IPWorks IoT 2022 ActiveX Edition
Version 22.0 [Build 8369]

MQTT Control

Properties   Methods   Events   Config Settings   Errors  

A lightweight, fully-featured MQTT client implementation.

Syntax

MQTT

Remarks

The MQTT control provides a lightweight, fully-featured MQTT client implementation with support for versions 3.1.1 and 5.0. The control 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 control 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 control 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 control to the server.
ConnectedTriggers a connection or disconnection.
FirewallAutoDetectThis property tells the control whether or not to automatically detect and use firewall system settings, if available.
FirewallTypeThis property determines the type of firewall to connect through.
FirewallHostThis property contains the name or IP address of firewall (optional).
FirewallPasswordThis property contains a password if authentication is to be used when connecting through the firewall.
FirewallPortThis property contains the transmission control protocol (TCP) port for the firewall Host .
FirewallUserThis property contains a user name if authentication is to be used connecting through a firewall.
IncomingMessageCountThe number of records in the IncomingMessage arrays.
IncomingMessageContentTypeString describing the content of the message.
IncomingMessageCorrelationDataUsed by the sender of the request message to identify which request the response message is for when it is received.
IncomingMessageDuplicateWhether or not this message's Duplicate flag is set.
IncomingMessageMessageThis message's raw data payload.
IncomingMessageMessageExpIntervalThe lifetime of the message in seconds specified by the sender.
IncomingMessagePacketIdThis message's packet Id.
IncomingMessagePayloadFormatIndicatorIndicates whether the payload is unspecified bytes or UTF-8 Encoded character data.
IncomingMessageQoSThis message's QoS level.
IncomingMessageResponseTopicString used as the topic name for a response message.
IncomingMessageRetainedWhether or not this message's Retain flag is set.
IncomingMessageStateThis message's current state.
IncomingMessageSubscriptionIdentifiersA comma separated list of any SubscriptionIdentifiers associated with any client subscription(s) that caused this message to be delivered.
IncomingMessageTopicThis message's topic.
IncomingMessageTopicAliasAn integer used to identify the topic instead of the full topic filter in order to reduce the size of the publish packet.
KeepAliveIntervalThe maximum period of inactivity the control 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 control binds.
OutgoingMessageCountThe number of records in the OutgoingMessage arrays.
OutgoingMessageContentTypeString describing the content of the message.
OutgoingMessageCorrelationDataUsed by the sender of the request message to identify which request the response message is for when it is received.
OutgoingMessageDuplicateWhether or not this message's Duplicate flag is set.
OutgoingMessageMessageThis message's raw data payload.
OutgoingMessageMessageExpIntervalThe lifetime of the message in seconds specified by the sender.
OutgoingMessagePacketIdThis message's packet Id.
OutgoingMessagePayloadFormatIndicatorIndicates whether the payload is unspecified bytes or UTF-8 Encoded character data.
OutgoingMessageQoSThis message's QoS level.
OutgoingMessageResponseTopicString used as the topic name for a response message.
OutgoingMessageRetainedWhether or not this message's Retain flag is set.
OutgoingMessageStateThis message's current state.
OutgoingMessageSubscriptionIdentifiersA comma separated list of any SubscriptionIdentifiers associated with any client subscription(s) that caused this message to be delivered.
OutgoingMessageTopicThis message's topic.
OutgoingMessageTopicAliasAn integer used to identify the topic instead of the full topic filter in order to reduce the size of the publish packet.
PasswordA password if authentication is to be used.
ReadyToSendIndicates whether the control 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.
SSLAcceptServerCertEncodedThis is the certificate (PEM/base64 encoded).
SSLCertEncodedThis is the certificate (PEM/base64 encoded).
SSLCertStoreThis is the name of the certificate store for the client certificate.
SSLCertStorePasswordIf the type of certificate store requires a password, this property is used to specify the password needed to open the certificate store.
SSLCertStoreTypeThis is the type of certificate store for this certificate.
SSLCertSubjectThis is the subject of the certificate used for client authentication.
SSLEnabledWhether TLS/SSL is enabled.
SSLProviderThis specifies the SSL/TLS implementation to use.
SSLServerCertEncodedThis is the certificate (PEM/base64 encoded).
TimeoutA timeout for the control.
UserA username if authentication is to be used.
VersionThe MQTT protocol version that the control 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 control 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 control.
RestoreSessionRestores session state data.
SaveSessionSaves session state data.
SubscribeSubscribes the control to one or more topic filters.
UnsubscribeUnsubscribes the control from one or more topic filters.

