiotMQTTErrorEventParams *e);
__property TiotMQTTErrorEvent OnError = { read=FOnError, write=FOnError };
```

## Remarks

The Error event is fired in case of exceptional conditions during message processing. Normally the component raises an exception.

The *ErrorCode* parameter contains an error code, and the *Description* parameter contains a textual description of the error. For a list of valid error codes and their descriptions, please refer to the [Error Codes](#trappable-errors-mqtt-component) section.

# Log Event ([MQTT](#mqtt-component) Component)

Fires once for each log message.

## Syntax

*C++ Builder Syntax*

```text
typedef struct {
  int LogLevel;
  String Message;
  String LogType;
} TiotMQTTLogEventParams;
typedef void __fastcall (__closure *TiotMQTTLogEvent)(System::TObject* Sender, TiotMQTTLogEventParams *e);
__property TiotMQTTLogEvent OnLog = { read=FOnLog, write=FOnLog };
```

## Remarks

This event fires once for each log message generated by the component. The verbosity is controlled by the [LogLevel](#LogLevel) setting.

*LogLevel* indicates the level of the *Message*. Possible values are:

|  |  |
| --- | --- |
| 0 (None) | No events are logged. |
| 1 (Info - default) | Informational events are logged. |
| 2 (Verbose) | Detailed data is logged. |
| 3 (Debug) | Debug data is logged. |

*LogType* identifies the type of log entry. Possible values are:

- Info: General information about the component.
- Packet: Packet content logging.
- Reconnect: Reconnection status messages.
- Session: Session status messages.

# MessageAck Event ([MQTT](#mqtt-component) Component)

Fired when an incoming or outgoing message has completed all acknowledgment steps.

## Syntax

*C++ Builder Syntax*

```text
typedef struct {
  int PacketId;
  int Direction;
  int Index;
  int ResponseCode;
} TiotMQTTMessageAckEventParams;
typedef void __fastcall (__closure *TiotMQTTMessageAckEvent)(System::TObject* Sender, TiotMQTTMessageAckEventParams *e);
__property TiotMQTTMessageAckEvent OnMessageAck = { read=FOnMessageAck, write=FOnMessageAck };
```

## Remarks

The MessageAck event fires once an incoming or outgoing message with a QoS of 1 or 2 has successfully completed all acknowledgment steps as required by its QoS level. (Note that this event does not fire for messages with a QoS of 0 since they do not require acknowledgment.)

- *PacketId*: The Id of the original PUBLISH packet for the message.
- *Direction*: Shows whether the client (0) or the server (1) is sending the data.
- *Index*: The index at which the message resides in either the IncomingMessages collection or OutgoingMessages collection.
- *ResponseCode*: In MQTT 5, all response packets contain Reason Codes. This argument contains any code encountered in message acknowledgment packets (PUBACK, PUBREC, PUBREL, PUBCOMP).

Possible MQTT-specific values for *ResponseCode* are:

| Value | Applicable packets | Description |
| --- | --- | --- |
| 0 | PUBACK, PUBREC, PUBREL, PUBCOMP | Success |
| 16 | PUBACK, PUBREC | No matching subscribers |
| 128 | PUBACK, PUBREC | Unspecified error |
| 131 | PUBACK, PUBREC | Implementation specific error |
| 135 | PUBACK, PUBREC | Not authorized |
| 144 | PUBACK, PUBREC | Topic Name invalid |
| 145 | PUBACK, PUBREC | Packet Identifier in use |
| 146 | PUBREL, PUBCOMP | Packet Identifier not found |

### Inbound Message Processing

Incoming messages with a QoS of 1 follow these steps:

1. The message is added to IncomingMessages when the component receives the PUBLISH packet.
2. The component sends a PUBACK (publish acknowledgment) packet in response.
3. The MessageAck event is fired.
4. The message is removed from IncomingMessages.
5. The [MessageIn](#messagein-event-mqtt-component) event is fired.

Incoming messages with a QoS of 2 follow these steps:

1. The message is added to IncomingMessages when the component receives the PUBLISH packet.
2. The component sends a PUBREC (publish received) packet in response.
3. The component waits to receive a PUBREL (publish release) packet.
4. The component sends a PUBCOMP (publish complete) packet in response.
5. The MessageAck event is fired.
6. The message is removed from IncomingMessages.
7. The [MessageIn](#messagein-event-mqtt-component) event is fired.

### Outbound Message Processing

Outgoing messages with a QoS of 1 follow these steps:

1. The component sends the PUBLISH packet, then adds the message to OutgoingMessages.
2. The component waits to receive a PUBACK (publish acknowledgment) packet.
3. The MessageAck event is fired.
4. The message is removed from OutgoingMessages.
5. The [MessageOut](#messageout-event-mqtt-component) event is fired.

Outgoing messages with a QoS of 2 follow these steps:

1. The component sends the PUBLISH packet, then adds the message to OutgoingMessages.
2. The component waits to receive a PUBREC (publish received) packet.
3. The component sends a PUBREL (publish release) packet in response.
4. The component waits to receive a PUBCOMP (publish complete) packet.
5. The MessageAck event is fired.
6. The message is removed from OutgoingMessages.
7. The [MessageOut](#messageout-event-mqtt-component) event is fired.

In MQTT 3.1.1, the [RepublishInterval](#RepublishInterval) configuration setting, if set to a non-zero value (default), controls how long the component will wait to receive a PUBACK (for QoS 1) or PUBREC (for QoS 2) before automatically republishing an outgoing message. In MQTT 5, messages are only republished if the client is disconnected before receiving a PUBACK or PUBREC.

# MessageIn Event ([MQTT](#mqtt-component) Component)

Fired when an incoming message has been received and/or fully acknowledged.

## Syntax

*C++ Builder Syntax*

```text
typedef struct {
  int PacketId;
  String Topic;
  int QOS;
  String Message;
  DynamicArray<Byte> MessageB;
  bool Retained;
  bool Duplicate;
} TiotMQTTMessageInEventParams;
typedef void __fastcall (__closure *TiotMQTTMessageInEvent)(System::TObject* Sender, TiotMQTTMessageInEventParams *e);
__property TiotMQTTMessageInEvent OnMessageIn = { read=FOnMessageIn, write=FOnMessageIn };
```

## Remarks

The MessageIn event fires once for each incoming message either immediately after it is received (QoS 0), or after it has been fully acknowledged (QoS 1 and 2).

- *PacketId*: The message packet Id. This will always be -1 if *QOS* is 0.
- *Topic*: The message's topic string.
- *QOS*: The message's QoS level.
- *Message*: The message data.
- *Retained*: Whether or not this message was received as a result of subscribing to a topic.
- *Duplicate*: Whether or not the server has indicated that this message is a duplicate of another message sent previously.

Refer to [MessageAck](#messageack-event-mqtt-component) for more information about QoS 1 and 2 message processing steps.

```csharp
// MessageIn event handler.
mqtt1.OnMessageIn += (s, e) => {
  Console.WriteLine("Received message from topic '" + e.Topic + "' with QoS " + e.QOS + ":");
  Console.WriteLine(e.Message);
};
```

# MessageOut Event ([MQTT](#mqtt-component) Component)

Fired when an outgoing message has been sent and/or fully acknowledged.

## Syntax

*C++ Builder Syntax*

```text
typedef struct {
  int PacketId;
  String Topic;
  int QOS;
  String Message;
  DynamicArray<Byte> MessageB;
  bool Retained;
  bool Duplicate;
} TiotMQTTMessageOutEventParams;
typedef void __fastcall (__closure *TiotMQTTMessageOutEvent)(System::TObject* Sender, TiotMQTTMessageOutEventParams *e);
__property TiotMQTTMessageOutEvent OnMessageOut = { read=FOnMessageOut, write=FOnMessageOut };
```

## Remarks

The MessageOut event fires once for each outgoing message either immediately after it is sent (QoS 0), or after it has been fully acknowledged by the receiver (QoS 1 and 2).

- *PacketId*: The message packet Id. This will always be -1 if *QOS* is 0.
- *Topic*: The message's topic string.
- *QOS*: The message's QoS level.
- *Message*: The message data.
- *Retained*: Whether or not this message was sent with the "Retain" flag set.
- *Duplicate*: Whether or not this message was sent with the "Duplicate" flag set.

Refer to [MessageAck](#messageack-event-mqtt-component) for more information about QoS 1 and 2 message processing steps.

```csharp
// MessageOut event handler.
mqtt1.OnMessageOut += (s, e) => {
  Console.WriteLine("Send message to topic '" + e.Topic + "' with QoS " + e.QOS + ":");
  Console.WriteLine(e.Message);
};
```

# ReadyToSend Event ([MQTT](#mqtt-component) Component)

Fired when the component is ready to send data.

## Syntax

*C++ Builder Syntax*

```text
typedef struct {
} TiotMQTTReadyToSendEventParams;
typedef void __fastcall (__closure *TiotMQTTReadyToSendEvent)(System::TObject* Sender, TiotMQTTReadyToSendEventParams *e);
__property TiotMQTTReadyToSendEvent OnReadyToSend = { read=FOnReadyToSend, write=FOnReadyToSend };
```

## Remarks

The ReadyToSend event indicates that the underlying TCP/IP subsystem is ready to accept data after a call to [PublishData](#publishdata-method-mqtt-component) or [PublishMessage](#publishmessage-method-mqtt-component) fails due to a WOULDBLOCK condition. The event is also fired immediately after a connection to the remote host is established.

# SSLServerAuthentication Event ([MQTT](#mqtt-component) Component)

Fired after the server presents its certificate to the client.

## Syntax

*C++ Builder Syntax*

```text
typedef struct {
  String CertEncoded;
  DynamicArray<Byte> CertEncodedB;
  String CertSubject;
  String CertIssuer;
  String Status;
  bool Accept;
} TiotMQTTSSLServerAuthenticationEventParams;
typedef void __fastcall (__closure *TiotMQTTSSLServerAuthenticationEvent)(System::TObject* Sender, TiotMQTTSSLServerAuthenticationEventParams *e);
__property TiotMQTTSSLServerAuthenticationEvent OnSSLServerAuthentication = { read=FOnSSLServerAuthentication, write=FOnSSLServerAuthentication };
```

## Remarks

During this event, the client can decide whether or not to continue with the connection process. The *Accept* parameter is a recommendation on whether to continue or close the connection. This is just a suggestion: application software must use its own logic to determine whether or not to continue.

 When *Accept* is False, *Status* shows why the verification failed (otherwise, *Status* contains the string *OK*). If it is decided to continue, you can override and accept the certificate by setting the *Accept* parameter to True.

# SSLStatus Event ([MQTT](#mqtt-component) Component)

Fired when secure connection progress messages are available.

## Syntax

*C++ Builder Syntax*

```text
typedef struct {
  String Message;
} TiotMQTTSSLStatusEventParams;
typedef void __fastcall (__closure *TiotMQTTSSLStatusEvent)(System::TObject* Sender, TiotMQTTSSLStatusEventParams *e);
__property TiotMQTTSSLStatusEvent OnSSLStatus = { read=FOnSSLStatus, write=FOnSSLStatus };
```

## Remarks

The event is fired for informational and logging purposes only. This event tracks the progress of the connection.

# Subscribed Event ([MQTT](#mqtt-component) Component)

Fires for each topic filter subscription the server acknowledges.

## Syntax

*C++ Builder Syntax*

