IPWorks MQ 2022 .NET Edition
Version 22.0 [Build 8369]

MQTT Component

Properties   Methods   Events   Config Settings   Errors  

A lightweight, fully-featured MQTT client implementation.

Syntax

nsoftware.IPWorksMQ.Mqtt

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 property and call the ConnectTo method, passing it the server's hostname and port number.

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

If CleanSession is True, check the SessionPresent configuration setting once connected to determine whether the server actually had any session state saved.

Refer to CleanSession, SaveSession, and RestoreSession for more information about MQTT sessions and session state persistence; refer to WillTopic, WillMessage, WillQOS, and WillRetain for more information about MQTT Wills.

Basic Connection Example 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 and Unsubscribe 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 // 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, and potentially also the MessageAck, 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 // 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 and Unsubscribe for more information about subscriptions and topic filters.

Publishing Messages

To publish messages to topics, use the PublishMessage and PublishData methods.

PublishMessage is used to publish a message with a string payload, while PublishData 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 // 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 and PublishMessage 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:

Property List


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

CleanSessionDetermines whether a clean session is used once connected.
ClientIdA string that uniquely identifies this instance of the component to the server.
ConnectedTriggers a connection or disconnection.
FirewallA set of properties related to firewall access.
IncomingMessagesCollection of incoming messages with QoS > 0 that have not been fully acknowledged.
KeepAliveIntervalThe maximum period of inactivity the component will allow before sending a keep-alive packet.
LocalHostThe name of the local host or user-assigned IP interface through which connections are initiated or accepted.
LocalPortThe TCP port in the local host where the component binds.
OutgoingMessagesCollection of outgoing messages with QoS > 0 that have not been fully acknowledged.
PasswordA password if authentication is to be used.
ReadyToSendIndicates whether the component is ready to send data.
RemoteHostThe address of the remote host. Domain names are resolved to IP addresses.
RemotePortThe port of the MQTT server (default is 1883). The default port for SSL is 8883.
SSLAcceptServerCertInstructs the component to unconditionally accept the server certificate that matches the supplied certificate.
SSLCertThe certificate to be used during SSL negotiation.
SSLEnabledWhether TLS/SSL is enabled.
SSLProviderThis specifies the SSL/TLS implementation to use.
SSLServerCertThe server certificate for the last established connection.
TimeoutA timeout for the component.
UserA username if authentication is to be used.
VersionThe MQTT protocol version that the component will conform to.
WillMessageThe message that the server should publish in the event of an ungraceful disconnection.
WillTopicThe 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.

ConfigSets or retrieves a configuration setting.
ConnectConnects to the remote host.
ConnectToConnects to the remote host.
DisconnectThis method disconnects from the remote host.
DoEventsProcesses events from the internal message queue.
InterruptInterrupt the current action and disconnects from the remote host.
PublishDataPublishes a message with a raw data payload.
PublishMessagePublishes a message with a string payload.
ResetReset the component.
RestoreSessionRestores session state data.
SaveSessionSaves session state data.
SubscribeSubscribes the component to one or more topic filters.
UnsubscribeUnsubscribes 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.

ConnectedThis event is fired immediately after a connection completes (or fails).
ConnectionStatusThis event is fired to indicate changes in the connection state.
DisconnectedThis event is fired when a connection is closed.
ErrorInformation about errors during data delivery.
LogFires once for each log message.
MessageAckFired when an incoming or outgoing message has completed all acknowledgment steps.
MessageInFired when an incoming message has been received and/or fully acknowledged.
MessageOutFired when an outgoing message has been sent and/or fully acknowledged.
ReadyToSendFired when the component is ready to send data.
SSLServerAuthenticationFired after the server presents its certificate to the client.
SSLStatusShows the progress of the secure connection.
SubscribedFires for each topic filter subscription the server acknowledges.
UnsubscribedFires 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.

AutoReconnectWhether to automatically attempt to reconnect in the event of a connection error.
ClientTopicAliasMaxThe maximum value the client will accept for a topic alias sent by the server.
ConnAckPropertiesJSON string containing the properties returned in the CONNACK packet.
ConnectionTimeoutHow long to wait for a connection attempt to succeed.
ConnectPropertiesJSON string specifying properties to be included in the CONNECT packet.
DisconnectPropertiesJSON string containing DISCONNECT packet properties.
DisconnectReasonCodeCode describing the reason the client or server closed the connection.
DuplicateWhether to set the Duplicate flag when publishing a message.
IncomingUserPropCountThe size of the IncomingUserPropName and IncomingUserPropValue arrays.
IncomingUserPropName[i]The name of the user property at index i.
IncomingUserPropValue[i]The value of the user property at index i.
LogLevelThe level of detail that is logged.
OutgoingMessagePropertiesJSON string specifying properties to be included in the PUBLISH packet.
OutgoingPacketIdThe packet Id of the last message published.
OutgoingUserPropCountControls the size of the OutgoingUserPropName and OutgoingUserPropValue configuration arrays.
OutgoingUserPropName[i]The name of the User Property at index i.
OutgoingUserPropValue[i]The value of the User Property at index i.
RepublishIntervalHow many seconds to wait before republishing unacknowledged messages.
ResponseTopicTopic name for a response message.
RetainWhether to set the Retain flag when publishing a message.
SendCustomPacketSends a packet constructed using the supplied hex byte string.
ServerTopicAliasMaxThe highest value that the Server will accept as a Topic Alias sent by the Client.
SessionExpIntervalThe length of time in seconds the client and server should store session state data after the connection is closed.
SessionPresentWhen connecting with CleanSession disabled, indicates whether the server actually had any previous session data stored.
SessionStateFileFile to use for saving and restoring session data.
SubscriptionIdentifierA numeric subscription identifier included in SUBSCRIBE packet which will be returned with messages delivered for that subscription.
TopicAliasValue that is used to identify the Topic instead of using the Topic Name in order to reduce packet size.
TopicDelimiterThe string to use as a delimiter in a topic filter list string.
TopicNLArrayList of No Local option flags for subscription topic filters.
TopicQOSArrayComma-separated list of topic filter QoS values to use when subscribing.
TopicRAPArrayList of Retain As Published option flags for subscription topic filters.
TopicRHArrayList of Retain Handling option values for subscription topic filters.
WillPropertiesJSON string specifying will properties to be included in the CONNECT packet.
WillQOSThe QoS value to use for the Will message.
WillRetainWhether the server should retain the Will message after publishing it.
CloseStreamAfterTransferIf true, the component will close the upload or download stream after the transfer.
ConnectionTimeoutSets a separate timeout value for establishing a connection.
FirewallAutoDetectTells the component whether or not to automatically detect and use firewall system settings, if available.
FirewallHostName or IP address of firewall (optional).
FirewallListenerIf true, the component binds to a SOCKS firewall as a server (TCPClient only).
FirewallPasswordPassword to be used if authentication is to be used when connecting through the firewall.
FirewallPortThe TCP port for the FirewallHost;.
FirewallTypeDetermines the type of firewall to connect through.
FirewallUserA user name if authentication is to be used connecting through a firewall.
KeepAliveIntervalThe retry interval, in milliseconds, to be used when a TCP keep-alive packet is sent and no response is received.
KeepAliveTimeThe inactivity time in milliseconds before a TCP keep-alive packet is sent.
LingerWhen set to True, connections are terminated gracefully.
LingerTimeTime in seconds to have the connection linger.
LocalHostThe name of the local host through which connections are initiated or accepted.
LocalPortThe port in the local host where the component binds.
MaxLineLengthThe maximum amount of data to accumulate when no EOL is found.
MaxTransferRateThe transfer rate limit in bytes per second.
ProxyExceptionsListA semicolon separated list of hosts and IPs to bypass when using a proxy.
TCPKeepAliveDetermines whether or not the keep alive socket option is enabled.
TcpNoDelayWhether or not to delay when sending packets.
UseIPv6Whether to use IPv6.
UseNTLMv2Whether to use NTLM V2.
CACertFilePathsThe paths to CA certificate files when using Mono on Unix/Linux.
LogSSLPacketsControls whether SSL packets are logged when using the internal security API.
ReuseSSLSessionDetermines if the SSL session is reused.
SSLCACertsA newline separated list of CA certificate to use during SSL client authentication.
SSLCheckCRLWhether to check the Certificate Revocation List for the server certificate.
SSLCipherStrengthThe minimum cipher strength used for bulk encryption.
SSLEnabledCipherSuitesThe cipher suite to be used in an SSL negotiation.
SSLEnabledProtocolsUsed to enable/disable the supported security protocols.
SSLEnableRenegotiationWhether the renegotiation_info SSL extension is supported.
SSLIncludeCertChainWhether the entire certificate chain is included in the SSLServerAuthentication event.
SSLKeyLogFileThe location of a file where per-session secrets are written for debugging purposes.
SSLNegotiatedCipherReturns the negotiated ciphersuite.
SSLNegotiatedCipherStrengthReturns the negotiated ciphersuite strength.
SSLNegotiatedCipherSuiteReturns the negotiated ciphersuite.
SSLNegotiatedKeyExchangeReturns the negotiated key exchange algorithm.
SSLNegotiatedKeyExchangeStrengthReturns the negotiated key exchange algorithm strength.
SSLNegotiatedVersionReturns the negotiated protocol version.
SSLSecurityFlagsFlags that control certificate verification.
SSLServerCACertsA newline separated list of CA certificate to use during SSL server certificate validation.
TLS12SignatureAlgorithmsDefines the allowed TLS 1.2 signature algorithms when SSLProvider is set to Internal.
TLS12SupportedGroupsThe supported groups for ECC.
TLS13KeyShareGroupsThe groups for which to pregenerate key shares.
TLS13SignatureAlgorithmsThe allowed certificate signature algorithms.
TLS13SupportedGroupsThe supported groups for (EC)DHE key exchange.
AbsoluteTimeoutDetermines whether timeouts are inactivity timeouts or absolute timeouts.
FirewallDataUsed to send extra data to the firewall.
InBufferSizeThe size in bytes of the incoming queue of the socket.
OutBufferSizeThe size in bytes of the outgoing queue of the socket.