```text
typedef struct {
  String TopicFilter;
  int QOS;
  int ResponseCode;
} TiotMQTTSubscribedEventParams;
typedef void __fastcall (__closure *TiotMQTTSubscribedEvent)(System::TObject* Sender, TiotMQTTSubscribedEventParams *e);
__property TiotMQTTSubscribedEvent OnSubscribed = { read=FOnSubscribed, write=FOnSubscribed };
```

## Remarks

This event fires each time the server has acknowledged a topic filter subscription request (that is, calling [Subscribe](#subscribe-method-mqtt-component) with multiple topic filters will cause this to fire multiple times).

- *TopicFilter*: The topic filter subscription request being acknowledged.
- *QOS*: The QoS level the server has granted for the subscription.
- *ResponseCode*: Indicates the result of the subscription request.

Possible values for *ResponseCode* are:

- *0*: Success, QoS 0 granted
- *1*: Success, QoS 1 granted
- *2*: Success, QoS 2 granted
- *128*: Unspecified error
- *131*: Implementation specific error; The SUBSCRIBE is valid but the Server does not accept it.
- *135*: Not authorized; The Client is not authorized to make this subscription.
- *143*: Topic Filter invalid; The Topic Filter is correctly formed but is not allowed for this Client.
- *145*: Packet Identifier in use
- *151*: Quota exceeded; An implementation or administrative imposed limit has been exceeded.
- *158*: Shared Subscriptions not supported
- *161*: Shared Subscriptions not supported
- *162*: Wildcard Subscriptions not supported

Keep in mind that the server may have chosen to grant a lower QoS than was requested under certain circumstances (e.g., if the server doesn't support the requested QoS).

NOTE: the server is not required to acknowledge a subscription before it begins delivering messages for that subscription.

# Unsubscribed Event ([MQTT](#mqtt-component) Component)

Fires when the server has acknowledged an unsubscribe request.

## Syntax

*C++ Builder Syntax*

```text
typedef struct {
  String TopicFilters;
  int ResponseCode;
} TiotMQTTUnsubscribedEventParams;
typedef void __fastcall (__closure *TiotMQTTUnsubscribedEvent)(System::TObject* Sender, TiotMQTTUnsubscribedEventParams *e);
__property TiotMQTTUnsubscribedEvent OnUnsubscribed = { read=FOnUnsubscribed, write=FOnUnsubscribed };
```

## Remarks

This event fires when the server has acknowledged an unsubscribe request sent with [Unsubscribe](#unsubscribe-method-mqtt-component) (that is, unlike the [Subscribed](#subscribed-event-mqtt-component) event, this event fires only once for each call to [Unsubscribe](#unsubscribe-method-mqtt-component), regardless of how many topic filters are passed to it).

Note that in MQTT 3.1.1, servers *do not specify* which topic filters a client has been successfully unsubscribed in their acknowledgments. In fact, they will still acknowledge an unsubscribe request even if *none* of the topic filters included matched existing subscriptions. It is up to the client to keep track of what topics it is subscribed to; the *TopicFilters* parameter is provided as a convenience, its value simply a copy of the value passed to [Unsubscribe](#unsubscribe-method-mqtt-component) originally.

Possible values for *ResponseCode* are:

- *0*: Success; The subscription is deleted.
- *17*: No subscription existed; No matching Topic Filter is being used by the Client.
- *128*: Unspecified error; The unsubscribe could not be completed and the Server either does not wish to reveal the reason or none of the other Reason Codes apply.
- *131*: Implementation specific error; The UNSUBSCRIBE is valid but the Server does not accept it.
- *135*: Not authorized; The Client is not authorized to unsubscribe.
- *143*: Topic Filter invalid; The Topic Filter is correctly formed but is not allowed for this Client.
- *145*: Packet Identifier in use; The specified Packet Identifier is already in use.

# Config Settings ([MQTT](#mqtt-component) Component)

 The component accepts one or more of the following *configuration settings*. Configuration settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the component, access to these *internal properties* is provided through the [Config](#config-method-mqtt-component) method.

### MQTT Config Settings

**AutoReconnect**: Whether to automatically attempt to reconnect in the event of a connection error.When enabled, the component will automatically attempt to reconnect to the server if the connection is interrupted due to a connection error. This behavior is disabled by default.

**ClientTopicAliasMax**: The maximum value the client will accept for a topic alias sent by the server.The client uses this value to limit the number of aliases it is willing to hold on this connection. A value of *0* (default) indicates that the client does not accept any topic aliases on this connection.

This value is sent to the server in the CONNECT packet and must be set before calling [Connect](#connect-method-mqtt-component). It is also available in the [ConnectProperties](#ConnectProperties) config. See the [TopicAlias](#TopicAlias) config for more details.

Valid only for MQTT 5.

**ConnAckProperties**: JSON string containing the properties returned in the CONNACK packet.This property is set when the component receives the CONNACK packet from the server and describes server-specified requirements and server-supported features.

The values listed below are available. If a value is absent in the CONNACK packet, the client should treat its value as the default listed.

| Name | Type | Default | Description |
| --- | --- | --- | --- |
| AssignedClientIdentifier | String | N/A | The Client Identifier which was assigned by the Server because a zero length Client Identifier was found in the CONNECT packet. |
| MaximumQoS | Integer | 2 | The maximum accepted QoS of PUBLISH packets to be received by the server. |
| MaximumPacketSize | Integer | Unlimited | Maximum packet size in bytes the server is willing to accept. |
| ReasonString | String | N/A | A human readable string designed for diagnostics. |
| ReceiveMaximum | Integer | 65,535 | Number of QoS 1 and QoS 2 publications the server is willing to process concurrently for the client. |
| ResponseInformation | String | N/A | String used as the basis for creating a Response Topic. |
| RetainAvailable | Boolean | True | Indicates whether the client may send PUBLISH packets with [Retain](#Retain) set to True. |
| ServerKeepAlive | Integer | Value in CONNECT | Keep Alive time assigned by server. If specified by server this value overrides the value requested by the client. |
| ServerTopicAliasMax | Integer | 0 | See [ServerTopicAliasMax](#ServerTopicAliasMax). |
| SessionExpInterval | Integer | Value in CONNECT | Defines the length of time for which the client and server must store session state data after disconnection. If included in the CONNACK and different than the [SessionExpInterval](#SessionExpInterval) which the client requested in the CONNECT packet, this value overrides the client-requested value and must be followed by the client. |
| SharedSubscriptionAvailable | Boolean | True | Indicates whether the server supports shared subscriptions. |
| SubscriptionIdentifiersAvailable | Boolean | True | Indicates whether the server supports subscription identifiers. |
| WildcardSubscriptionAvailable | Boolean | True | Indicates whether the server supports wildcard subscriptions. |

Read-only. Valid only for MQTT 5.

**ConnectionTimeout**: How long to wait for a connection attempt to succeed.This setting controls how long the component will wait, in seconds, for connection attempt to succeed before timing out. The default is 60 seconds.

**ConnectProperties**: JSON string specifying properties to be included in the CONNECT packet.The values listed below are available. If a value is absent in the CONNECT packet, the server will treat its value as the default listed.

To reset an individual value so that it is no longer included in the CONNECT packet (after it has previously been set), set it to *""*, or *-1* for integers. To reset all [ConnectProperties](#ConnectProperties) values, set the config JSON string to *""*.

| Name | Type | Default | Description |
| --- | --- | --- | --- |
| ClientTopicAliasMax | Integer | 0 | See [ClientTopicAliasMax](#ClientTopicAliasMax). |
| MaximumPacketSize | Integer | Unlimited | Maximum Packet Size the Client is willing to accept (cannot be 0). |
| ReceiveMaximum | Integer | 65,535 | The number of QoS 1 and QoS 2 publications the client is willing to process concurrently. |
| RequestProblemInformation | Boolean | True | Indicates the server is allowed to return a Reason String and or User Properties on packets other than PUBLISH, CONNACK or DISCONNECT. |
| RequestResponseInformation | Boolean | False | Indicates the client requests the server to return response information in the CONNACK packet. |
| SessionExpInterval | Integer | 0 | See [SessionExpInterval](#SessionExpInterval). |

To set these values, set the [ConnectProperties](#ConnectProperties) config to a string JSON object containing one or more key/value pairs to set. For example, to set all values:

```text
{
  "ClientTopicAliasMax":"20",
  "MaximumPacketSize":"128000",
  "ReceiveMaximum":"12",
  "RequestResponseInformation":"false",
  "RequestProblemInformation":"true",
  "SessionExpInterval":"1234"
}
```

Valid only for MQTT 5.

**DisconnectProperties**: JSON string containing DISCONNECT packet properties.This property contains properties to be sent by the client in the DISCONNECT packet, or is set when the client receives a DISCONNECT packet from the server.

Supported properties are:

| Name | Type | Default | Description |
| --- | --- | --- | --- |
| SessionExpInterval | Integer | Value in CONNECT | Can only be sent by client. A new length of time for the client and server to store session state data. Cannot be non-zero if the client set it to zero in the CONNECT packet. If absent, the client and server should use the value specified in the CONNECT packet. |
| ReasonString | String | N/A | A human readable string designed for diagnostics. |

To reset an individual value so that it is no longer included in the DISCONNECT packet (after it has previously been set), set it to *""*, or *-1* for integers. To reset all [DisconnectProperties](#DisconnectProperties) values, set the config JSON string to *""*.

Valid only for MQTT 5.

**DisconnectReasonCode**: Code describing the reason the client or server closed the connection.Either the client or server may set a reason code before disconnecting to be included in the DISCONNECT packet.

To specify a code as the client, set this value before calling [Disconnect](#disconnect-method-mqtt-component).

This value will be populated when the component receives a DISCONNECT packet from the server.

For a full list of values applicable to be sent by the client, server or both, see the MQTT 5 specification. They include:

- *0x00*: Normal disconnection - Close the connection normally. Do not send the Will Message.
- *0x04*: Disconnect with Will Message (Client only) - The Client wishes to disconnect but requires that the Server also publishes its Will Message.
- *0x80*: Unspecified error - The Connection is closed but the sender either does not wish to reveal the reason, or none of the other Reason Codes apply.

Valid only for MQTT 5.

**Duplicate**: Whether to set the Duplicate flag when publishing a message.When enabled, the component will set the Duplicate flag when a message is published using [PublishData](#publishdata-method-mqtt-component) or [PublishMessage](#publishmessage-method-mqtt-component). By default, this is disabled; and manually enabling it is not recommended. Prefer instead to let the component handle republishing packets, which it will do automatically so long as [RepublishInterval](#RepublishInterval) is set to a non-zero value (default).

This setting is ignored when messages are published with a QoS of 0.

NOTE: The Duplicate flag in an MQTT PUBLISH packet refers to the Id of the packet, *not* the message itself. According to the MQTT specification, it is possible (and perfectly legal) that a client could receive two QoS 1 PUBLISH packets with different Ids despite having the exact same message data.

**IncomingUserPropCount**: The size of the IncomingUserPropName and IncomingUserPropValue arrays.This setting can be queried to return the number of distinct user properties in the previous received message.

Read-only. Valid only for MQTT 5.

**IncomingUserPropName[i]**: The name of the user property at index i.This setting can be queried to return the name of a specific user property.

Read-only. Valid only for MQTT 5.

**IncomingUserPropValue[i]**: The value of the user property at index i.This setting can be queried to return the value of a specific user property.

Read-only. Valid only for MQTT 5.

**LogLevel**: The level of detail that is logged.This setting controls the level of detail that is logged through the [Log](#log-event-mqtt-component) event. Possible values are:

|  |  |
| --- | --- |
| 0 (None) | No events are logged. |
| 1 (Info - default) | Informational events are logged. |
| 2 (Verbose) | Detailed data is logged. |
| 3 (Debug) | Debug data is logged. |

**OutgoingMessageProperties**: JSON string specifying properties to be included in the PUBLISH packet.The values listed below are available. If a value is absent in the PUBLISH packet, the server will treat its value as the default listed.

To reset an individual value so that it is no longer included in the PUBLISH packet (after it has previously been set), set it to *""*, or *-1* for integers. To reset all [OutgoingMessageProperties](#OutgoingMessageProperties) values, set the config JSON string to *""*.

| Name | Type | Default | Description |
| --- | --- | --- | --- |
| ContentType | String | N/A | String describing content of message to be sent to all subscribers receiving the message. |
| CorrelationData | String | N/A | Hex-encoded binary string used by the sender of a request message to identify which request the response message is for when received (See [ResponseTopic](#ResponseTopic)). |
| MessageExpInterval | Integer | No exp. | Length of time after which the server must stop delivery to a subscriber if not yet processed. |
| PayloadFormatIndicator | Integer | 0x00 | 0x00 = unspecified bytes. 0x01 = UTF-8 encoded character data. Sent to all subscribers receiving the message. |
| ResponseTopic | String | N/A | See [ResponseTopic](#ResponseTopic). |
| TopicAlias | Integer | N/A | See [TopicAlias](#TopicAlias). |
| UserProperty | String | "" | String key:value pair to be included in the header properties. The UserProperty can appear multiple times to represent multiple name, value pairs. |

To set these values, set the [OutgoingMessageProperties](#OutgoingMessageProperties) config to a string JSON object containing one or more key/value pairs to set. For example:

```text
{
  "ContentType":"plain/text",
  "CorrelationData":"00000000",
  "MessageExpInterval":"1000",
  "PayloadFormatIndicator":"1",
  "ResponseTopic": "ResponseTopic",
  "TopicAlias":"1",
  "UserProperty":"prp1:val1",
  "UserProperty":"prp2:val2"
}
```

 Valid only for MQTT 5.

**OutgoingPacketId**: The packet Id of the last message published.This configuration setting can be queried to determine the packet Id of the last message published.

**OutgoingUserPropCount**: Controls the size of the OutgoingUserPropName and OutgoingUserPropValue configuration arrays.Set this to a positive integer to indicate the total number of User Properties which will be specified in OutgoingUserPropName and OutgoingUserPropValue.

By default, this setting is *0* and no User Properties are sent in the outgoing message.

**Code Example**

```text
mqtt1.Connected = true;
mqtt.Config("OutgoingUserPropCount=1");
mqtt.Config("OutgoingUserPropName[0]=prp1");
mqtt.Config("OutgoingUserPropValue[0]=val1");
mqtt1.PublishMessage(topic, 1, "hello");
```

Valid only for MQTT 5.

**OutgoingUserPropName[i]**: The name of the User Property at index i.Each index in the array corresponds to a distinct User Property to include in the outgoing message. This setting controls the name part of the string pair at index i.

The size of this array is controlled by the [OutgoingUserPropCount](#OutgoingUserPropCount) configuration setting.

Valid only for MQTT 5.

**OutgoingUserPropValue[i]**: The value of the User Property at index i.Each index in the array corresponds to a distinct User Property to send in the outgoing message. This setting controls the value part of the string pair at index i.

 The size of this array is controlled by the [OutgoingUserPropCount](#OutgoingUserPropCount) configuration setting.

Valid only for MQTT 5.

**RepublishInterval**: How many seconds to wait before republishing unacknowledged messages.In MQTT 3.1.1 this setting determines how long the component will wait to receive a PUBACK (QoS 1) or PUBREC (QoS 2) for an outgoing message before republishing it. Republished messages will automatically use the same packet Id and have their Duplicate flag set.

The default [RepublishInterval](#RepublishInterval) is 60 seconds. Specify a [RepublishInterval](#RepublishInterval) of 0 to prevent the component from automatically republishing messages.

In MQTT 5, messages are only republished if the client is disconnected before receiving a PUBACK or PUBREC. This property is only valid for MQTT 3.1.1.

**ResponseTopic**: Topic name for a response message.The receiver of a message with a Response Topic sends a response by using the Response Topic as the Topic Name of a PUBLISH. If the Request Message contains a Correlation Data, the receiver of the Request Message should also include this Correlation Data as a property in the PUBLISH packet of the Response Message.

To send a Request Message, set this value before calling [PublishMessage](#publishmessage-method-mqtt-component).

To reset the value once it has been previously set, so that it is no longer included in future packets, set it to *""*.

[ResponseTopic](#ResponseTopic) and Correlation Data are also accessible in the [OutgoingMessageProperties](#OutgoingMessageProperties) config.

Valid only for MQTT 5.

**Retain**: Whether to set the Retain flag when publishing a message.When enabled, the component will set the Retain flag when a message is published using [PublishData](#publishdata-method-mqtt-component) or [PublishMessage](#publishmessage-method-mqtt-component). By default, this is disabled.

Publishing a *non-empty* message with the Retain flag set and a non-zero QoS will cause the server to store it (replacing any previously retained message in the process) so that it can be delivered to any clients which subscribe to the topic in the future. (If the QoS is 0, the server *can* store the message, but it is not *required* to do so indefinitely, if at all.)

If the component publishes an *empty* message with the Retain flag set, then (regardless of its QoS) the server will remove any previously retained message for the topic.

Note that messages with the Retain flag set are still processed by the server and delivered as usual to clients currently subscribed to the topic, regardless of whether they are empty or not. Also note that retained messages are not part of a session's state, they are retained until they are either removed or replaced by another retained message, regardless of whether or not the client connected with [CleanSession](#cleansession-property-mqtt-component) set to *True*.

**MQTT 5 Notes**

In MQTT 5, the "RetainAvailable" value in the [ConnAckProperties](#ConnAckProperties) config indicates whether the client may send messages with the Retain flag set to *True*.

**SendCustomPacket**: Sends a packet constructed using the supplied hex byte string.Setting this setting to a string with hex bytes will cause the component to construct and send a custom packet. This should not be necessary except for debugging purposes.

**ServerTopicAliasMax**: The highest value that the Server will accept as a Topic Alias sent by the Client.The Client must not send topic aliases less than *1* or greater than this value.

This property is also accessible in the [ConnAckProperties](#ConnAckProperties) config.

Read-only. Valid only for MQTT 5.

**SessionExpInterval**: The length of time in seconds the client and server should store session state data after the connection is closed.If *0* (default), the session ends on disconnection. If *0xFFFFFFFF*, the session does not expire.

The server may return a different Session Expiration Interval in the [ConnAckProperties](#ConnAckProperties), overriding this value. Additionally, the client may send a new value in the [DisconnectProperties](#DisconnectProperties) (as long as it was not *0* originally).

See [CleanSession](#cleansession-property-mqtt-component) for more details on stored sessions in MQTT 5. This property also available in [ConnectProperties](#ConnectProperties).

Valid only for MQTT 5.

**SessionPresent**: When connecting with CleanSession disabled, indicates whether the server actually had any previous session data stored.If [CleanSession](#cleansession-property-mqtt-component) is *False* when [Connect](#connect-method-mqtt-component) is called, query this setting after the component connects to determine whether the server *actually* had data from a previous session.

If [CleanSession](#cleansession-property-mqtt-component) is *True* when [Connect](#connect-method-mqtt-component) is called, this will always return *False*.

**SessionStateFile**: File to use for saving and restoring session data.This can be set to a valid file path before calling [SaveSession](#savesession-method-mqtt-component) or [RestoreSession](#restoresession-method-mqtt-component) to have the component automatically save and restore the session state data to and from a file.

**SubscriptionIdentifier**: A numeric subscription identifier included in SUBSCRIBE packet which will be returned with messages delivered for that subscription.To instruct the server to establish a subscription identifier mapping and return this value with any future PUBLISH packets for a topic filter, set this config before calling [Subscribe](#subscribe-method-mqtt-component) for the desired topic.

Note that this value applies only to SUBSCRIBE packets and not to outgoing or incoming messages. The client is not permitted to send a PUBLISH packet with a subscription id - the server will include it when it sends PUBLISH packets to subscribing clients if those clients have established ids. To access subscription ids of incoming messages, see the "SubscriptionIdentifiers" field in the MQTTMessage type.

To reset the value once it has been previously set, so that it is no longer included in future packets, set it to *-1*.

See the [Subscribe](#subscribe-method-mqtt-component) method for details on subscription identifiers. Valid only for MQTT 5.

**TopicAlias**: Value that is used to identify the Topic instead of using the Topic Name in order to reduce packet size.To establish a topic alias mapping, set this to a unique value before calling [PublishMessage](#publishmessage-method-mqtt-component) with the desired topic filter. Then, next time the client publishes a message to this topic, it may set [TopicAlias](#TopicAlias) to the value established and call [PublishMessage](#publishmessage-method-mqtt-component) with an empty topic filter string. The message will be published to the proper topic without sending the topic filter.

A sender can modify the Topic Alias mapping by sending another PUBLISH in the same Network Connection with the same Topic Alias value and a different non-zero length Topic Name.

Note that a topic alias must have a value greater than zero and less than or equal to [ServerTopicAliasMax](#ServerTopicAliasMax). Topic alias mappings exist only within a connection and are not a part of stored session state data. The Topic Alias mappings used by the Client and Server are independent from each other.

To reset the value once it has been previously set, so that it is no longer included in future packets, set it to *-1*.

Also accessible in the [OutgoingMessageProperties](#OutgoingMessageProperties) config.

**Code Example**

```csharp
mqtt1.Connected = true;
mqtt1.Config("TopicAlias=1"); // map 1 to topic "PublishWithTopicAlias"
mqtt1.PublishMessage(topic, 1, "hello");
mqtt1.Config("TopicAlias=1"); // set topic alias 1 to publish with empty topic filter
mqtt1.PublishMessage("", 1, "hello");
```

Valid only for MQTT 5.

**TopicDelimiter**: The string to use as a delimiter in a topic filter list string.When the [Subscribe](#subscribe-method-mqtt-component) and [Unsubscribe](#unsubscribe-method-mqtt-component) methods are called, the component parses the topic filters string passed to them into a list of topic filters by splitting it, using this setting's current value as the delimiter. By default, this is set to *,*.

**TopicNLArray**: List of No Local option flags for subscription topic filters.The value of this config should be a comma-separated list of boolean values.

For topic filters subscribed to with a *True* flag, messages will not be forwarded to the same [ClientId](#clientid-property-mqtt-component) they were published from.

By default, this value is empty and all flags are *False*.

See the [Subscribe](#subscribe-method-mqtt-component) method for more details on Subscription Options. Valid only for MQTT 5.

**TopicQOSArray**: Comma-separated list of topic filter QoS values to use when subscribing.This can be set to a comma-separated list of individual QoS values to use for each topic filter passed to the [Subscribe](#subscribe-method-mqtt-component) method, causing the component to ignore the QoS value passed to [Subscribe](#subscribe-method-mqtt-component). When doing this, the number of QoS values set to this setting must match the number of topic filters passed to [Subscribe](#subscribe-method-mqtt-component).

If this setting is set to the empty string (default) when [Subscribe](#subscribe-method-mqtt-component) is called with multiple topic filters, the component will use the QoS value passed to [Subscribe](#subscribe-method-mqtt-component) for all of them.

**TopicRAPArray**: List of Retain As Published option flags for subscription topic filters.The value of this config should be a comma-separated list of boolean values.

For topic filters subscribed to with a *True* flag, messages forwarded for this subscription will keep the retain flag they were published with (as opposed to always being set to *False*).

By default, this value is empty and all flags are *False*.

See the [Subscribe](#subscribe-method-mqtt-component) method for more details on Subscription Options. Valid only for MQTT 5.

**TopicRHArray**: List of Retain Handling option values for subscription topic filters.The value of this config should be a comma-separated list of integer values specifying whether retained messages are sent when the subscription is established. Possible values are:

- *0* = send retained messages at the time of the subscribe
- *1* = send retained messages at subscribe only if the subscription does not currently exist
- *2* = do not send retained messages at the time of the subscribe

By default, this value is empty and all values are *0*.

See the [Subscribe](#subscribe-method-mqtt-component) method for more details on Subscription Options. Valid only for MQTT 5.

**WillProperties**: JSON string specifying will properties to be included in the CONNECT packet.The values listed below are available. If a value is absent in the CONNECT packet, the server will treat its value as the default listed.

To reset an individual value so that it is no longer included in the CONNECT packet (after it has previously been set), set it to *""*, or *-1* for integers. To reset all [WillProperties](#WillProperties) values, set the config JSON string to *""*.

| Name | Type | Default | Description |
| --- | --- | --- | --- |
| ContentType | String | N/A | String describing content of will message. |
| CorrelationData | String | N/A | Hex-encoded binary string used by the sender of a request message to identify which request the response message is for when received. |
| MessageExpInterval | Integer | No exp. | Length of time after which the server must stop delivery of the will message to a subscriber if not yet processed. |
| PayloadFormatIndicator | Integer | 0x00 | 0x00 = unspecified bytes. |
| ResponseTopic | String | N/A | Used as a topic name for a response message. |
| WillDelayInterval | Integer | 0 | Delay in seconds after disconnection until the server should publish the client [WillMessage](#willmessage-property-mqtt-component). |

Note that these values will be ignored if [WillTopic](#willtopic-property-mqtt-component) is empty.

To set these values, set the [ConnectProperties](#ConnectProperties) config to a string JSON object containing one or more key/value pairs to set. For example, to set all values:

```text
{
"ContentType":"text/plain",
"CorrelationData":"00000000",
"MessageExpInterval":"3600",
"PayloadFormatIndicator":"1",
"ResponseTopic": "ResponseTopic",
"WillDelayInterval":"10"
}
```

Valid only for MQTT 5.

**WillQOS**: The QoS value to use for the Will message.If [WillTopic](#willtopic-property-mqtt-component) is set to a non-empty string when [Connect](#connect-method-mqtt-component) is called, this is the QoS value that will be used for the Will message; possible values are 0 (default), 1, and 2. (Note that this setting is ignored if [WillTopic](#willtopic-property-mqtt-component) is empty.)

Refer to [WillTopic](#willtopic-property-mqtt-component) for more information.

**WillRetain**: Whether the server should retain the Will message after publishing it.If [WillTopic](#willtopic-property-mqtt-component) is set to a non-empty string when [Connect](#connect-method-mqtt-component) is called, this determines whether or not the server will treat the Will message as retained. By default, this is disabled. (Note that this setting is ignored if [WillTopic](#willtopic-property-mqtt-component) is empty.)

See [Retain](#Retain) for general information about how retained messages are handled by the server.

Refer to [WillTopic](#willtopic-property-mqtt-component) for more information.

### TCPClient Config Settings

**ConnectionTimeout**: Sets a separate timeout value for establishing a connection.When set, this configuration setting allows you to specify a different timeout value for establishing a connection. Otherwise, the component will use [Timeout](#timeout-property-mqtt-component) for establishing a connection and transmitting/receiving data.

**EnableFallback**: Whether to try the other addresses the remote host resolves to when a connection attempt fails.When set to True and [RemoteHost](#remotehost-property-mqtt-component) resolves to more than one address, the component will try the remaining addresses in turn if the connection to the first one fails, and only raises an exception once every address has been tried. The error reported is the one from the last attempt. Use [FallbackTimeout](#FallbackTimeout) to limit the total time spent.

NOTE: Only addresses of the same IP version as the first one are tried, this setting does not fall back from IPv6 to IPv4. Selecting between IPv6 and IPv4 is done by [UseIPv6](#UseIPv6) when the host is resolved.

This setting must be set before the connection is established. The default value for this setting is False.

**FallbackTimeout**: The maximum time in milliseconds to spend on connection attempts when EnableFallback is enabled.This setting limits the total time that the component will spend on all of the connection attempts made when [EnableFallback](#EnableFallback) is enabled. The default value is 0, in which case each attempt uses the operating system's own connection timeout.

NOTE: This setting only applies when [EnableFallback](#EnableFallback) is True. It is unrelated to [ConnectionTimeout](#ConnectionTimeout), which is specified in seconds and applies to the [Connected](#connected-property-mqtt-component) operation as a whole.

**FirewallAutoDetect**: Tells the component whether or not to automatically detect and use firewall system settings, if available.This configuration setting is provided for use by components that do not directly expose Firewall properties.

**FirewallHost**: Name or IP address of firewall (optional).If a [FirewallHost](#FirewallHost) is given, requested connections will be authenticated through the specified firewall when connecting.

If the [FirewallHost](#FirewallHost) setting is set to a Domain Name, a DNS request is initiated. Upon successful termination of the request, the [FirewallHost](#FirewallHost) setting is set to the corresponding address. If the search is not successful, an error is returned.

NOTE: This setting is provided for use by components that do not directly expose Firewall properties.

**FirewallHTTPVersion**: The HTTP version to be used when connecting through a tunneling proxy.When [FirewallType](#FirewallType) is set to a tunneling proxy, this setting dictates which HTTP version is used when connecting.

**FirewallPassword**: Password to be used if authentication is to be used when connecting through the firewall.If [FirewallHost](#FirewallHost) is specified, the [FirewallUser](#FirewallUser) and [FirewallPassword](#FirewallPassword) settings are used to connect and authenticate to the given firewall. If the authentication fails, the component raises an exception.

NOTE: This setting is provided for use by components that do not directly expose Firewall properties.

**FirewallPort**: The TCP port for the FirewallHost;.The [FirewallPort](#FirewallPort) is set automatically when [FirewallType](#FirewallType) is set to a valid value.

NOTE: This configuration setting is provided for use by components that do not directly expose Firewall properties.

**FirewallType**: Determines the type of firewall to connect through.Possible values are as follows:

|  |  |
| --- | --- |
| 0 | No firewall (default setting). |
| 1 | Connect through a tunneling proxy. [FirewallPort](#FirewallPort) is set to 80. |
| 2 | Connect through a SOCKS4 Proxy. [FirewallPort](#FirewallPort) is set to 1080. |
| 3 | Connect through a SOCKS5 Proxy. [FirewallPort](#FirewallPort) is set to 1080. |
| 10 | Connect through a SOCKS4A Proxy. [FirewallPort](#FirewallPort) is set to 1080. |

NOTE: This setting is provided for use by components that do not directly expose Firewall properties.

**FirewallUser**: A user name if authentication is to be used connecting through a firewall.If the [FirewallHost](#FirewallHost) is specified, the [FirewallUser](#FirewallUser) and [FirewallPassword](#FirewallPassword) settings are used to connect and authenticate to the Firewall. If the authentication fails, the component raises an exception.

NOTE: This setting is provided for use by components that do not directly expose Firewall properties.

**KeepAliveInterval**: The retry interval, in milliseconds, to be used when a TCP keep-alive packet is sent and no response is received.When set, [TCPKeepAlive](#TCPKeepAlive) will automatically be set to True. A TCP keep-alive packet will be sent after a period of inactivity as defined by [KeepAliveTime](#KeepAliveTime). If no acknowledgment is received from the remote host, the keep-alive packet will be sent again. This configuration setting specifies the interval at which the successive keep-alive packets are sent in milliseconds. This system default if this value is not specified here is 1 second.

NOTE: This value is not applicable in macOS.

**KeepAliveTime**: The inactivity time in milliseconds before a TCP keep-alive packet is sent.When set, [TCPKeepAlive](#TCPKeepAlive) will automatically be set to True. By default, the operating system will determine the time a connection is idle before a Transmission Control Protocol (TCP) keep-alive packet is sent. This system default if this value is not specified here is 2 hours. In many cases, a shorter interval is more useful. Set this value to the desired interval in milliseconds.

**Linger**: When set to True, connections are terminated gracefully.This property controls how a connection is closed. The default is True.

In the case that Linger is True (default), two scenarios determine how long the connection will linger. In the first, if [LingerTime](#LingerTime) is 0 (default), the system will attempt to send pending data for a connection until the default IP timeout expires.

In the second scenario, if [LingerTime](#LingerTime) is a positive value, the system will attempt to send pending data until the specified [LingerTime](#LingerTime) is reached. If this attempt fails, then the system will reset the connection.

The default behavior (which is also the default mode for stream sockets) might result in a long delay in closing the connection. Although the component returns control immediately, the system could hold system resources until all pending data are sent (even after your application closes).

Setting this property to False forces an immediate disconnection. If you know that the other side has received all the data you sent (e.g., by a client acknowledgment), setting this property to False might be the appropriate course of action.

**LingerTime**: Time in seconds to have the connection linger. LingerTime is the time, in seconds, the socket connection will linger. This value is 0 by default, which means it will use the default IP timeout.

**LocalHost**: The name of the local host through which connections are initiated or accepted. The [LocalHost](#localhost-property-mqtt-component) setting contains the name of the local host as obtained by the *gethostname()* system call, or if the user has assigned an IP address, the value of that address.

In multihomed hosts (machines with more than one IP interface), setting LocalHost to the value of an interface will make the component initiate connections (or accept in the case of server components) only through that interface.

If the component is connected, the [LocalHost](#localhost-property-mqtt-component) setting shows the IP address of the interface through which the connection is made in internet dotted format (aaa.bbb.ccc.ddd). In most cases, this is the address of the local host, except for multihomed hosts (machines with more than one IP interface).

**LocalPort**: The port in the local host where the component binds. This configuration setting must be set before a connection is attempted. It instructs the component to bind to a specific port (or communication endpoint) in the local machine.

Setting this to 0 (default) enables the system to choose a port at random. The chosen port will be shown by [LocalPort](#localport-property-mqtt-component) after the connection is established.

[LocalPort](#localport-property-mqtt-component) cannot be changed once a connection is made. Any attempt to set this when a connection is active will generate an error.

This configuration setting is useful when trying to connect to services that require a trusted port on the client side. An example is the remote shell (rsh) service in UNIX systems.

**MaxLineLength**: The maximum amount of data to accumulate when no EOL is found.[MaxLineLength](#MaxLineLength) is the size of an internal buffer, which holds received data while waiting for an EOL string.

If an EOL string is found in the input stream before [MaxLineLength](#MaxLineLength) bytes are received, the DataIn event is fired with the *EOL* parameter set to True, and the buffer is reset.

If no EOL is found, and [MaxLineLength](#MaxLineLength) bytes are accumulated in the buffer, the DataIn event is fired with the *EOL* parameter set to False, and the buffer is reset.

The minimum value for [MaxLineLength](#MaxLineLength) is 256 bytes. The default value is 2048 bytes.

**MaxTransferRate**: The transfer rate limit in bytes per second.This configuration setting can be used to throttle outbound TCP traffic. Set this to the number of bytes to be sent per second. By default, this is not set and there is no limit.

**ProxyExceptionsList**: A semicolon separated list of hosts and IPs to bypass when using a proxy.This configuration setting optionally specifies a semicolon-separated list of hostnames or IP addresses to bypass when a proxy is in use. When requests are made to hosts specified in this property, the proxy will not be used. For instance:

*www.google.com;www.example.com*

**TCPKeepAlive**: Determines whether or not the keep alive socket option is enabled.If set to True, the socket's keep-alive option is enabled and keep-alive packets will be sent periodically to maintain the connection. Set [KeepAliveTime](#KeepAliveTime) and [KeepAliveInterval](#KeepAliveInterval) to configure the timing of the keep-alive packets.

NOTE: This value is not applicable in Java.

**TcpNoDelay**: Whether or not to delay when sending packets. When set to True, the socket will send all data that are ready to send at once. When set to False, the socket will send smaller buffered packets of data at small intervals. This is known as the Nagle algorithm.

By default, this configuration setting is set to False.

**UseIPv6**: Whether to use IPv6.When set to *0* (default), the component will use IPv4 exclusively. When set to *1*, the component will use IPv6 exclusively. To instruct the component to prefer IPv6 addresses, but use IPv4 if IPv6 is not supported on the system, this setting should be set to *2*. The default value is *0*. Possible values are as follows:

|  |  |
| --- | --- |
| 0 | IPv4 only |
| 1 | IPv6 only |
| 2 | IPv6 with IPv4 fallback |

**UseNTLMv2**: Whether to use NTLM V2.When authenticating with NTLM, this setting specifies whether NTLM V2 is used. By default this value is True and NTLM V2 will be used. Set this to False to use NTLM V1.

### SSL Config Settings

**LogSSLPackets**: Controls whether SSL packets are logged when using the internal security API.When [SSLProvider](#sslprovider-property-mqtt-component) is set to *Internal*, this configuration setting controls whether Secure Sockets Layer (SSL) packets should be logged. By default, this configuration setting is *False*, as it is useful only for debugging purposes.

When enabled, SSL packet logs are output using the [SSLStatus](#sslstatus-event-mqtt-component) event, which will fire each time an SSL packet is sent or received.

Enabling this configuration setting has no effect if [SSLProvider](#sslprovider-property-mqtt-component) is set to *Platform*.

**OpenSSLCADir**: The path to a directory containing CA certificates.This functionality is available only when the provider is OpenSSL.

The path set by this property should point to a directory containing CA certificates in PEM format. The files each contain one CA certificate. The files are looked up by the CA subject name hash value, which must hence be available. If more than one CA certificate with the same name hash value exist, the extension must be different (e.g., 9d66eef0.0, 9d66eef0.1). OpenSSL recommends the use of the c_rehash utility to create the necessary links. Please refer to the OpenSSL man page SSL_CTX_load_verify_locations(3) for details.

**OpenSSLCAFile**: Name of the file containing the list of CA's trusted by your application.This functionality is available only when the provider is OpenSSL.

The file set by this property should contain a list of CA certificates in PEM format. The file can contain several CA certificates identified by the following sequences:

 -----BEGIN CERTIFICATE-----

 ... (CA certificate in base64 encoding) ...

 -----END CERTIFICATE-----

 Before, between, and after the certificate text is allowed, which can be used, for example, for descriptions of the certificates. Refer to the OpenSSL man page SSL_CTX_load_verify_locations(3) for details.

**OpenSSLCipherList**: A string that controls the ciphers to be used by SSL.This functionality is available only when the provider is OpenSSL.

The format of this string is described in the OpenSSL man page ciphers(1) section "CIPHER LIST FORMAT". Please refer to it for details. The default string "DEFAULT" is determined at compile time and is normally equivalent to "ALL:!ADH:RC4+RSA:+SSLv2:@STRENGTH".

**OpenSSLPrngSeedData**: The data to seed the pseudo random number generator (PRNG).This functionality is available only when the provider is OpenSSL.

By default, OpenSSL uses the device file "/dev/urandom" to seed the PRNG, and setting OpenSSLPrngSeedData is not required. If set, the string specified is used to seed the PRNG.

**ReuseSSLSession**: Determines if the SSL session is reused.

If set to True, the component will reuse the context if and only if the following criteria are met:

- The target host name is the same.
- The system cache entry has not expired (default timeout is 10 hours).
- The application process that calls the function is the same.
- The logon session is the same.
- The instance of the component is the same.

**SSLCACerts**: A newline separated list of CA certificates to be included when performing an SSL handshake.When [SSLProvider](#sslprovider-property-mqtt-component) is set to *Internal*, this configuration setting specifies one or more CA certificates to be included with the SSLCert property. Some servers or clients require the entire chain, including CA certificates, to be presented when performing SSL authentication. The value of this configuration setting is a newline-separated (CR/LF) list of certificates. For instance:

```text
-----BEGIN CERTIFICATE-----
MIIEKzCCAxOgAwIBAgIRANTET4LIkxdH6P+CFIiHvTowDQYJKoZIhvcNAQELBQAw
... Intermediate Cert ...
eWHV5OW1K53o/atv59sOiW5K3crjFhsBOd5Q+cJJnU+SWinPKtANXMht+EDvYY2w
F0I1XhM+pKj7FjDr+XNj
-----END CERTIFICATE-----
\r \n
-----BEGIN CERTIFICATE-----
MIIEFjCCAv6gAwIBAgIQetu1SMxpnENAnnOz1P+PtTANBgkqhkiG9w0BAQUFADBp
... Root Cert ...
d8q23djXZbVYiIfE9ebr4g3152BlVCHZ2GyPdjhIuLeH21VbT/dyEHHA
-----END CERTIFICATE-----
```

**SSLCheckCRL**: Whether to check the Certificate Revocation List for the server certificate.This configuration setting specifies whether the component will check the Certificate Revocation List (CRL) specified by the server certificate. If set to 1 or 2, the component will first obtain the list of CRL URLs from the server certificate's CRL distribution points extension. The component will then make HTTP requests to each CRL endpoint to check the validity of the server's certificate. If the certificate has been revoked or any other issues are found during validation the component raises an exception.

When set to 0 (default), the CRL check will not be performed by the component. When set to 1, it will attempt to perform the CRL check, but it will continue without an error if the server's certificate does not support CRL. When set to 2, it will perform the CRL check and will throw an error if CRL is not supported.

This configuration setting is supported only in the Java, C#, and C++ editions. In the C++ edition, it is supported only on Windows operating systems.

**SSLCheckOCSP**: Whether to use OCSP to check the status of the server certificate.This configuration setting specifies whether the component will use OCSP to check the validity of the server certificate. If set to 1 or 2, the component will first obtain the Online Certificate Status Protocol (OCSP) URL from the server certificate's OCSP extension. The component will then locate the issuing certificate and make an HTTP request to the OCSP endpoint to check the validity of the server's certificate. If the certificate has been revoked or any other issues are found during validation, the component raises an exception.

When set to 0 (default), the component will not perform an OCSP check. When set to 1, it will attempt to perform the OCSP check, but it will continue without an error if the server's certificate does not support OCSP. When set to 2, it will perform the OCSP check and will throw an error if OCSP is not supported.

This configuration setting is supported only in the Java, C#, and C++ editions. In the C++ edition, it is supported only on Windows operating systems.

**SSLCipherStrength**: The minimum cipher strength used for bulk encryption. This minimum cipher strength is largely dependent on the security modules installed on the system. If the cipher strength specified is not supported, an error will be returned when connections are initiated.

NOTE: This configuration setting contains the minimum cipher strength requested from the security library. The actual cipher strength used for the connection is shown by the [SSLStatus](#sslstatus-event-mqtt-component) event.

Use this configuration setting with caution. Requesting a lower cipher strength than necessary could potentially cause serious security vulnerabilities in your application.

When the provider is OpenSSL, [SSLCipherStrength](#SSLCipherStrength) is currently not supported. This functionality is instead made available through the [OpenSSLCipherList](#OpenSSLCipherList) configuration setting.

**SSLClientCACerts**: A newline separated list of CA certificates to use during SSL client certificate validation.This configuration setting is only applicable to server components (e.g., TCPServer) see [SSLServerCACerts](#SSLServerCACerts) for client components (e.g., TCPClient). This setting can be used to optionally specify one or more CA certificates to be used when verifying the client certificate that is presented by the client during the SSL handshake when SSLAuthenticateClients is enabled. When verifying the client's certificate, the certificates trusted by the system will be used as part of the verification process. If the client's CA certificates are not installed to the trusted system store, they may be specified here so they are included when performing the verification process. This configuration setting should be set only if the client's CA certificates are not already trusted on the system and cannot be installed to the trusted system store.

The value of this configuration setting is a newline-separated (CR/LF) list of certificates. For instance:

```text
-----BEGIN CERTIFICATE-----
MIIEKzCCAxOgAwIBAgIRANTET4LIkxdH6P+CFIiHvTowDQYJKoZIhvcNAQELBQAw
... Intermediate Cert ...
eWHV5OW1K53o/atv59sOiW5K3crjFhsBOd5Q+cJJnU+SWinPKtANXMht+EDvYY2w
F0I1XhM+pKj7FjDr+XNj
-----END CERTIFICATE-----
\r \n
-----BEGIN CERTIFICATE-----
MIIEFjCCAv6gAwIBAgIQetu1SMxpnENAnnOz1P+PtTANBgkqhkiG9w0BAQUFADBp
... Root Cert ...
d8q23djXZbVYiIfE9ebr4g3152BlVCHZ2GyPdjhIuLeH21VbT/dyEHHA
-----END CERTIFICATE-----
```

**SSLEnabledCipherSuites**: The cipher suite to be used in an SSL negotiation.This configuration setting enables the cipher suites to be used in SSL negotiation.

By default, the enabled cipher suites will include all available ciphers ("*").

The special value "*" means that the component will pick all of the supported cipher suites. If [SSLEnabledCipherSuites](#SSLEnabledCipherSuites) is set to any other value, only the specified cipher suites will be considered.

Multiple cipher suites are separated by semicolons.

Example values when [SSLProvider](#sslprovider-property-mqtt-component) is set to *Platform* include the following:

```text
obj.config("SSLEnabledCipherSuites=*");
obj.config("SSLEnabledCipherSuites=CALG_AES_256");
obj.config("SSLEnabledCipherSuites=CALG_AES_256;CALG_3DES");
```

 Possible values when [SSLProvider](#sslprovider-property-mqtt-component) is set to *Platform* include the following:

- CALG_3DES
- CALG_3DES_112
- CALG_AES
- CALG_AES_128
- CALG_AES_192
- CALG_AES_256
- CALG_AGREEDKEY_ANY
- CALG_CYLINK_MEK
- CALG_DES
- CALG_DESX
- CALG_DH_EPHEM
- CALG_DH_SF
- CALG_DSS_SIGN
- CALG_ECDH
- CALG_ECDH_EPHEM
- CALG_ECDSA
- CALG_ECMQV
- CALG_HASH_REPLACE_OWF
- CALG_HUGHES_MD5
- CALG_HMAC
- CALG_KEA_KEYX
- CALG_MAC
- CALG_MD2
- CALG_MD4
- CALG_MD5
- CALG_NO_SIGN
- CALG_OID_INFO_CNG_ONLY
- CALG_OID_INFO_PARAMETERS
- CALG_PCT1_MASTER
- CALG_RC2
- CALG_RC4
- CALG_RC5
- CALG_RSA_KEYX
- CALG_RSA_SIGN
- CALG_SCHANNEL_ENC_KEY
- CALG_SCHANNEL_MAC_KEY
- CALG_SCHANNEL_MASTER_HASH
- CALG_SEAL
- CALG_SHA
- CALG_SHA1
- CALG_SHA_256
- CALG_SHA_384
- CALG_SHA_512
- CALG_SKIPJACK
- CALG_SSL2_MASTER
- CALG_SSL3_MASTER
- CALG_SSL3_SHAMD5
- CALG_TEK
- CALG_TLS1_MASTER
- CALG_TLS1PRF

 Example values when [SSLProvider](#sslprovider-property-mqtt-component) is set to *Internal*include the following:

```text
obj.config("SSLEnabledCipherSuites=*");
obj.config("SSLEnabledCipherSuites=TLS_DHE_DSS_WITH_AES_128_CBC_SHA");
obj.config("SSLEnabledCipherSuites=TLS_DHE_DSS_WITH_AES_128_CBC_SHA;TLS_ECDH_RSA_WITH_AES_128_CBC_SHA");
```

 Possible values when [SSLProvider](#sslprovider-property-mqtt-component) is set to *Internal* include the following:

- TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384
- TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
- TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
- TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
- TLS_ECDH_ECDSA_WITH_AES_256_GCM_SHA384
- TLS_RSA_WITH_AES_256_GCM_SHA384
- TLS_RSA_WITH_AES_128_GCM_SHA256
- TLS_ECDH_ECDSA_WITH_AES_128_GCM_SHA256
- TLS_DHE_DSS_WITH_AES_256_GCM_SHA384
- TLS_DHE_RSA_WITH_AES_256_GCM_SHA384
- TLS_ECDH_RSA_WITH_AES_256_GCM_SHA384
- TLS_ECDH_RSA_WITH_AES_128_GCM_SHA256
- TLS_DHE_RSA_WITH_AES_128_GCM_SHA256
- TLS_DHE_DSS_WITH_AES_128_GCM_SHA256
- TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384
- TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256
- TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA384
- TLS_DHE_DSS_WITH_AES_256_CBC_SHA256
- TLS_RSA_WITH_AES_256_CBC_SHA256
- TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384
- TLS_ECDH_RSA_WITH_AES_256_CBC_SHA384
- TLS_DHE_RSA_WITH_AES_256_CBC_SHA256
- TLS_DHE_RSA_WITH_AES_128_CBC_SHA256
- TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256
- TLS_RSA_WITH_AES_128_CBC_SHA256
- TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA256
- TLS_ECDH_RSA_WITH_AES_128_CBC_SHA256
- TLS_DHE_DSS_WITH_AES_128_CBC_SHA256
- TLS_RSA_WITH_AES_256_CBC_SHA
- TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA
- TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA
- TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA
- TLS_DHE_RSA_WITH_AES_256_CBC_SHA
- TLS_ECDH_RSA_WITH_AES_256_CBC_SHA
- TLS_DHE_DSS_WITH_AES_256_CBC_SHA
- TLS_RSA_WITH_AES_128_CBC_SHA
- TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
- TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA
- TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA
- TLS_ECDH_RSA_WITH_AES_128_CBC_SHA
- TLS_DHE_RSA_WITH_AES_128_CBC_SHA
- TLS_DHE_DSS_WITH_AES_128_CBC_SHA
- TLS_ECDHE_ECDSA_WITH_3DES_EDE_CBC_SHA
- TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA
- TLS_ECDH_ECDSA_WITH_3DES_EDE_CBC_SHA
- TLS_ECDH_RSA_WITH_3DES_EDE_CBC_SHA
- TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA
- TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA
- TLS_RSA_WITH_3DES_EDE_CBC_SHA
- TLS_RSA_WITH_DES_CBC_SHA
- TLS_DHE_RSA_WITH_DES_CBC_SHA
- TLS_DHE_DSS_WITH_DES_CBC_SHA
- TLS_RSA_WITH_RC4_128_MD5
- TLS_RSA_WITH_RC4_128_SHA

When TLS 1.3 is negotiated (see [SSLEnabledProtocols](#SSLEnabledProtocols)), only the following cipher suites are supported:

- TLS_AES_256_GCM_SHA384
- TLS_CHACHA20_POLY1305_SHA256
- TLS_AES_128_GCM_SHA256

[SSLEnabledCipherSuites](#SSLEnabledCipherSuites) is used together with [SSLCipherStrength](#SSLCipherStrength).

**SSLEnabledProtocols**: Used to enable/disable the supported security protocols.This configuration setting is used to enable or disable the supported security protocols.

Not all supported protocols are enabled by default. The default value is *4032* for client components, and *3072* for server components. To specify a combination of enabled protocol versions set this config to the binary *OR* of one or more of the following values:

|  |  |
| --- | --- |
| TLS1.3 | 12288 (Hex 3000) |
| TLS1.2 | 3072 (Hex C00) (Default - Client and Server) |
| TLS1.1 | 768 (Hex 300) (Default - Client) |
| TLS1 | 192 (Hex C0) (Default - Client) |
| SSL3 | 48 (Hex 30) |
| SSL2 | 12 (Hex 0C) |

Note that only TLS 1.2 is enabled for server components that accept incoming connections. This adheres to industry standards to ensure a secure connection. Client components enable TLS 1.0, TLS 1.1, and TLS 1.2 by default and will negotiate the highest mutually supported version when connecting to a server, which should be TLS 1.2 in most cases.

**SSLEnabledProtocols: Transport Layer Security (TLS) 1.3 Notes:**

By default when TLS 1.3 is enabled, the component will first try to use the platform TLS 1.3 implementation when the [SSLProvider](#sslprovider-property-mqtt-component) is set to Automatic for all editions. If the platform TLS 1.3 implementation is not available, the internal implementation will be used.

In editions that are designed to run on Windows, [SSLProvider](#sslprovider-property-mqtt-component) can be set to Platform to use the platform implementation instead of the internal implementation. When configured in this manner, please note that the platform provider is supported only on Windows 11/Windows Server 2022 and up. The default internal provider is available on all platforms and is not restricted to any specific OS version.

If set to *1* (Platform provider), please be aware of the following notes:

- The platform provider is available only on Windows 11/Windows Server 2022 and up.
- [SSLEnabledCipherSuites](#SSLEnabledCipherSuites) and other similar SSL configuration settings are not supported.
- If [SSLEnabledProtocols](#SSLEnabledProtocols) includes both TLS 1.3 and TLS 1.2, these restrictions are still applicable even if TLS 1.2 is negotiated. Enabling TLS 1.3 with the platform provider changes the implementation used for all TLS versions.

**SSLEnabledProtocols: SSL2 and SSL3 Notes: **

SSL 2.0 and 3.0 are not supported by the component when the [SSLProvider](#sslprovider-property-mqtt-component) is set to internal. To use SSL 2.0 or SSL 3.0, the platform security API must have the protocols enabled and [SSLProvider](#sslprovider-property-mqtt-component) needs to be set to platform.

**SSLEnableRenegotiation**: Whether the renegotiation_info SSL extension is supported.This configuration setting specifies whether the renegotiation_info SSL extension will be used in the request when using the internal security API. This configuration setting is *false* by default, but it can be set to *true* to enable the extension.

This configuration setting is applicable only when [SSLProvider](#sslprovider-property-mqtt-component) is set to *Internal*.

**SSLIncludeCertChain**: Whether the entire certificate chain is included in the SSLServerAuthentication event.This configuration setting specifies whether the Encoded parameter of the [SSLServerAuthentication](#sslserverauthentication-event-mqtt-component) event contains the full certificate chain. By default this value is False and only the leaf certificate will be present in the Encoded parameter of the [SSLServerAuthentication](#sslserverauthentication-event-mqtt-component) event.

If set to True, all certificates returned by the server will be present in the Encoded parameter of the [SSLServerAuthentication](#sslserverauthentication-event-mqtt-component) event. This includes the leaf certificate, any intermediate certificate, and the root certificate.

**SSLKeyLogFile**: The location of a file where per-session secrets are written for debugging purposes.This configuration setting optionally specifies the full path to a file on disk where per-session secrets are stored for debugging purposes.

When set, the component will save the session secrets in the same format as the SSLKEYLOGFILE environment variable functionality used by most major browsers and tools, such as Chrome, Firefox, and cURL. This file can then be used in tools such as Wireshark to decrypt TLS traffic for debugging purposes. When writing to this file, the component will only append, it will not overwrite previous values.

NOTE: This configuration setting is applicable only when [SSLProvider](#sslprovider-property-mqtt-component) is set to *Internal*.

**SSLNegotiatedCipher**: Returns the negotiated cipher suite.This configuration setting returns the cipher suite negotiated during the SSL handshake.

NOTE: For server components (e.g., TCPServer), this is a per-connection configuration setting accessed by passing the ConnectionId. For example:

```csharp
server.Config("SSLNegotiatedCipher[connId]");
```

**SSLNegotiatedCipherStrength**: Returns the negotiated cipher suite strength.This configuration setting returns the strength of the cipher suite negotiated during the SSL handshake.

NOTE: For server components (e.g., TCPServer), this is a per-connection configuration setting accessed by passing the ConnectionId. For example:

```csharp
server.Config("SSLNegotiatedCipherStrength[connId]");
```

**SSLNegotiatedCipherSuite**: Returns the negotiated cipher suite.This configuration setting returns the cipher suite negotiated during the SSL handshake represented as a single string.

NOTE: For server components (e.g., TCPServer), this is a per-connection configuration setting accessed by passing the ConnectionId. For example:

```csharp
server.Config("SSLNegotiatedCipherSuite[connId]");
```

**SSLNegotiatedKeyExchange**: Returns the negotiated key exchange algorithm.This configuration setting returns the key exchange algorithm negotiated during the SSL handshake.

NOTE: For server components (e.g., TCPServer), this is a per-connection configuration setting accessed by passing the ConnectionId. For example:

```csharp
server.Config("SSLNegotiatedKeyExchange[connId]");
```

**SSLNegotiatedKeyExchangeStrength**: Returns the negotiated key exchange algorithm strength.This configuration setting returns the strength of the key exchange algorithm negotiated during the SSL handshake.

NOTE: For server components (e.g., TCPServer), this is a per-connection configuration setting accessed by passing the ConnectionId. For example:

```csharp
server.Config("SSLNegotiatedKeyExchangeStrength[connId]");
```

**SSLNegotiatedVersion**: Returns the negotiated protocol version.This configuration setting returns the protocol version negotiated during the SSL handshake.

NOTE: For server components (e.g., TCPServer), this is a per-connection configuration setting accessed by passing the ConnectionId. For example:

```csharp
server.Config("SSLNegotiatedVersion[connId]");
```

**SSLSecurityFlags**: Flags that control certificate verification.The following flags are defined (specified in hexadecimal notation). They can be ORed together to exclude multiple conditions:

|  |  |
| --- | --- |
| 0x00000001 | Ignore time validity status of certificate. |
| 0x00000002 | Ignore time validity status of CTL. |
| 0x00000004 | Ignore non-nested certificate times. |
| 0x00000010 | Allow unknown certificate authority. |
| 0x00000020 | Ignore wrong certificate usage. |
| 0x00000100 | Ignore unknown certificate revocation status. |
| 0x00000200 | Ignore unknown CTL signer revocation status. |
| 0x00000400 | Ignore unknown certificate authority revocation status. |
| 0x00000800 | Ignore unknown root revocation status. |
| 0x00008000 | Allow test root certificate. |
| 0x00004000 | Trust test root certificate. |
| 0x80000000 | Ignore non-matching CN (certificate CN non-matching server name). |

This functionality is currently not available when the provider is OpenSSL.

**SSLServerCACerts**: A newline separated list of CA certificates to use during SSL server certificate validation.This configuration setting is only used by client components (e.g., TCPClient) see [SSLClientCACerts](#SSLClientCACerts) for server components (e.g., TCPServer). This configuration setting can be used to optionally specify one or more CA certificates to be used when connecting to the server and verifying the server certificate. When verifying the server's certificate, the certificates trusted by the system will be used as part of the verification process. If the server's CA certificates are not installed to the trusted system store, they may be specified here so they are included when performing the verification process. This configuration setting should be set only if the server's CA certificates are not already trusted on the system and cannot be installed to the trusted system store.

The value of this configuration setting is a newline-separated (CR/LF) list of certificates. For instance:

```text
-----BEGIN CERTIFICATE-----
MIIEKzCCAxOgAwIBAgIRANTET4LIkxdH6P+CFIiHvTowDQYJKoZIhvcNAQELBQAw
... Intermediate Cert...
eWHV5OW1K53o/atv59sOiW5K3crjFhsBOd5Q+cJJnU+SWinPKtANXMht+EDvYY2w
F0I1XhM+pKj7FjDr+XNj
-----END CERTIFICATE-----
\r \n
-----BEGIN CERTIFICATE-----
MIIEFjCCAv6gAwIBAgIQetu1SMxpnENAnnOz1P+PtTANBgkqhkiG9w0BAQUFADBp
... Root Cert...
d8q23djXZbVYiIfE9ebr4g3152BlVCHZ2GyPdjhIuLeH21VbT/dyEHHA
-----END CERTIFICATE-----
```

**TLS12SignatureAlgorithms**: Defines the allowed TLS 1.2 signature algorithms when SSLProvider is set to Internal.This configuration setting specifies the allowed server certificate signature algorithms when [SSLProvider](#sslprovider-property-mqtt-component) is set to *Internal* and [SSLEnabledProtocols](#SSLEnabledProtocols) is set to allow TLS 1.2.

When specified the component will verify that the server certificate signature algorithm is among the values specified in this configuration setting. If the server certificate signature algorithm is unsupported, the component raises an exception.

The format of this value is a comma-separated list of hash-signature combinations. For instance:

```csharp
component.SSLProvider = TCPClientSSLProviders.sslpInternal;
component.Config("SSLEnabledProtocols=3072"); //TLS 1.2
component.Config("TLS12SignatureAlgorithms=sha256-rsa,sha256-dsa,sha1-rsa,sha1-dsa");
```

 The default value for this configuration setting is *sha512-ecdsa,sha512-rsa,sha512-dsa,sha384-ecdsa,sha384-rsa,sha384-dsa,sha256-ecdsa,sha256-rsa,sha256-dsa,sha224-ecdsa,sha224-rsa,sha224-dsa,sha1-ecdsa,sha1-rsa,sha1-dsa*.

To not restrict the server's certificate signature algorithm, specify an empty string as the value for this configuration setting, which will cause the signature_algorithms TLS 1.2 extension to not be sent.

**TLS12SupportedGroups**: The supported groups for ECC.This configuration setting specifies a comma-separated list of named groups used in TLS 1.2 for ECC.

The default value is *ecdhe_secp256r1,ecdhe_secp384r1,ecdhe_secp521r1*.

When using TLS 1.2 and [SSLProvider](#sslprovider-property-mqtt-component) is set to *Internal*, the values refer to the supported groups for ECC. The following values are supported:

- "ecdhe_secp256r1" (default)
- "ecdhe_secp384r1" (default)
- "ecdhe_secp521r1" (default)

**TLS13KeyShareGroups**: The groups for which to pregenerate key shares.This configuration setting specifies a comma-separated list of named groups used in TLS 1.3 for key exchange. The groups specified here will have key share data pregenerated locally before establishing a connection. This can prevent an additional roundtrip during the handshake if the group is supported by the server.

The default value is set to balance common supported groups and the computational resources required to generate key shares. As a result, only some groups are included by default in this configuration setting.

NOTE: All supported groups can always be used during the handshake even if not listed here, but if a group is used that is not present in this list, it will incur an additional roundtrip and time to generate the key share for that group.

In most cases, this configuration setting does not need to be modified. This should be modified only if there is a specific reason to do so.

The default value is *ecdhe_x25519,ecdhe_secp256r1,ecdhe_secp384r1,ffdhe_2048,ffdhe_3072*

The values are ordered from most preferred to least preferred. The following values are supported:

- "ecdhe_x25519" (default)
- "ecdhe_x448"
- "ecdhe_secp256r1" (default)
- "ecdhe_secp384r1" (default)
- "ecdhe_secp521r1"
- "ffdhe_2048" (default)
- "ffdhe_3072" (default)
- "ffdhe_4096"
- "ffdhe_6144"
- "ffdhe_8192"

**TLS13SignatureAlgorithms**: The allowed certificate signature algorithms.This configuration setting holds a comma-separated list of allowed signature algorithms. Possible values include the following:

- "ed25519" (default)
- "ed448" (default)
- "ecdsa_secp256r1_sha256" (default)
- "ecdsa_secp384r1_sha384" (default)
- "ecdsa_secp521r1_sha512" (default)
- "rsa_pkcs1_sha256" (default)
- "rsa_pkcs1_sha384" (default)
- "rsa_pkcs1_sha512" (default)
- "rsa_pss_sha256" (default)
- "rsa_pss_sha384" (default)
- "rsa_pss_sha512" (default)

 The default value is *rsa_pss_sha256,rsa_pss_sha384,rsa_pss_sha512,rsa_pkcs1_sha256,rsa_pkcs1_sha384,rsa_pkcs1_sha512,ecdsa_secp256r1_sha256,ecdsa_secp384r1_sha384,ecdsa_secp521r1_sha512,ed25519,ed448*. This configuration setting is applicable only when [SSLEnabledProtocols](#SSLEnabledProtocols) includes TLS 1.3.

**TLS13SupportedGroups**: The supported groups for (EC)DHE key exchange.This configuration setting specifies a comma-separated list of named groups used in TLS 1.3 for key exchange. This configuration setting should be modified only if there is a specific reason to do so.

The default value is *ecdhe_x25519,ecdhe_x448,ecdhe_secp256r1,ecdhe_secp384r1,ecdhe_secp521r1,ffdhe_2048,ffdhe_3072,ffdhe_4096,ffdhe_6144,ffdhe_8192,mlkem_512,mlkem_768,mlkem_1024,x25519_mlkem_768,secp256r1_mlkem_768*

The values are ordered from most preferred to least preferred. The following values are supported:

- "ecdhe_x25519" (default)
- "ecdhe_x448" (default)
- "ecdhe_secp256r1" (default)
- "ecdhe_secp384r1" (default)
- "ecdhe_secp521r1" (default)
- "ffdhe_2048" (default)
- "ffdhe_3072" (default)
- "ffdhe_4096" (default)
- "ffdhe_6144" (default)
- "ffdhe_8192" (default)
- "mlkem_512" (default)
- "mlkem_768" (default)
- "mlkem_1024" (default)
- "x25519_mlkem_768" (default)
- "secp256r1_mlkem_768" (default)

Post-quantum algorithms (*mlkem_512,mlkem_768,mlkem_1024,x25519_mlkem_768,secp256r1_mlkem_768*) in our components rely on the operating system's underlying cryptographic primitives. The following platforms are currently supported:

-  Windows Server 2025
-  Windows 11 24H2
-  Windows 11 25H2

### Socket Config Settings

**AbsoluteTimeout**: Determines whether timeouts are inactivity timeouts or absolute timeouts.If [AbsoluteTimeout](#AbsoluteTimeout) is set to True, any method that does not complete within [Timeout](#timeout-property-mqtt-component) seconds will be aborted. By default, *AbsoluteTimeout* is False, and the timeout is an inactivity timeout.

NOTE: This option is not valid for User Datagram Protocol (UDP) ports.

**FirewallData**: Used to send extra data to the firewall.When the firewall is a tunneling proxy, use this property to send custom (additional) headers to the firewall (e.g., headers for custom authentication schemes).

**InBufferSize**: The size in bytes of the incoming queue of the socket.This is the size of an internal queue in the Transmission Control Protocol (TCP)/IP stack. You can increase or decrease its size depending on the amount of data that you will be receiving. In some cases, increasing the value of the *InBufferSize* setting can provide significant improvements in performance.

Some TCP/IP implementations do not support variable buffer sizes. If that is the case, when the component is activated the *InBufferSize* reverts to its defined size. The same happens if you attempt to make it too large or too small.

**OutBufferSize**: The size in bytes of the outgoing queue of the socket.This is the size of an internal queue in the TCP/IP stack. You can increase or decrease its size depending on the amount of data that you will be sending. In some cases, increasing the value of the *OutBufferSize* setting can provide significant improvements in performance.

Some TCP/IP implementations do not support variable buffer sizes. If that is the case, when the component is activated the *OutBufferSize* reverts to its defined size. The same happens if you attempt to make it too large or too small.

### Base Config Settings

**BuildInfo**: Information about the product's build.When queried, this setting will return a string containing information about the product's build.

**CodePage**: The system code page used for Unicode to Multibyte translations.The default code page is Unicode UTF-8 (65001).

The following is a list of valid code page identifiers:

|  |  |
| --- | --- |
| Identifier | Name |
| 037 | IBM EBCDIC - U.S./Canada |
| 437 | OEM - United States |
| 500 | IBM EBCDIC - International |
| 708 | Arabic - ASMO 708 |
| 709 | Arabic - ASMO 449+, BCON V4 |
| 710 | Arabic - Transparent Arabic |
| 720 | Arabic - Transparent ASMO |
| 737 | OEM - Greek (formerly 437G) |
| 775 | OEM - Baltic |
| 850 | OEM - Multilingual Latin I |
| 852 | OEM - Latin II |
| 855 | OEM - Cyrillic (primarily Russian) |
| 857 | OEM - Turkish |
| 858 | OEM - Multilingual Latin I + Euro symbol |
| 860 | OEM - Portuguese |
| 861 | OEM - Icelandic |
| 862 | OEM - Hebrew |
| 863 | OEM - Canadian-French |
| 864 | OEM - Arabic |
| 865 | OEM - Nordic |
| 866 | OEM - Russian |
| 869 | OEM - Modern Greek |
| 870 | IBM EBCDIC - Multilingual/ROECE (Latin-2) |
| 874 | ANSI/OEM - Thai (same as 28605, ISO 8859-15) |
| 875 | IBM EBCDIC - Modern Greek |
| 932 | ANSI/OEM - Japanese, Shift-JIS |
| 936 | ANSI/OEM - Simplified Chinese (PRC, Singapore) |
| 949 | ANSI/OEM - Korean (Unified Hangul Code) |
| 950 | ANSI/OEM - Traditional Chinese (Taiwan; Hong Kong SAR, PRC) |
| 1026 | IBM EBCDIC - Turkish (Latin-5) |
| 1047 | IBM EBCDIC - Latin 1/Open System |
| 1140 | IBM EBCDIC - U.S./Canada (037 + Euro symbol) |
| 1141 | IBM EBCDIC - Germany (20273 + Euro symbol) |
| 1142 | IBM EBCDIC - Denmark/Norway (20277 + Euro symbol) |
| 1143 | IBM EBCDIC - Finland/Sweden (20278 + Euro symbol) |
| 1144 | IBM EBCDIC - Italy (20280 + Euro symbol) |
| 1145 | IBM EBCDIC - Latin America/Spain (20284 + Euro symbol) |
| 1146 | IBM EBCDIC - United Kingdom (20285 + Euro symbol) |
| 1147 | IBM EBCDIC - France (20297 + Euro symbol) |
| 1148 | IBM EBCDIC - International (500 + Euro symbol) |
| 1149 | IBM EBCDIC - Icelandic (20871 + Euro symbol) |
| 1200 | Unicode UCS-2 Little-Endian (BMP of ISO 10646) |
| 1201 | Unicode UCS-2 Big-Endian |
| 1250 | ANSI - Central European |
| 1251 | ANSI - Cyrillic |
| 1252 | ANSI - Latin I |
| 1253 | ANSI - Greek |
| 1254 | ANSI - Turkish |
| 1255 | ANSI - Hebrew |
| 1256 | ANSI - Arabic |
| 1257 | ANSI - Baltic |
| 1258 | ANSI/OEM - Vietnamese |
| 1361 | Korean (Johab) |
| 10000 | MAC - Roman |
| 10001 | MAC - Japanese |
| 10002 | MAC - Traditional Chinese (Big5) |
| 10003 | MAC - Korean |
| 10004 | MAC - Arabic |
| 10005 | MAC - Hebrew |
| 10006 | MAC - Greek I |
| 10007 | MAC - Cyrillic |
| 10008 | MAC - Simplified Chinese (GB 2312) |
| 10010 | MAC - Romania |
| 10017 | MAC - Ukraine |
| 10021 | MAC - Thai |
| 10029 | MAC - Latin II |
| 10079 | MAC - Icelandic |
| 10081 | MAC - Turkish |
| 10082 | MAC - Croatia |
| 12000 | Unicode UCS-4 Little-Endian |
| 12001 | Unicode UCS-4 Big-Endian |
| 20000 | CNS - Taiwan |
| 20001 | TCA - Taiwan |
| 20002 | Eten - Taiwan |
| 20003 | IBM5550 - Taiwan |
| 20004 | TeleText - Taiwan |
| 20005 | Wang - Taiwan |
| 20105 | IA5 IRV International Alphabet No. 5 (7-bit) |
| 20106 | IA5 German (7-bit) |
| 20107 | IA5 Swedish (7-bit) |
| 20108 | IA5 Norwegian (7-bit) |
| 20127 | US-ASCII (7-bit) |
| 20261 | T.61 |
| 20269 | ISO 6937 Non-Spacing Accent |
| 20273 | IBM EBCDIC - Germany |
| 20277 | IBM EBCDIC - Denmark/Norway |
| 20278 | IBM EBCDIC - Finland/Sweden |
| 20280 | IBM EBCDIC - Italy |
| 20284 | IBM EBCDIC - Latin America/Spain |
| 20285 | IBM EBCDIC - United Kingdom |
| 20290 | IBM EBCDIC - Japanese Katakana Extended |
| 20297 | IBM EBCDIC - France |
| 20420 | IBM EBCDIC - Arabic |
| 20423 | IBM EBCDIC - Greek |
| 20424 | IBM EBCDIC - Hebrew |
| 20833 | IBM EBCDIC - Korean Extended |
| 20838 | IBM EBCDIC - Thai |
| 20866 | Russian - KOI8-R |
| 20871 | IBM EBCDIC - Icelandic |
| 20880 | IBM EBCDIC - Cyrillic (Russian) |
| 20905 | IBM EBCDIC - Turkish |