CleanSession Property (MQTT Component)

Determines whether a clean session is used once connected.

Syntax

public bool CleanSession { get; set; }
Public Property CleanSession As Boolean

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.)

By default, CleanSession is true, so the server will discard any state data previously associated with the current ClientId 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. 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),
  • 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 (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 method be used to load any previously saved (client-side) session data from a previous session before calling Connect. (Successful calls to RestoreSession will automatically set CleanSession to False.)

Similarly, once disconnected, save the string returned by SaveSession 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 and RestoreSession 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 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 and start a new clean session.

For more information on session expiration in MQTT 5, see the SessionExpInterval config. Setting CleanSession to True in v3.1.1 is equivalent to setting CleanSession to True AND setting 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.

This property is not available at design time.

ClientId Property (MQTT Component)

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

Syntax

public string ClientId { get; set; }
Public Property ClientId As String

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 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 is called, the component's behavior depends on value of CleanSession. If CleanSession is True, the component will automatically generate a unique value for ClientId before connecting. If CleanSession is False, the component throws an exception.

This property is not available at design time.

Connected Property (MQTT Component)

Triggers a connection or disconnection.

Syntax

public bool Connected { get; set; }
Public Property Connected As Boolean

Default Value

False

Remarks

This property triggers a connection or disconnection. Setting this property to True makes the component attempt to connect to the host identified by the RemoteHost property. If successful, after the connection is achieved the value of the property changes to True and the Connected event is fired.

Setting this property to False closes the connection.

By default the component will connect in plaintext. To enable SSL set SSLEnabled 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:

If CleanSession is True, check the SessionPresent configuration setting once connected to determine whether the server actually had any session state saved.

Refer to CleanSession, SaveSession, and RestoreSession for more information about MQTT sessions and session state persistence; refer to WillTopic, WillMessage, WillQOS, and WillRetain for more information about MQTT Wills.

Basic Connection Example 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 not available at design time.

Firewall Property (MQTT Component)

A set of properties related to firewall access.

Syntax

public Firewall Firewall { get; set; }
Public Property Firewall As Firewall

Remarks

This is a Firewall type property which contains fields describing the firewall through which the component will attempt to connect.

IncomingMessages Property (MQTT Component)

Collection of incoming messages with QoS > 0 that have not been fully acknowledged.

Syntax

public MQTTMessageList IncomingMessages { get; }
Public ReadOnly Property IncomingMessages As MQTTMessageList

Remarks

Each time the component receives a message with a QoS of 1 or 2, it adds it to the IncomingMessages collection. A message remains in the IncomingMessages collection until the component has completed all of the acknowledgment steps required for it based on its QoS level.

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 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 event is fired.

The component processes messages anytime DoEvents is called. In applications with a GUI, the DoEvents method is also typically called automatically when the component is idle. In all other situations however, it is best practice to call DoEvents in a loop when possible to ensure timely processing of messages.

Note that incoming messages with a QoS of 0 are not added to IncomingMessages since they do not require acknowledgment. Upon receipt, they are added to an internal queue, and are fired through the MessageIn event as soon as DoEvents is called.

This collection is indexed from 0 to count -1.

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

KeepAliveInterval Property (MQTT Component)

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

Syntax

public int KeepAliveInterval { get; set; }
Public Property KeepAliveInterval As Integer

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 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.

LocalHost Property (MQTT Component)

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

Syntax

public string LocalHost { get; set; }
Public Property LocalHost As String

Default Value

""

Remarks

The LocalHost 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 multi-homed 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 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 multi-homed 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.

LocalPort Property (MQTT Component)

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

Syntax

public int LocalPort { get; set; }
Public Property LocalPort As Integer

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 in the client side.

OutgoingMessages Property (MQTT Component)

Collection of outgoing messages with QoS > 0 that have not been fully acknowledged.

Syntax

public MQTTMessageList OutgoingMessages { get; }
Public ReadOnly Property OutgoingMessages As MQTTMessageList

Remarks

Each time the component publishes a message with a QoS of 1 or 2, it adds it to the OutgoingMessages collection after the initial PUBLISH packet is sent (this does not occur for messages publish with a QoS of 0). A message remains in the OutgoingMessages collection until the component has completed all of the acknowledgment steps required for it based on its QoS level.

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 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 event is fired.

In MQTT 3.1.1, the 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.

The component processes messages anytime DoEvents is called. In applications with a GUI, the DoEvents method is also typically called automatically when the component is idle. In all other situations however, it is best practice to call DoEvents in a loop when possible to ensure timely processing of messages.

This collection is indexed from 0 to count -1.

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

Password Property (MQTT Component)

A password if authentication is to be used.

Syntax

public string Password { get; set; }
Public Property Password As String

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 may be specified without a Password, setting a Password without a User 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, allowing the field to be used for credentials other than a password.

This property is not available at design time.

ReadyToSend Property (MQTT Component)

Indicates whether the component is ready to send data.

Syntax

public bool ReadyToSend { get; }
Public ReadOnly Property ReadyToSend As Boolean

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 or PublishMessage fails due to a WOULDBLOCK condition.

Once data can be sent again, the ReadyToSend 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 will fire after the component completes any partially sent messages.

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

RemoteHost Property (MQTT Component)

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

Syntax

public string RemoteHost { get; set; }
Public Property RemoteHost As String

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 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.

RemotePort Property (MQTT Component)

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

Syntax

public int RemotePort { get; set; }
Public Property RemotePort As Integer

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.

SSLAcceptServerCert Property (MQTT Component)

Instructs the component to unconditionally accept the server certificate that matches the supplied certificate.

Syntax

public Certificate SSLAcceptServerCert { get; set; }
Public Property SSLAcceptServerCert As Certificate

Remarks

If it finds any issues with the certificate presented by the server, the component will normally terminate the connection with an error.

You may override this behavior by supplying a value for SSLAcceptServerCert. If the certificate supplied in SSLAcceptServerCert is the same as the certificate presented by the server, then the server certificate is accepted unconditionally, and the connection will continue normally.

Please note that this functionality is provided only for cases where you otherwise know that you are communicating with the right server. If used improperly, this property may create a security breach. Use it at your own risk.

SSLCert Property (MQTT Component)

The certificate to be used during SSL negotiation.

Syntax

public Certificate SSLCert { get; set; }
Public Property SSLCert As Certificate

Remarks

The digital certificate that the component will use during SSL negotiation. Set this property to a valid certificate before starting SSL negotiation. To set a certificate, you may set the Encoded field to the encoded certificate. To select a certificate, use the store and subject fields.

SSLEnabled Property (MQTT Component)

Whether TLS/SSL is enabled.

Syntax

public bool SSLEnabled { get; set; }
Public Property SSLEnabled As Boolean

Default Value

False

Remarks

This setting 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.

SSLProvider Property (MQTT Component)

This specifies the SSL/TLS implementation to use.

Syntax

public MqttSSLProviders SSLProvider { get; set; }

enum MqttSSLProviders { sslpAutomatic, sslpPlatform, sslpInternal }
Public Property SSLProvider As MqttSSLProviders

Enum MqttSSLProviders sslpAutomatic sslpPlatform sslpInternal End Enum

Default Value

0

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:

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, on Windows the component will use the platform implementation. On Linux/macOS the component will use the internal implementation. When TLS 1.3 is enabled via SSLEnabledProtocols the internal implementation is used on all platforms.

The async library does not support the platform implementation on Linux or macOS and will use the internal provider on those platforms.

The .NET Standard library will always use the internal implementation on all platforms.

SSLServerCert Property (MQTT Component)

The server certificate for the last established connection.

Syntax

public Certificate SSLServerCert { get; }
Public ReadOnly Property SSLServerCert As Certificate

Remarks

SSLServerCert contains the server certificate for the last established connection.

SSLServerCert is reset every time a new connection is attempted.

This property is read-only.

Timeout Property (MQTT Component)

A timeout for the component.

Syntax

public int Timeout { get; set; }
Public Property Timeout As Integer

Default Value

60

Remarks

This property defines the timeout when sending data. When SSLEnabled is False a value of 0 means data will be sent asynchronously and a positive value means data is sent synchronously. When SSLEnabled is True all data is sent synchronously regardless of the Timeout value. Please see the notes below for details.