| 20924 | IBM EBCDIC - Latin-1/Open System (1047 + Euro symbol) |
| 20932 | JIS X 0208-1990 & 0121-1990 |
| 20936 | Simplified Chinese (GB2312) |
| 21025 | IBM EBCDIC - Cyrillic (Serbian, Bulgarian) |
| 21027 | Extended Alpha Lowercase |
| 21866 | Ukrainian (KOI8-U) |
| 28591 | ISO 8859-1 Latin I |
| 28592 | ISO 8859-2 Central Europe |
| 28593 | ISO 8859-3 Latin 3 |
| 28594 | ISO 8859-4 Baltic |
| 28595 | ISO 8859-5 Cyrillic |
| 28596 | ISO 8859-6 Arabic |
| 28597 | ISO 8859-7 Greek |
| 28598 | ISO 8859-8 Hebrew |
| 28599 | ISO 8859-9 Latin 5 |
| 28605 | ISO 8859-15 Latin 9 |
| 29001 | Europa 3 |
| 38598 | ISO 8859-8 Hebrew |
| 50220 | ISO 2022 Japanese with no halfwidth Katakana |
| 50221 | ISO 2022 Japanese with halfwidth Katakana |
| 50222 | ISO 2022 Japanese JIS X 0201-1989 |
| 50225 | ISO 2022 Korean |
| 50227 | ISO 2022 Simplified Chinese |
| 50229 | ISO 2022 Traditional Chinese |
| 50930 | Japanese (Katakana) Extended |
| 50931 | US/Canada and Japanese |
| 50933 | Korean Extended and Korean |
| 50935 | Simplified Chinese Extended and Simplified Chinese |
| 50936 | Simplified Chinese |
| 50937 | US/Canada and Traditional Chinese |
| 50939 | Japanese (Latin) Extended and Japanese |
| 51932 | EUC - Japanese |
| 51936 | EUC - Simplified Chinese |
| 51949 | EUC - Korean |
| 51950 | EUC - Traditional Chinese |
| 52936 | HZ-GB2312 Simplified Chinese |
| 54936 | Windows XP: GB18030 Simplified Chinese (4 Byte) |
| 57002 | ISCII Devanagari |
| 57003 | ISCII Bengali |
| 57004 | ISCII Tamil |
| 57005 | ISCII Telugu |
| 57006 | ISCII Assamese |
| 57007 | ISCII Oriya |
| 57008 | ISCII Kannada |
| 57009 | ISCII Malayalam |
| 57010 | ISCII Gujarati |
| 57011 | ISCII Punjabi |
| 65000 | Unicode UTF-7 |
| 65001 | Unicode UTF-8 |

 The following is a list of valid code page identifiers for Mac OS only:

|  |  |
| --- | --- |
| Identifier | Name |
| 1 | ASCII |
| 2 | NEXTSTEP |
| 3 | JapaneseEUC |
| 4 | UTF8 |
| 5 | ISOLatin1 |
| 6 | Symbol |
| 7 | NonLossyASCII |
| 8 | ShiftJIS |
| 9 | ISOLatin2 |
| 10 | Unicode |
| 11 | WindowsCP1251 |
| 12 | WindowsCP1252 |
| 13 | WindowsCP1253 |
| 14 | WindowsCP1254 |
| 15 | WindowsCP1250 |
| 21 | ISO2022JP |
| 30 | MacOSRoman |
| 10 | UTF16String |
| 0x90000100 | UTF16BigEndian |
| 0x94000100 | UTF16LittleEndian |
| 0x8c000100 | UTF32String |
| 0x98000100 | UTF32BigEndian |
| 0x9c000100 | UTF32LittleEndian |
| 65536 | Proprietary |

**LicenseInfo**: Information about the current license.When queried, this setting will return a string containing information about the license this instance of a component is using. It will return the following information:

- Product: The product the license is for.
- Product Key: The key the license was generated from.
- License Source: Where the license was found (e.g., RuntimeLicense, License File).
- License Type: The type of license installed (e.g., Royalty Free, Single Server).
- Last Valid Build: The last valid build number for which the license will work.

**MaskSensitiveData**: Whether sensitive data is masked in log messages.In certain circumstances it may be beneficial to mask sensitive data, like passwords, in log messages. Set this to *true* to mask sensitive data. The default is *true*.

**UseFIPSCompliantAPI**: Tells the component whether or not to use FIPS certified APIs.When set to *true*, the component will utilize the underlying operating system's certified APIs. Java editions, regardless of OS, utilize Bouncy Castle Federal Information Processing Standards (FIPS), while all other Windows editions make use of Microsoft security libraries.

FIPS mode can be enabled by setting the *UseFIPSCompliantAPI* configuration setting to *true*. This is a static setting that applies to all instances of all components of the toolkit within the process. It is recommended to enable or disable this setting once before the component has been used to establish a connection. Enabling FIPS while an instance of the component is active and connected may result in unexpected behavior.

For more details, please see the [FIPS 140-2 Compliance](https://www.nsoftware.com/kb/articles/fips.rst) article.

NOTE: This setting is applicable only on Windows.

NOTE: Enabling FIPS compliance requires a special license; please contact [sales@nsoftware.com](mailto:sales@nsoftware.com) for details.

**UseInternalSecurityAPI**: Whether or not to use the system security libraries or an internal implementation. When set to *false*, the component will use the system security libraries by default to perform cryptographic functions where applicable.

Setting this configuration setting to *true* tells the component to use the internal implementation instead of using the system security libraries.

 This setting is set to *false* by default on all platforms.

# Trappable Errors ([MQTT](#mqtt-component) Component)

### MQTT Errors

|  |  |
| --- | --- |
| 500 | MQTT protocol error. Refer to the error message for more information. |
| 501 | Packet Id pool exhausted, no more packet Ids are available. |
| 502 | Invalid topic name. Refer to the error message for more information. |
| 503 | Invalid topic filter. Refer to the error message for more information. |
| 504 | Message data is malformed. |
| 505 | Invalid QoS value. Refer to the error message for more information. |

### WebSocket Errors

|  |  |
| --- | --- |
| 4001 | Error transmitting packet. |
| 4002 | Error sending CLOSE packet. |
| 4003 | General protocol error. |

### HTTP Errors

|  |  |
| --- | --- |
| 118 | Firewall error. The error description contains the detailed message. |
| 143 | Busy executing current method. |
| 151 | HTTP protocol error. The error message has the server response. |
| 152 | No server specified in URL. |
| 153 | Specified URLScheme is invalid. |
| 155 | Range operation is not supported by server. |
| 156 | Invalid cookie index (out of range). |
| 301 | Interrupted. |
| 302 | Cannot open AttachedFile. |

The component may also return one of the following error codes, which are inherited from other components.

### TCPClient Errors

|  |  |
| --- | --- |
| 100 | You cannot change the [RemotePort](#remoteport-property-mqtt-component) at this time. A connection is in progress. |
| 101 | You cannot change the [RemoteHost](#remotehost-property-mqtt-component) (Server) at this time. A connection is in progress. |
| 102 | The [RemoteHost](#remotehost-property-mqtt-component) address is invalid (0.0.0.0). |
| 104 | Already connected. If you want to reconnect, close the current connection first. |
| 106 | You cannot change the [LocalPort](#localport-property-mqtt-component) at this time. A connection is in progress. |
| 107 | You cannot change the [LocalHost](#localhost-property-mqtt-component) at this time. A connection is in progress. |
| 112 | You cannot change [MaxLineLength](#MaxLineLength) at this time. A connection is in progress. |
| 116 | [RemotePort](#remoteport-property-mqtt-component) cannot be zero. Please specify a valid service port number. |
| 117 | You cannot change the UseConnection option while the component is active. |
| 135 | Operation would block. |
| 201 | Timeout. |
| 211 | Action impossible in control's present state. |
| 212 | Action impossible while not connected. |
| 213 | Action impossible while listening. |
| 301 | Timeout. |
| 302 | Could not open file. |
| 434 | Unable to convert string to selected CodePage. |
| 1105 | Already connecting. If you want to reconnect, close the current connection first. |
| 1117 | You need to connect first. |
| 1119 | You cannot change the LocalHost at this time. A connection is in progress. |
| 1120 | Connection dropped by remote host. |

### SSL Errors

|  |  |
| --- | --- |
| 270 | Cannot load specified security library. |
| 271 | Cannot open certificate store. |
| 272 | Cannot find specified certificate. |
| 273 | Cannot acquire security credentials. |
| 274 | Cannot find certificate chain. |
| 275 | Cannot verify certificate chain. |
| 276 | Error during handshake. |
| 280 | Error verifying certificate. |
| 281 | Could not find client certificate. |
| 282 | Could not find server certificate. |
| 283 | Error encrypting data. |
| 284 | Error decrypting data. |

### TCP/IP Errors

|  |  |
| --- | --- |
| 10004 | [10004] Interrupted system call. |
| 10009 | [10009] Bad file number. |
| 10013 | [10013] Access denied. |
| 10014 | [10014] Bad address. |
| 10022 | [10022] Invalid argument. |
| 10024 | [10024] Too many open files. |
| 10035 | [10035] Operation would block. |
| 10036 | [10036] Operation now in progress. |
| 10037 | [10037] Operation already in progress. |
| 10038 | [10038] Socket operation on nonsocket. |
| 10039 | [10039] Destination address required. |
| 10040 | [10040] Message is too long. |
| 10041 | [10041] Protocol wrong type for socket. |
| 10042 | [10042] Bad protocol option. |
| 10043 | [10043] Protocol is not supported. |
| 10044 | [10044] Socket type is not supported. |
| 10045 | [10045] Operation is not supported on socket. |
| 10046 | [10046] Protocol family is not supported. |
| 10047 | [10047] Address family is not supported by protocol family. |
| 10048 | [10048] Address already in use. |
| 10049 | [10049] Cannot assign requested address. |
| 10050 | [10050] Network is down. |
| 10051 | [10051] Network is unreachable. |
| 10052 | [10052] Net dropped connection or reset. |
| 10053 | [10053] Software caused connection abort. |
| 10054 | [10054] Connection reset by peer. |
| 10055 | [10055] No buffer space available. |
| 10056 | [10056] Socket is already connected. |
| 10057 | [10057] Socket is not connected. |
| 10058 | [10058] Cannot send after socket shutdown. |
| 10059 | [10059] Too many references, cannot splice. |
| 10060 | [10060] Connection timed out. |
| 10061 | [10061] Connection refused. |
| 10062 | [10062] Too many levels of symbolic links. |
| 10063 | [10063] File name is too long. |
| 10064 | [10064] Host is down. |
| 10065 | [10065] No route to host. |
| 10066 | [10066] Directory is not empty |
| 10067 | [10067] Too many processes. |
| 10068 | [10068] Too many users. |
| 10069 | [10069] Disc Quota Exceeded. |
| 10070 | [10070] Stale NFS file handle. |
| 10071 | [10071] Too many levels of remote in path. |
| 10091 | [10091] Network subsystem is unavailable. |
| 10092 | [10092] WINSOCK DLL Version out of range. |
| 10093 | [10093] Winsock is not loaded yet. |
| 11001 | [11001] Host not found. |
| 11002 | [11002] Nonauthoritative 'Host not found' (try again or check DNS setup). |
| 11003 | [11003] Nonrecoverable errors: FORMERR, REFUSED, NOTIMP. |
| 11004 | [11004] Valid name, no data record (check DNS setup). |