Plaintext

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.

SSL

If the Timeout property is set to 0, all operations will run uninterrupted until successful completion or an error condition is encountered.

If Timeout is set to a positive value, the component will wait for the operation to complete before returning control.

Additional Notes

The component will use DoEvents 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 throws an exception.

Please note that by default, all timeouts are inactivity timeouts, i.e. 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.

User Property (MQTT Component)

A username if authentication is to be used.

Syntax

public string User { get; set; }
Public Property User As String

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, setting a Password without a User 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, allowing the field to be used for credentials other than a password.

This property is not available at design time.

Version Property (MQTT Component)

The MQTT protocol version that the component will conform to.

Syntax

public MqttVersions Version { get; set; }

enum MqttVersions { mvV3, mvV5 }
Public Property Version As MqttVersions

Enum MqttVersions mvV3 mvV5 End Enum

Default Value

0

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.

WillMessage Property (MQTT Component)

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

Syntax

public string WillMessage { get; set; }
Public Property WillMessage As String

Default Value

""

Remarks

This property may be set before calling Connect to specify to the server a message that should be published on WillTopic if the connection is closed ungracefully. Since it is sent to the server when Connect 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 is called if WillTopic is set.

Refer to WillTopic for more information about MQTT Will functionality.

This property is not available at design time.

WillTopic Property (MQTT Component)

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

Syntax

public string WillTopic { get; set; }
Public Property WillTopic As String

Default Value

""

Remarks

This property may be set before calling Connect to specify the topic name that the server should publish the WillMessage on if the connection is closed ungracefully. Since it is sent to the server when Connect 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 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 (in which case the server discards the Will message without publishing it). Note that in MQTT 5, the client can set a DisconnectReasonCode of 0x04 before calling Disconnect to instruct the server to publish the Will message anyway.

In addition to the WillTopic and WillMessage properties, the WillQOS setting may be used to specify the Will message's QoS level, and the 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 is called, the component will not send a Will to the server.

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

This property is not available at design time.

Config Method (MQTT Component)

Sets or retrieves a configuration setting.

Syntax

public string Config(string configurationString);

Async Version
public async Task<string> Config(string configurationString);
public async Task<string> Config(string configurationString, CancellationToken cancellationToken);
Public Function Config(ByVal ConfigurationString As String) As String

Async Version
Public Function Config(ByVal ConfigurationString As String) As Task(Of String)
Public Function Config(ByVal ConfigurationString As String, cancellationToken As CancellationToken) As Task(Of String)

Remarks

Config is a generic method available in every component. It is used to set and retrieve configuration settings 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, you must call Config("PROPERTY"). The value will be returned as a string.

Connect Method (MQTT Component)

Connects to the remote host.

Syntax

public void Connect();

Async Version
public async Task Connect();
public async Task Connect(CancellationToken cancellationToken);
Public Sub Connect()

Async Version
Public Sub Connect() As Task
Public Sub Connect(cancellationToken As CancellationToken) As Task

Remarks

This method connects to the remote host specified by RemoteHost and RemotePort. Calling this method is equivalent to setting the Connected property to True.

By default the component will connect in plaintext. To enable SSL set SSLEnabled 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:

If CleanSession is True, check the SessionPresent configuration setting once connected to determine whether the server actually had any session state saved.

Refer to CleanSession, SaveSession, and RestoreSession for more information about MQTT sessions and session state persistence; refer to WillTopic, WillMessage, WillQOS, and WillRetain for more information about MQTT Wills.

Basic Connection Example 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 Component)

Connects to the remote host.

Syntax

public void ConnectTo(string host, int port);

Async Version
public async Task ConnectTo(string host, int port);
public async Task ConnectTo(string host, int port, CancellationToken cancellationToken);
Public Sub ConnectTo(ByVal Host As String, ByVal Port As Integer)

Async Version
Public Sub ConnectTo(ByVal Host As String, ByVal Port As Integer) As Task
Public Sub ConnectTo(ByVal Host As String, ByVal Port As Integer, cancellationToken As CancellationToken) As Task

Remarks

This method connects to the remote host specified by the Host and Port parameters. Calling this method is equivalent to setting the RemoteHost property to Host, setting RemotePort to Port, and then setting the Connected property to True.

By default the component will connect in plaintext. To enable SSL set SSLEnabled 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:

If CleanSession is True, check the SessionPresent configuration setting once connected to determine whether the server actually had any session state saved.

Refer to CleanSession, SaveSession, and RestoreSession for more information about MQTT sessions and session state persistence; refer to WillTopic, WillMessage, WillQOS, and WillRetain for more information about MQTT Wills.

Basic Connection Example 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 Component)

This method disconnects from the remote host.

Syntax

public void Disconnect();

Async Version
public async Task Disconnect();
public async Task Disconnect(CancellationToken cancellationToken);
Public Sub Disconnect()

Async Version
Public Sub Disconnect() As Task
Public Sub Disconnect(cancellationToken As CancellationToken) As Task

Remarks

This method disconnects from the remote host. Calling this method is equivalent to setting the Connected property to False.

Refer to the Connected property for more information about MQTT-specific behavior.

DoEvents Method (MQTT Component)

Processes events from the internal message queue.

Syntax

public void DoEvents();

Async Version
public async Task DoEvents();
public async Task DoEvents(CancellationToken cancellationToken);
Public Sub DoEvents()

Async Version
Public Sub DoEvents() As Task
Public Sub DoEvents(cancellationToken As CancellationToken) As Task

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 Component)

Interrupt the current action and disconnects from the remote host.

Syntax

public void Interrupt();

Async Version
public async Task Interrupt();
public async Task Interrupt(CancellationToken cancellationToken);
Public Sub Interrupt()

Async Version
Public Sub Interrupt() As Task
Public Sub Interrupt(cancellationToken As CancellationToken) As Task

Remarks

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

PublishData Method (MQTT Component)

Publishes a message with a raw data payload.

Syntax

public void PublishData(string topic, int QOS, byte[] data);

Async Version
public async Task PublishData(string topic, int QOS, byte[] data);
public async Task PublishData(string topic, int QOS, byte[] data, CancellationToken cancellationToken);
Public Sub PublishData(ByVal Topic As String, ByVal QOS As Integer, ByVal Data As String)

Async Version
Public Sub PublishData(ByVal Topic As String, ByVal QOS As Integer, ByVal Data As String) As Task
Public Sub PublishData(ByVal Topic As String, ByVal QOS As Integer, ByVal Data As String, cancellationToken As CancellationToken) As Task

Remarks

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

Publish Examples // 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 configuration setting may be set before calling this method in order to publish a retained message (see 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 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).

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 LevelDescription
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 event is fired.
  4. The message is removed from OutgoingMessages.
  5. The MessageOut 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 event is fired.

In MQTT 3.1.1, the 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 - Set an integer alias along with the topic name when first publishing a message. When publishing additional messages to the same topic if 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 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 configuration setting for additional details.

PublishMessage Method (MQTT Component)

Publishes a message with a string payload.

Syntax

public void PublishMessage(string topic, int QOS, string message);

Async Version
public async Task PublishMessage(string topic, int QOS, string message);
public async Task PublishMessage(string topic, int QOS, string message, CancellationToken cancellationToken);
Public Sub PublishMessage(ByVal Topic As String, ByVal QOS As Integer, ByVal Message As String)

Async Version
Public Sub PublishMessage(ByVal Topic As String, ByVal QOS As Integer, ByVal Message As String) As Task
Public Sub PublishMessage(ByVal Topic As String, ByVal QOS As Integer, ByVal Message As String, cancellationToken As CancellationToken) As Task

Remarks

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

Publish Examples // 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 configuration setting may be set before calling this method in order to publish a retained message (see 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 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).

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 LevelDescription
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 event is fired.
  4. The message is removed from OutgoingMessages.
  5. The MessageOut 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 event is fired.

In MQTT 3.1.1, the 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 - Set an integer alias along with the topic name when first publishing a message. When publishing additional messages to the same topic if 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 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 configuration setting for additional details.

Reset Method (MQTT Component)

Reset the component.

Syntax

public void Reset();

Async Version
public async Task Reset();
public async Task Reset(CancellationToken cancellationToken);
Public Sub Reset()

Async Version
Public Sub Reset() As Task
Public Sub Reset(cancellationToken As CancellationToken) As Task

Remarks

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

RestoreSession Method (MQTT Component)

Restores session state data.

Syntax

public void RestoreSession(string stateData);

Async Version
public async Task RestoreSession(string stateData);
public async Task RestoreSession(string stateData, CancellationToken cancellationToken);
Public Sub RestoreSession(ByVal StateData As String)

Async Version
Public Sub RestoreSession(ByVal StateData As String) As Task
Public Sub RestoreSession(ByVal StateData As String, cancellationToken As CancellationToken) As Task

Remarks

This method restores previously-saved session state data and sets CleanSession to False. If the 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 to False, ClientId to the same value used in the initial connection, and call ConnectTo.

When the Connected event fires, query the SessionPresent configuration setting. If SessionPresent is True the session should be restored by calling RestoreSession. If 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.

Restore Session Example (Query SessionPresent) 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 to the value used in the initial connection, call RestoreSession, and then call ConnectTo.

Restore Session Example (Server Status Known) mqtt1.ClientId = clientId; mqtt1.RestoreSession(sessionStr); mqtt1.ConnectTo(host,port);

Refer to CleanSession and SaveSession for more information.

MQTT 5 Notes

In MQTT 5, the time after which the server discards saved session data is controlled by the 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 Component)

Saves session state data.

Syntax

public string SaveSession();

Async Version
public async Task<string> SaveSession();
public async Task<string> SaveSession(CancellationToken cancellationToken);
Public Function SaveSession() As String

Async Version
Public Function SaveSession() As Task(Of String)
Public Function SaveSession(cancellationToken As CancellationToken) As Task(Of String)

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 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 and RestoreSession for more information.

Subscribe Method (MQTT Component)

Subscribes the component to one or more topic filters.

Syntax

public void Subscribe(string topicFilter, int QOS);

Async Version
public async Task Subscribe(string topicFilter, int QOS);
public async Task Subscribe(string topicFilter, int QOS, CancellationToken cancellationToken);
Public Sub Subscribe(ByVal TopicFilter As String, ByVal QOS As Integer)

Async Version
Public Sub Subscribe(ByVal TopicFilter As String, ByVal QOS As Integer) As Task
Public Sub Subscribe(ByVal TopicFilter As String, ByVal QOS As Integer, cancellationToken As CancellationToken) As Task

Remarks

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

The Subscribed 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 event will fire as normal when doing this.

Subscribe Examples // 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 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 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 LevelDescription
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 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 methods. However, if it is necessary to verify that the feature is supported by the server, check the "SharedSubscriptionAvailable" value of the ConnAckProperties config.

Shared Subscription Example 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 equal to the ClientId 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:

    0Send retained messages at the time of the subscribe
    1Send retained messages at subscribe only if the subscription does not currently exist
    2Do 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, TopicRAPArray and 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.

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 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 configuration setting before calling Subscribe. To update the identifier, call Subscribe with a new SubscriptionIdentifier.

To verify that a server supports subscription identifiers, check the "SubscriptionIdentifiersAvailable" value in the 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 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 Component)

Unsubscribes the component from one or more topic filters.

Syntax

public void Unsubscribe(string topicFilter);

Async Version
public async Task Unsubscribe(string topicFilter);
public async Task Unsubscribe(string topicFilter, CancellationToken cancellationToken);
Public Sub Unsubscribe(ByVal TopicFilter As String)

Async Version
Public Sub Unsubscribe(ByVal TopicFilter As String) As Task
Public Sub Unsubscribe(ByVal TopicFilter As String, cancellationToken As CancellationToken) As Task

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 configuration setting (, by default).

The Unsubscribed 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 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 // 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 Component)

This event is fired immediately after a connection completes (or fails).

Syntax

public event OnConnectedHandler OnConnected;

public delegate void OnConnectedHandler(object sender, MqttConnectedEventArgs e);

public class MqttConnectedEventArgs : EventArgs {
  public int StatusCode { get; }
  public string Description { get; }
}
Public Event OnConnected As OnConnectedHandler

Public Delegate Sub OnConnectedHandler(sender As Object, e As MqttConnectedEventArgs)

Public Class MqttConnectedEventArgs Inherits EventArgs
  Public ReadOnly Property StatusCode As Integer
  Public ReadOnly Property Description As String
End Class

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 section for more information.

ConnectionStatus Event (MQTT Component)

This event is fired to indicate changes in the connection state.

Syntax

public event OnConnectionStatusHandler OnConnectionStatus;

public delegate void OnConnectionStatusHandler(object sender, MqttConnectionStatusEventArgs e);

public class MqttConnectionStatusEventArgs : EventArgs {
  public string ConnectionEvent { get; }
  public int StatusCode { get; }
  public string Description { get; }
}
Public Event OnConnectionStatus As OnConnectionStatusHandler

Public Delegate Sub OnConnectionStatusHandler(sender As Object, e As MqttConnectionStatusEventArgs)

Public Class MqttConnectionStatusEventArgs Inherits EventArgs
  Public ReadOnly Property ConnectionEvent As String
  Public ReadOnly Property StatusCode As Integer
  Public ReadOnly Property Description As String
End Class

Remarks

The ConnectionStatus 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 Component)

This event is fired when a connection is closed.

Syntax

public event OnDisconnectedHandler OnDisconnected;

public delegate void OnDisconnectedHandler(object sender, MqttDisconnectedEventArgs e);

public class MqttDisconnectedEventArgs : EventArgs {
  public int StatusCode { get; }
  public string Description { get; }
}
Public Event OnDisconnected As OnDisconnectedHandler

Public Delegate Sub OnDisconnectedHandler(sender As Object, e As MqttDisconnectedEventArgs)

Public Class MqttDisconnectedEventArgs Inherits EventArgs
  Public ReadOnly Property StatusCode As Integer
  Public ReadOnly Property Description As String
End Class

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 section for more information.

Error Event (MQTT Component)

Information about errors during data delivery.

Syntax

public event OnErrorHandler OnError;

public delegate void OnErrorHandler(object sender, MqttErrorEventArgs e);

public class MqttErrorEventArgs : EventArgs {
  public int ErrorCode { get; }
  public string Description { get; }
}
Public Event OnError As OnErrorHandler

Public Delegate Sub OnErrorHandler(sender As Object, e As MqttErrorEventArgs)

Public Class MqttErrorEventArgs Inherits EventArgs
  Public ReadOnly Property ErrorCode As Integer
  Public ReadOnly Property Description As String
End Class

Remarks

The Error event is fired in case of exceptional conditions during message processing. Normally the component throws an exception.

ErrorCode contains an error code and Description contains a textual description of the error. For a list of valid error codes and their descriptions, please refer to the Error Codes section.

Log Event (MQTT Component)

Fires once for each log message.

Syntax

public event OnLogHandler OnLog;

public delegate void OnLogHandler(object sender, MqttLogEventArgs e);

public class MqttLogEventArgs : EventArgs {
  public int LogLevel { get; }
  public string Message { get; }
  public string LogType { get; }
}
Public Event OnLog As OnLogHandler

Public Delegate Sub OnLogHandler(sender As Object, e As MqttLogEventArgs)

Public Class MqttLogEventArgs Inherits EventArgs
  Public ReadOnly Property LogLevel As Integer
  Public ReadOnly Property Message As String
  Public ReadOnly Property LogType As String
End Class

Remarks

This event fires once for each log message generated by the component. The verbosity is controlled by the 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 Component)

Fired when an incoming or outgoing message has completed all acknowledgment steps.

Syntax

public event OnMessageAckHandler OnMessageAck;

public delegate void OnMessageAckHandler(object sender, MqttMessageAckEventArgs e);

public class MqttMessageAckEventArgs : EventArgs {
  public int PacketId { get; }
  public int Direction { get; }
  public int Index { get; }
  public int ResponseCode { get; }
}
Public Event OnMessageAck As OnMessageAckHandler

Public Delegate Sub OnMessageAckHandler(sender As Object, e As MqttMessageAckEventArgs)

Public Class MqttMessageAckEventArgs Inherits EventArgs
  Public ReadOnly Property PacketId As Integer
  Public ReadOnly Property Direction As Integer
  Public ReadOnly Property Index As Integer
  Public ReadOnly Property ResponseCode As Integer
End Class

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 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 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 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 event is fired.

In MQTT 3.1.1, the 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 Component)

Fired when an incoming message has been received and/or fully acknowledged.

Syntax

public event OnMessageInHandler OnMessageIn;

public delegate void OnMessageInHandler(object sender, MqttMessageInEventArgs e);

public class MqttMessageInEventArgs : EventArgs {
  public int PacketId { get; }
  public string Topic { get; }
  public int QOS { get; }
  public string Message { get; }
public byte[] MessageB { get; } public bool Retained { get; } public bool Duplicate { get; } }
Public Event OnMessageIn As OnMessageInHandler

Public Delegate Sub OnMessageInHandler(sender As Object, e As MqttMessageInEventArgs)

Public Class MqttMessageInEventArgs Inherits EventArgs
  Public ReadOnly Property PacketId As Integer
  Public ReadOnly Property Topic As String
  Public ReadOnly Property QOS As Integer
  Public ReadOnly Property Message As String
Public ReadOnly Property MessageB As Byte() Public ReadOnly Property Retained As Boolean Public ReadOnly Property Duplicate As Boolean End Class

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 for more information about QoS 1 and 2 message processing steps.

// 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 Component)

Fired when an outgoing message has been sent and/or fully acknowledged.

Syntax

public event OnMessageOutHandler OnMessageOut;

public delegate void OnMessageOutHandler(object sender, MqttMessageOutEventArgs e);

public class MqttMessageOutEventArgs : EventArgs {
  public int PacketId { get; }
  public string Topic { get; }
  public int QOS { get; }
  public string Message { get; }
public byte[] MessageB { get; } public bool Retained { get; } public bool Duplicate { get; } }
Public Event OnMessageOut As OnMessageOutHandler

Public Delegate Sub OnMessageOutHandler(sender As Object, e As MqttMessageOutEventArgs)

Public Class MqttMessageOutEventArgs Inherits EventArgs
  Public ReadOnly Property PacketId As Integer
  Public ReadOnly Property Topic As String
  Public ReadOnly Property QOS As Integer
  Public ReadOnly Property Message As String
Public ReadOnly Property MessageB As Byte() Public ReadOnly Property Retained As Boolean Public ReadOnly Property Duplicate As Boolean End Class

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 for more information about QoS 1 and 2 message processing steps.

// 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 Component)

Fired when the component is ready to send data.

Syntax

public event OnReadyToSendHandler OnReadyToSend;

public delegate void OnReadyToSendHandler(object sender, MqttReadyToSendEventArgs e);

public class MqttReadyToSendEventArgs : EventArgs {
}
Public Event OnReadyToSend As OnReadyToSendHandler

Public Delegate Sub OnReadyToSendHandler(sender As Object, e As MqttReadyToSendEventArgs)

Public Class MqttReadyToSendEventArgs Inherits EventArgs
End Class

Remarks

The ReadyToSend event indicates that the underlying TCP/IP subsystem is ready to accept data after a call to PublishData or PublishMessage fails due to a WOULDBLOCK condition. The event is also fired immediately after a connection to the remote host is established.

SSLServerAuthentication Event (MQTT Component)

Fired after the server presents its certificate to the client.

Syntax

public event OnSSLServerAuthenticationHandler OnSSLServerAuthentication;

public delegate void OnSSLServerAuthenticationHandler(object sender, MqttSSLServerAuthenticationEventArgs e);

public class MqttSSLServerAuthenticationEventArgs : EventArgs {
  public string CertEncoded { get; }
public byte[] CertEncodedB { get; } public string CertSubject { get; } public string CertIssuer { get; } public string Status { get; } public bool Accept { get; set; } }
Public Event OnSSLServerAuthentication As OnSSLServerAuthenticationHandler

Public Delegate Sub OnSSLServerAuthenticationHandler(sender As Object, e As MqttSSLServerAuthenticationEventArgs)

Public Class MqttSSLServerAuthenticationEventArgs Inherits EventArgs
  Public ReadOnly Property CertEncoded As String
Public ReadOnly Property CertEncodedB As Byte() Public ReadOnly Property CertSubject As String Public ReadOnly Property CertIssuer As String Public ReadOnly Property Status As String Public Property Accept As Boolean End Class

Remarks

This event is where the client can decide whether to continue with the connection process or not. 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 to continue or not.

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 Component)

Shows the progress of the secure connection.

Syntax

public event OnSSLStatusHandler OnSSLStatus;

public delegate void OnSSLStatusHandler(object sender, MqttSSLStatusEventArgs e);

public class MqttSSLStatusEventArgs : EventArgs {
  public string Message { get; }
}
Public Event OnSSLStatus As OnSSLStatusHandler

Public Delegate Sub OnSSLStatusHandler(sender As Object, e As MqttSSLStatusEventArgs)

Public Class MqttSSLStatusEventArgs Inherits EventArgs
  Public ReadOnly Property Message As String
End Class

Remarks

The event is fired for informational and logging purposes only. Used to track the progress of the connection.

Subscribed Event (MQTT Component)

Fires for each topic filter subscription the server acknowledges.

Syntax

public event OnSubscribedHandler OnSubscribed;

public delegate void OnSubscribedHandler(object sender, MqttSubscribedEventArgs e);

public class MqttSubscribedEventArgs : EventArgs {
  public string TopicFilter { get; }
  public int QOS { get; }
  public int ResponseCode { get; }
}
Public Event OnSubscribed As OnSubscribedHandler

Public Delegate Sub OnSubscribedHandler(sender As Object, e As MqttSubscribedEventArgs)

Public Class MqttSubscribedEventArgs Inherits EventArgs
  Public ReadOnly Property TopicFilter As String
  Public ReadOnly Property QOS As Integer
  Public ReadOnly Property ResponseCode As Integer
End Class

Remarks

This event fires each time the server has acknowledged a topic filter subscription request (that is, calling Subscribe 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 Component)

Fires when the server has acknowledged an unsubscribe request.

Syntax

public event OnUnsubscribedHandler OnUnsubscribed;

public delegate void OnUnsubscribedHandler(object sender, MqttUnsubscribedEventArgs e);

public class MqttUnsubscribedEventArgs : EventArgs {
  public string TopicFilters { get; }
  public int ResponseCode { get; }
}
Public Event OnUnsubscribed As OnUnsubscribedHandler

Public Delegate Sub OnUnsubscribedHandler(sender As Object, e As MqttUnsubscribedEventArgs)

Public Class MqttUnsubscribedEventArgs Inherits EventArgs
  Public ReadOnly Property TopicFilters As String
  Public ReadOnly Property ResponseCode As Integer
End Class

Remarks

This event fires when the server has acknowledged an unsubscribe request sent with Unsubscribe (that is, unlike the Subscribed event, this event fires only once for each call to Unsubscribe, 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 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.

Certificate Type

This is the digital certificate being used.

Remarks

This type describes the current digital certificate. The certificate may be a public or private key. The fields are used to identify or select certificates.

Fields

EffectiveDate
String

This is the date on which this certificate becomes valid. Before this date, it is not valid. The following example illustrates the format of an encoded date:

23-Jan-2000 15:00:00.

Encoded
String

This is the certificate (PEM/base64 encoded). This field is used to assign a specific certificate. The Store and Subject fields also may be used to specify a certificate.

When Encoded is set, a search is initiated in the current Store for the private key of the certificate. If the key is found, Subject is updated to reflect the full subject of the selected certificate; otherwise, Subject is set to an empty string.

EncodedB
Byte []

This is the certificate (PEM/base64 encoded). This field is used to assign a specific certificate. The Store and Subject fields also may be used to specify a certificate.

When Encoded is set, a search is initiated in the current Store for the private key of the certificate. If the key is found, Subject is updated to reflect the full subject of the selected certificate; otherwise, Subject is set to an empty string.

ExpirationDate
String

This is the date the certificate expires. After this date, the certificate will no longer be valid. The following example illustrates the format of an encoded date:

23-Jan-2001 15:00:00.

ExtendedKeyUsage
String

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

Fingerprint
String

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

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

FingerprintSHA1
String

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

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

FingerprintSHA256
String

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

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

Issuer
String

This is the issuer of the certificate. This field contains a string representation of the name of the issuing authority for the certificate.

PrivateKey
String

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

Note: The PrivateKey may be available but not exportable. In this case, PrivateKey returns an empty string.

PrivateKeyAvailable
Boolean

This field shows whether a PrivateKey is available for the selected certificate. If PrivateKeyAvailable is True, the certificate may be used for authentication purposes (e.g., server authentication).

PrivateKeyContainer
String

This is the name of the PrivateKey container for the certificate (if available). This functionality is available only on Windows platforms.

PublicKey
String

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

PublicKeyAlgorithm
String

This field contains 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.

PublicKeyLength
Integer

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

SerialNumber
String

This is 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.

SignatureAlgorithm
String

The field contains 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.

Store
String

This is the name of the certificate store for the client certificate.

The StoreType field denotes the type of the certificate store specified by Store. If the store is password protected, specify the password in StorePassword.

Store is used in conjunction with the Subject field to specify client certificates. If Store has a value, and Subject or Encoded is set, a search for a certificate is initiated. Please see the Subject field for details.

Designations of certificate stores are platform-dependent.

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

MYA certificate store holding personal certificates with their associated private keys.
CACertifying authority certificates.
ROOTRoot certificates.

When the certificate store type is PFXFile, this property must be set to the name of the file. When the type is PFXBlob, the property must be set to the binary contents of a PFX file (i.e. PKCS12 certificate store).

StoreB
Byte []

This is the name of the certificate store for the client certificate.

The StoreType field denotes the type of the certificate store specified by Store. If the store is password protected, specify the password in StorePassword.

Store is used in conjunction with the Subject field to specify client certificates. If Store has a value, and Subject or Encoded is set, a search for a certificate is initiated. Please see the Subject field for details.

Designations of certificate stores are platform-dependent.

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

MYA certificate store holding personal certificates with their associated private keys.
CACertifying authority certificates.
ROOTRoot certificates.

When the certificate store type is PFXFile, this property must be set to the name of the file. When the type is PFXBlob, the property must be set to the binary contents of a PFX file (i.e. PKCS12 certificate store).

StorePassword
String

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

StoreType
CertStoreTypes

This is 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 field can take one of the following values:

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 (PKCS12) file containing certificates.
3 (cstPFXBlob)The certificate store is a string (binary or base64-encoded) representing a certificate store in PFX (PKCS12) 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 PKCS7 file containing certificates.
12 (cstP7BBlob)The certificate store is a string (binary) representing a certificate store in PKCS7 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).
20 (cstSecurityKey)The certificate is present on a physical security key accessible via a PKCS11 interface.

To use a security key the necessary data must first be collected using the CertMgr component. The ListStoreCertificates method may be called after setting CertStoreType to cstSecurityKey, CertStorePassword to the PIN, and CertStore to the full path of the PKCS11 dll. The certificate information returned in the CertList event's CertEncoded parameter may be saved for later use.

When using a certificate, pass the previously saved security key information as the Store and set StorePassword to the PIN.

Code Example: SSH Authentication with Security Key certmgr.CertStoreType = CertStoreTypes.cstSecurityKey; 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.cstSecurityKey, secKeyBlob, "123456", "*"); sftp.SSHUser = "test"; sftp.SSHLogon("myhost", 22);

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.
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.

Subject
String

This is the subject of the certificate used for client authentication.

This field will be populated with the full subject of the loaded certificate. When loading a certificate the subject is used to locate the certificate in the store.

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=support@nsoftware.com". Common fields and their meanings are displayed below.

FieldMeaning
CNCommon Name. This is commonly a host name like www.server.com.
OOrganization
OUOrganizational Unit
LLocality
SState
CCountry
EEmail Address

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

SubjectAltNames
String

This field contains comma-separated lists of alternative subject names for the certificate.

ThumbprintMD5
String

This field contains the MD5 hash of the certificate. If the hash does not already exist, it is computed.

ThumbprintSHA1
String

This field contains the SHA-1 hash of the certificate. If the hash does not already exist, it is computed.

ThumbprintSHA256
String

This field contains the SHA-256 hash of the certificate. If the hash does not already exist, it is computed.

Usage
String

This field contains the text description of UsageFlags.

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

  • Digital Signatures
  • Key Authentication
  • Key Encryption
  • Data Encryption
  • Key Agreement
  • Certificate Signing
  • Key Signing

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

UsageFlags
Integer

This field contains the flags that show intended use for the certificate. The value of UsageFlags is a combination of the following flags:

0x80Digital Signatures
0x40Key Authentication
0x20Key Encryption
0x10Data Encryption
0x08Key Agreement
0x04Certificate Signing
0x02Key Signing

Please see the Usage field for a text representation of UsageFlags.

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

Version
String

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

Constructors

public Certificate();
Public Certificate()

Creates a Certificate instance whose properties can be set. This is useful for use with CERTMGR when generating new certificates.

public Certificate( certificateFile);
Public Certificate(ByVal CertificateFile As )

Opens CertificateFile and reads out the contents as an X509 public key.

public Certificate( certificateData);
Public Certificate(ByVal CertificateData As Byte())

Parses CertificateData as an X509 public key.

public Certificate( certStoreType,  store,  storePassword,  subject);
Public Certificate(ByVal CertStoreType As , ByVal Store As , ByVal StorePassword As , ByVal Subject As )

CertStoreType identifies the type of certificate store to use. See StoreType for descriptions of the different certificate stores. Store is a file containing the certificate store. StorePassword is the password used to protect the store. After the store has been successfully opened, the component will attempt to find the certificate identified by Subject . This can be either a complete or a substring match of the X509 certificate's subject Distinguished Name (DN).

public Certificate( certStoreType,  store,  storePassword,  subject,  configurationString);
Public Certificate(ByVal CertStoreType As , ByVal Store As , ByVal StorePassword As , ByVal Subject As , ByVal ConfigurationString As )

CertStoreType identifies the type of certificate store to use. See StoreType for descriptions of the different certificate stores. Store is a file containing the certificate store. StorePassword is the password used to protect the store. ConfigurationString is a newline separated list of name-value pairs that may be used to modify the default behavior. Possible values include "PersistPFXKey", which shows whether or not the PFX key is persisted after performing operations with the private key. This correlates to the PKCS12_NO_PERSIST_KEY CyrptoAPI option. The default value is True (the key is persisted). "Thumbprint" - a MD5, SHA1, or SHA256 thumbprint of the certificate to load. When specified, this value is used to select the certificate in the store. This is applicable to cstUser, cstMachine, cstPublicKeyFile, and cstPFXFile store types. "UseInternalSecurityAPI" shows whether the platform (default) or the internal security API is used when performing certificate-related operations. After the store has been successfully opened, the component will attempt to find the certificate identified by Subject . This can be either a complete or a substring match of the X509 certificate's subject Distinguished Name (DN).

public Certificate( certStoreType,  store,  storePassword,  encoded);
Public Certificate(ByVal CertStoreType As , ByVal Store As , ByVal StorePassword As , ByVal Encoded As Byte())

CertStoreType identifies the type of certificate store to use. See StoreType for descriptions of the different certificate stores. Store is a file containing the certificate store. StorePassword is the password used to protect the store. After the store has been successfully opened, the component will load Encoded as an X509 certificate and search the opened store for a corresponding private key.

public Certificate( certStoreType,  storeBlob,  storePassword,  subject);
Public Certificate(ByVal CertStoreType As , ByVal StoreBlob As Byte(), ByVal StorePassword As , ByVal Subject As )

CertStoreType identifies the type of certificate store to use. See StoreType for descriptions of the different certificate stores. StoreBlob is a string (binary- or base64-encoded) containing the certificate data. StorePassword is the password used to protect the store. After the store has been successfully opened, the component will attempt to find the certificate identified by Subject . This can be either a complete or a substring match of the X509 certificate's subject Distinguished Name (DN).

public Certificate( certStoreType,  storeBlob,  storePassword,  subject,  configurationString);
Public Certificate(ByVal CertStoreType As , ByVal StoreBlob As Byte(), ByVal StorePassword As , ByVal Subject As , ByVal ConfigurationString As )

CertStoreType identifies the type of certificate store to use. See StoreType for descriptions of the different certificate stores. StoreBlob is a string (binary- or base64-encoded) containing the certificate data. StorePassword is the password used to protect the store. After the store has been successfully opened, the component will attempt to find the certificate identified by Subject . This can be either a complete or a substring match of the X509 certificate's subject Distinguished Name (DN).

public Certificate( certStoreType,  storeBlob,  storePassword,  encoded);
Public Certificate(ByVal CertStoreType As , ByVal StoreBlob As Byte(), ByVal StorePassword As , ByVal Encoded As Byte())

CertStoreType identifies the type of certificate store to use. See StoreType for descriptions of the different certificate stores. Store is a string (binary- or base64-encoded) containing the certificate store. StorePassword is the password used to protect the store. After the store has been successfully opened, the component will load Encoded as an X509 certificate and search the opened store for a corresponding private key.

Firewall Type

This is the firewall the component will connect through.

Remarks

When connecting through a firewall, this type is used to specify different properties of the firewall, such as the firewall Host and the FirewallType.

Fields

AutoDetect
Boolean

This field tells the component whether or not to automatically detect and use firewall system settings, if available.

FirewallType
FirewallTypes

This field determines 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. Port is set to 80.
fwSOCKS4 (2)Connect through a SOCKS4 Proxy. Port is set to 1080.
fwSOCKS5 (3)Connect through a SOCKS5 Proxy. Port is set to 1080.
fwSOCKS4A (10)Connect through a SOCKS4A Proxy. Port is set to 1080.

Host
String

This field contains the name or IP address of firewall (optional). If a Host is given, the requested connections will be authenticated through the specified firewall when connecting.

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

Password
String

This field contains a password if authentication is to be used when connecting through the firewall. If Host is specified, the User and Password fields are used to connect and authenticate to the given firewall. If the authentication fails, the component throws an exception.

Port
Integer

This field contains the transmission control protocol (TCP) port for the firewall Host. See the description of the Host field for details.

Note: This field is set automatically when FirewallType is set to a valid value. See the description of the FirewallType field for details.

User
String

This field contains a user name if authentication is to be used connecting through a firewall. If the Host is specified, this field and Password fields are used to connect and authenticate to the given Firewall. If the authentication fails, the component throws an exception.

Constructors

public Firewall();
Public Firewall()

MQTTMessage Type

An MQTT message.

Remarks

This type represents an MQTT message.

Fields

ContentType
String

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

Valid only for MQTT 5.

CorrelationData
String

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.

Duplicate
Boolean

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

Message
String

This message's raw data payload.

MessageB
Byte []

This message's raw data payload.

MessageExpInterval
Integer

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.

PacketId
Integer

This message's packet Id.

PayloadFormatIndicator
Integer

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

ValueDescription
0 Payload is unspecified bytes
1 Payload is UTF-8 Encoded Character Data

Valid only for MQTT 5.

QoS
Integer

This message's QoS level. Possible values are:

ValueDescription
0At most once delivery
1At least once delivery
2Exactly once delivery

ResponseTopic
String

String used as the topic name for a response message.

Valid only for MQTT 5.

Retained
Boolean

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

State
Integer

This message's current state.

Possible Outgoing Message States:

ValueDescription
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:

ValueDescription
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

SubscriptionIdentifiers
String

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

This field is only applicable to incoming messages.

If 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 method for more details.

Valid only for MQTT 5.

Topic
String

This message's topic.

MQTT 5 Notes:

If this value is empty, the TopicAlias field holds the assigned alias for the topic.

If this value is not empty and TopicAlias is non-zero,

TopicAlias
Integer

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 Topic string is empty.

For details on setting topic aliases for outgoing messages, see the TopicAlias configuration setting.

Valid only for MQTT 5.

Config Settings (MQTT 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 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. It is also available in the ConnectProperties config. See the 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 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.
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 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.
WildcardSubscriptionAvaiable 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 values, set the config JSON string to "".

Name Type Default Description
ClientTopicAliasMax Integer 0 See 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.

To set these values, set the ConnectProperties config to a string JSON object containing one or more key/value pairs to set. For example, to set all values:

{ 
  "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 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.

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 or PublishMessage. 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 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 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 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).
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.
TopicAlias Integer N/A See 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 config to a string JSON object containing one or more key/value pairs to set. For example:

{
  "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

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 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 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 is 60 seconds. Specify a 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.

To reset the value once it has been previously set, so that it is no longer included in future packets, set it to "".

ResponseTopic and Correlation Data are also accessible in the 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 or PublishMessage. 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 set to True.

MQTT 5 Notes

In MQTT 5, the "RetainAvailable" value in the 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 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, overriding this value. Additionally, the client may send a new value in the DisconnectProperties (as long as it was not 0 originally).

See CleanSession for more details on stored sessions in MQTT 5. This property also available in 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 is False when Connect is called, query this setting after the component connects to determine whether the server actually had data from a previous session.

If CleanSession is True when Connect 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 or RestoreSession 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 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 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 with the desired topic filter. Then, next time the client publishes a message to this topic, it may set TopicAlias to the value established and call PublishMessage 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. 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 config.

Code Example

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 and Unsubscribe 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 they were published from.

By default, this value is empty and all flags are False.

See the Subscribe 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 method, causing the component to ignore the QoS value passed to Subscribe. When doing this, the number of QoS values set to this setting must match the number of topic filters passed to Subscribe.

If this setting is set to the empty string (default) when Subscribe is called with multiple topic filters, the component will use the QoS value passed to Subscribe 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 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 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 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.
ReponseTopic 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.

Note that these values will be ignored if WillTopic is empty.

To set these values, set the ConnectProperties config to a string JSON object containing one or more key/value pairs to set. For example, to set all values:

{
"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 is set to a non-empty string when Connect 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 is empty.)

Refer to WillTopic for more information.

WillRetain:   Whether the server should retain the Will message after publishing it.

If WillTopic is set to a non-empty string when Connect 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 is empty.)

See Retain for general information about how retained messages are handled by the server.

Refer to WillTopic for more information.

TCPClient Config Settings

CloseStreamAfterTransfer:   If true, the component will close the upload or download stream after the transfer.

This setting determines whether the input or output stream is closed after the transfer completes. When set to True (default), all streams will be closed after a transfer is completed. In order to keep streams open after the transfer of data, set this to False. the default value is True.

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 for establishing a connection and transmitting/receiving data.

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 is given, requested connections will be authenticated through the specified firewall when connecting.

If the FirewallHost setting is set to a Domain Name, a DNS request is initiated. Upon successful termination of the request, the 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.

FirewallListener:   If true, the component binds to a SOCKS firewall as a server (TCPClient only).

This entry is for TCPClient only and does not work for other components that descend from TCPClient.

If this entry is set, the component acts as a server. RemoteHost and RemotePort are used to tell the SOCKS firewall in which address and port to listen to. The firewall rules may ignore RemoteHost, and it is recommended that RemoteHost be set to empty string in this case.

RemotePort is the port in which the firewall will listen to. If set to 0, the firewall will select a random port. The binding (address and port) is provided through the ConnectionStatus event.

The connection to the firewall is made by calling the Connect method.

FirewallPassword:   Password to be used if authentication is to be used when connecting through the firewall.

If FirewallHost is specified, the FirewallUser and FirewallPassword settings are used to connect and authenticate to the given firewall. If the authentication fails, the component throws 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 is set automatically when 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.

The appropriate values are as follows:

0No firewall (default setting).
1Connect through a tunneling proxy. FirewallPort is set to 80.
2Connect through a SOCKS4 Proxy. FirewallPort is set to 1080.
3Connect through a SOCKS5 Proxy. FirewallPort is set to 1080.
10Connect through a SOCKS4A Proxy. 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 is specified, the FirewallUser and FirewallPassword settings are used to connect and authenticate to the Firewall. If the authentication fails, the component throws 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 will automatically be set to True. A TCP keep-alive packet will be sent after a period of inactivity as defined by 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 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 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 is a positive value, the system will attempt to send pending data until the specified 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 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 multi-homed 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 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 multi-homed hosts (machines with more than one IP interface).

LocalPort:   The port in the local host where the component binds.

This 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 after the connection is established.

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

This; setting is useful when trying to connect to services that require a trusted port in 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 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 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 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 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.nsoftware.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 and 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 true, the socket will send all data that is ready to send at once. When false, the socket will send smaller buffered packets of data at small intervals. This is known as the Nagle algorithm.

By default, this config 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:

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 False and NTLM V1 will be used. Set this to True to use NTLM V2.

SSL Config Settings

CACertFilePaths:   The paths to CA certificate files when using Mono on Unix/Linux.

This setting specifies the paths on disk to CA certificate files when using Mono on Unix/Linux. It is not applicable in any other circumstances.

The value is formatted as a list of paths separated by semicolons. The component will check for the existence of each file in the order specified. When a file is found the CA certificates within the file will be loaded and used to determine the validity of server or client certificates.

The default value is:

/etc/ssl/ca-bundle.pem;/etc/pki/tls/certs/ca-bundle.crt;/etc/ssl/certs/ca-certificates.crt;/etc/pki/tls/cacert.pem

LogSSLPackets:   Controls whether SSL packets are logged when using the internal security API.

When SSLProvider is set to Internal, this setting controls whether SSL packets should be logged. By default, this setting is False, as it is only useful for debugging purposes.

When enabled, SSL packet logs are output using the SSLStatus event, which will fire each time an SSL packet is sent or received.

Enabling this setting has no effect if SSLProvider is set to Platform.

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 certificate to use during SSL client authentication.

This setting specifies one or more CA certificates to be included in the request when performing SSL client authentication. Some servers require the entire chain, including CA certificates, to be presented when performing SSL client authentication. The value of this setting is a newline (CrLf) separated list of certificates. For instance:

-----BEGIN CERTIFICATE-----
MIIEKzCCAxOgAwIBAgIRANTET4LIkxdH6P+CFIiHvTowDQYJKoZIhvcNAQELBQAw
...
eWHV5OW1K53o/atv59sOiW5K3crjFhsBOd5Q+cJJnU+SWinPKtANXMht+EDvYY2w
F0I1XhM+pKj7FjDr+XNj
-----END CERTIFICATE-----
\r \n
-----BEGIN CERTIFICATE-----
MIIEFjCCAv6gAwIBAgIQetu1SMxpnENAnnOz1P+PtTANBgkqhkiG9w0BAQUFADBp
..
d8q23djXZbVYiIfE9ebr4g3152BlVCHZ2GyPdjhIuLeH21VbT/dyEHHA
-----END CERTIFICATE-----

SSLCheckCRL:   Whether to check the Certificate Revocation List for the server certificate.

This setting specifies whether the component will check the Certificate Revocation List 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 throws 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 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 only supported in the Java, C#, and C++ editions. In the C++ edition, it is only supported on Windows operating systems.

SSLCipherStrength:   The minimum cipher strength used for bulk encryption.

This minimum cipher strength 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.

Please note that this setting contains the minimum cipher strength requested from the security library. The actual cipher strength used for the connection is shown by the SSLStatus event.

Use this 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 is currently not supported. This functionality is instead made available through the OpenSSLCipherList config setting.

SSLEnabledCipherSuites:   The cipher suite to be used in an SSL negotiation.

The enabled 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 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 is set to Platform: obj.config("SSLEnabledCipherSuites=*"); obj.config("SSLEnabledCipherSuites=CALG_AES_256"); obj.config("SSLEnabledCipherSuites=CALG_AES_256;CALG_3DES"); Possible values when SSLProvider is set to Platform include:

  • 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 is set to Internal: 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_DH_ANON_WITH_AES_128_CBC_SHA"); Possible values when SSLProvider is set to Internal include:
  • 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_DH_RSA_WITH_AES_128_GCM_SHA256 (Not Recommended)
  • TLS_DH_RSA_WITH_AES_256_GCM_SHA384 (Not Recommended)
  • TLS_DH_DSS_WITH_AES_128_GCM_SHA256 (Not Recommended)
  • TLS_DH_DSS_WITH_AES_256_GCM_SHA384 (Not Recommended)
  • 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) only the following cipher suites are supported:

  • TLS_AES_256_GCM_SHA384
  • TLS_CHACHA20_POLY1305_SHA256
  • TLS_AES_128_GCM_SHA256

SSLEnabledCipherSuites is used together with SSLCipherStrength.

SSLEnabledProtocols:   Used to enable/disable the supported security protocols.

Used to enable/disable the supported security protocols.

Not all supported protocols are enabled by default (the value of this setting is 4032). If you want more granular control over the enabled protocols, you can set this property to the binary 'OR' of one or more of the following values:

TLS1.312288 (Hex 3000)
TLS1.23072 (Hex C00) (Default)
TLS1.1768 (Hex 300) (Default)
TLS1 192 (Hex C0) (Default)
SSL3 48 (Hex 30)
SSL2 12 (Hex 0C)

SSLEnabledProtocols - TLS 1.3 Notes

By default when TLS 1.3 is enabled the component will use the internal TLS implementation.

In editions which are designed to run on Windows SSLProvider 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 only supported 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 only available on Windows 11 / Windows Server 2022 and up.
  • SSLEnabledCipherSuites and other similar SSL configuration settings are not supported.
  • If SSLEnabledProtocols includes both TLS 1.3 and TLS 1.2 the above 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.

SSLEnableRenegotiation:   Whether the renegotiation_info SSL extension is supported.

This setting specifies whether the renegotiation_info SSL extension will be used in the request when using the internal security API. This setting is true by default, but can be set to false to disable the extension.

This setting is only applicable when SSLProvider is set to Internal.

SSLIncludeCertChain:   Whether the entire certificate chain is included in the SSLServerAuthentication event.

This setting specifies whether the Encoded parameter of the SSLServerAuthentication 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 event.

If set to True all certificates returned by the server will be present in the Encoded parameter of the SSLServerAuthentication event. This includes the leaf certificate, any intermediate certificate, and the root certificate.

Note: When SSLProvider is set to Internal this value is automatically set to true. This is needed for proper validation when using the internal provider.

SSLKeyLogFile:   The location of a file where per-session secrets are written for debugging purposes.

This 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 traffice for debugging purposes. When writing to this file the component will only append, it will not overwrite previous values.

Note: This setting is only applicable when SSLProvider is set to Internal.

SSLNegotiatedCipher:   Returns the negotiated ciphersuite.

Returns the ciphersuite negotiated during the SSL handshake.

Note: For server components (e.g. TCPServer) this is a per-connection setting accessed by passing the ConnectionId. For example: server.Config("SSLNegotiatedCipher[connId]");

SSLNegotiatedCipherStrength:   Returns the negotiated ciphersuite strength.

Returns the strength of the ciphersuite negotiated during the SSL handshake.

Note: For server components (e.g.TCPServer) this is a per-connection setting accessed by passing the ConnectionId. For example: server.Config("SSLNegotiatedCipherStrength[connId]");

SSLNegotiatedCipherSuite:   Returns the negotiated ciphersuite.

Returns the ciphersuite negotiated during the SSL handshake represented as a single string.

Note: For server components (e.g. TCPServer) this is a per-connection setting accessed by passing the ConnectionId. For example: server.Config("SSLNegotiatedCipherSuite[connId]");

SSLNegotiatedKeyExchange:   Returns the negotiated key exchange algorithm.

Returns the key exchange algorithm negotiated during the SSL handshake.

Note: For server components (e.g. TCPServer) this is a per-connection setting accessed by passing the ConnectionId. For example: server.Config("SSLNegotiatedKeyExchange[connId]");

SSLNegotiatedKeyExchangeStrength:   Returns the negotiated key exchange algorithm strength.

Returns the strenghth of the key exchange algorithm negotiated during the SSL handshake.

Note: For server components (e.g. TCPServer) this is a per-connection setting accessed by passing the ConnectionId. For example: server.Config("SSLNegotiatedKeyExchangeStrength[connId]");

SSLNegotiatedVersion:   Returns the negotiated protocol version.

Returns the protocol version negotiated during the SSL handshake.

Note: For server components (e.g. TCPServer) this is a per-connection setting accessed by passing the ConnectionId. For example: server.Config("SSLNegotiatedVersion[connId]");

SSLSecurityFlags:   Flags that control certificate verification.

The following flags are defined (specified in hexadecimal notation). They can be or-ed together to exclude multiple conditions:

0x00000001Ignore time validity status of certificate.
0x00000002Ignore time validity status of CTL.
0x00000004Ignore non-nested certificate times.
0x00000010Allow unknown Certificate Authority.
0x00000020Ignore wrong certificate usage.
0x00000100Ignore unknown certificate revocation status.
0x00000200Ignore unknown CTL signer revocation status.
0x00000400Ignore unknown Certificate Authority revocation status.
0x00000800Ignore unknown Root revocation status.
0x00008000Allow test Root certificate.
0x00004000Trust test Root certificate.
0x80000000Ignore non-matching CN (certificate CN not-matching server name).

This functionality is currently not available in Java or when the provider is OpenSSL.

SSLServerCACerts:   A newline separated list of CA certificate to use during SSL server certificate validation.

This setting optionally specifies one or more CA certificates to be used when 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 setting should only be set 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 setting is a newline (CrLf) separated list of certificates. For instance:

-----BEGIN CERTIFICATE-----
MIIEKzCCAxOgAwIBAgIRANTET4LIkxdH6P+CFIiHvTowDQYJKoZIhvcNAQELBQAw
...
eWHV5OW1K53o/atv59sOiW5K3crjFhsBOd5Q+cJJnU+SWinPKtANXMht+EDvYY2w
F0I1XhM+pKj7FjDr+XNj
-----END CERTIFICATE-----
\r \n
-----BEGIN CERTIFICATE-----
MIIEFjCCAv6gAwIBAgIQetu1SMxpnENAnnOz1P+PtTANBgkqhkiG9w0BAQUFADBp
..
d8q23djXZbVYiIfE9ebr4g3152BlVCHZ2GyPdjhIuLeH21VbT/dyEHHA
-----END CERTIFICATE-----

TLS12SignatureAlgorithms:   Defines the allowed TLS 1.2 signature algorithms when SSLProvider is set to Internal.

This setting specifies the allowed server certificate signature algorithms when SSLProvider is set to Internal and 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 setting. If the server certificate signature algorithm is unsupported the component throws an exception.

The format of this value is a comma separated list of hash-signature combinations. For instance: TCPClient.SSLProvider = TCPClientSSLProviders.sslpInternal; TCPClient.Config("SSLEnabledProtocols=3072"); //TLS 1.2 TCPClient.Config("TLS12SignatureAlgorithms=sha256-rsa,sha256-dsa,sha1-rsa,sha1-dsa"); The default value for this 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.

In order to not restrict the server's certificate signature algorithm, specify an empty string as the value for this setting, which will cause the signature_algorithms TLS 1.2 extension to not be sent.

TLS12SupportedGroups:   The supported groups for ECC.

This 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 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 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 round trip 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 setting.

Note: All supported groups can always be used during the handshake even if not listed here, but if a group is used which is not present in this list it will incur an additional round trip and time to generate the key share for that group.

In most cases this setting does not need to be modified. This should only be modified 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 setting holds a comma separated list of allowed signature algorithms. Possible values are:

  • "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 setting is only applicable when SSLEnabledProtocols includes TLS 1.3.
TLS13SupportedGroups:   The supported groups for (EC)DHE key exchange.

This setting specifies a comma separated list of named groups used in TLS 1.3 for key exchange. This setting should only be modified 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

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)

Socket Config Settings

AbsoluteTimeout:   Determines whether timeouts are inactivity timeouts or absolute timeouts.

If AbsoluteTimeout is set to True, any method which does not complete within Timeout seconds will be aborted. By default, AbsoluteTimeout is False, and the timeout is an inactivity timeout.

Note: This option is not valid for 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 TCP/IP stack. You can increase or decrease its size depending on the amount of data that you will be receiving. Increasing the value of the InBufferSize setting can provide significant improvements in performance in some cases.

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. Increasing the value of the OutBufferSize setting can provide significant improvements in performance in some cases.

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.

Trappable Errors (MQTT 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. Error description contains 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   Can't 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 at this time. A connection is in progress.
101   You cannot change the RemoteHost (Server) at this time. A connection is in progress.
102   The RemoteHost 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 at this time. A connection is in progress.
107   You cannot change the LocalHost at this time. A connection is in progress.
112   You cannot change MaxLineLength at this time. A connection is in progress.
116   RemotePort 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.
303   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 non-socket.
10039   [10039] Destination address required.
10040   [10040] Message too long.
10041   [10041] Protocol wrong type for socket.
10042   [10042] Bad protocol option.
10043   [10043] Protocol not supported.
10044   [10044] Socket type not supported.
10045   [10045] Operation not supported on socket.
10046   [10046] Protocol family not supported.
10047   [10047] Address family not supported by protocol family.
10048   [10048] Address already in use.
10049   [10049] Can't 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] Can't send after socket shutdown.
10059   [10059] Too many references, can't splice.
10060   [10060] Connection timed out.
10061   [10061] Connection refused.
10062   [10062] Too many levels of symbolic links.
10063   [10063] File name too long.
10064   [10064] Host is down.
10065   [10065] No route to host.
10066   [10066] Directory 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 not loaded yet.
11001   [11001] Host not found.
11002   [11002] Non-authoritative 'Host not found' (try again or check DNS setup).
11003   [11003] Non-recoverable errors: FORMERR, REFUSED, NOTIMP.
11004   [11004] Valid name, no data record (check DNS setup).

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IPWorks MQ 2022 .NET Edition - Version 22.0 [Build 8369]