Event List


The following is the full list of the events fired by the control 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 control 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 control 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.
ConnectionTimeoutSets a separate timeout value for establishing a connection.
FirewallAutoDetectTells the control whether or not to automatically detect and use firewall system settings, if available.
FirewallHostName or IP address of firewall (optional).
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 control 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.
LogSSLPacketsControls whether SSL packets are logged when using the internal security API.
OpenSSLCADirThe path to a directory containing CA certificates.
OpenSSLCAFileName of the file containing the list of CA's trusted by your application.
OpenSSLCipherListA string that controls the ciphers to be used by SSL.
OpenSSLPrngSeedDataThe data to seed the pseudo random number generator (PRNG).
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.
CodePageThe system code page used for Unicode to Multibyte translations.
UseInternalSecurityAPITells the control whether or not to use the system security libraries or an internal implementation.

CleanSession Property (MQTT Control)

Determines whether a clean session is used once connected.

Syntax

mqttcontrol.CleanSession[=boolean]

Default Value

True

Remarks

This property determines whether or not the control 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 control has connected successfully. In addition, the server will not save any state data when the control 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 control 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 control 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.

Data Type

Boolean

ClientId Property (MQTT Control)

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

Syntax

mqttcontrol.ClientId[=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 control is disconnected.

If ClientId is empty when Connect is called, the control's behavior depends on value of CleanSession. If CleanSession is True, the control will automatically generate a unique value for ClientId before connecting. If CleanSession is False, the control fails with an error.

This property is not available at design time.

Data Type

String

Connected Property (MQTT Control)

Triggers a connection or disconnection.

Syntax

mqttcontrol.Connected[=boolean]

Default Value

False

Remarks

This property triggers a connection or disconnection. Setting this property to True makes the control 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 control 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 control 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.

Data Type

Boolean

FirewallAutoDetect Property (MQTT Control)

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

Syntax

mqttcontrol.FirewallAutoDetect[=boolean]

Default Value

False

Remarks

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

Data Type

Boolean

FirewallType Property (MQTT Control)

This property determines the type of firewall to connect through.

Syntax

mqttcontrol.FirewallType[=integer]

Possible Values

fwNone(0), 
fwTunnel(1), 
fwSOCKS4(2), 
fwSOCKS5(3), 
fwSOCKS4A(10)

Default Value

0

Remarks

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

Data Type

Integer

FirewallHost Property (MQTT Control)

This property contains the name or IP address of firewall (optional).

Syntax

mqttcontrol.FirewallHost[=string]

Default Value

""

Remarks

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

If this property is set to a Domain Name, a DNS request is initiated. Upon successful termination of the request, this property is set to the corresponding address. If the search is not successful, the control fails with an error.

Data Type

String

FirewallPassword Property (MQTT Control)

This property contains a password if authentication is to be used when connecting through the firewall.

Syntax

mqttcontrol.FirewallPassword[=string]

Default Value

""

Remarks

This property contains a password if authentication is to be used when connecting through the firewall. If FirewallHost is specified, the FirewallUser and FirewallPassword properties are used to connect and authenticate to the given firewall. If the authentication fails, the control fails with an error.

Data Type

String

FirewallPort Property (MQTT Control)

This property contains the transmission control protocol (TCP) port for the firewall Host .

Syntax

mqttcontrol.FirewallPort[=integer]

Default Value

0

Remarks

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

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

Data Type

Integer

FirewallUser Property (MQTT Control)

This property contains a user name if authentication is to be used connecting through a firewall.

Syntax

mqttcontrol.FirewallUser[=string]

Default Value

""

Remarks

This property contains a user name if authentication is to be used connecting through a firewall. If the FirewallHost is specified, this property and FirewallPassword properties are used to connect and authenticate to the given Firewall. If the authentication fails, the control fails with an error.

Data Type

String

IncomingMessageCount Property (MQTT Control)

The number of records in the IncomingMessage arrays.

Syntax

mqttcontrol.IncomingMessageCount

Default Value

0

Remarks

This property controls the size of the following arrays:

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

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

Data Type

Integer

IncomingMessageContentType Property (MQTT Control)

String describing the content of the message.

Syntax

mqttcontrol.IncomingMessageContentType(IncomingMessageIndex)

Default Value

""

Remarks

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

Valid only for MQTT 5.

The IncomingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the IncomingMessageCount property.

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

Data Type

String

IncomingMessageCorrelationData Property (MQTT Control)

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

Syntax

mqttcontrol.IncomingMessageCorrelationData(IncomingMessageIndex)

Default Value

""

Remarks

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

Valid only for MQTT 5.

The IncomingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the IncomingMessageCount property.

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

Data Type

String

IncomingMessageDuplicate Property (MQTT Control)

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

Syntax

mqttcontrol.IncomingMessageDuplicate(IncomingMessageIndex)

Default Value

False

Remarks

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

The IncomingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the IncomingMessageCount property.

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

Data Type

Boolean

IncomingMessageMessage Property (MQTT Control)

This message's raw data payload.

Syntax

mqttcontrol.IncomingMessageMessage(IncomingMessageIndex)

Default Value

""

Remarks

This message's raw data payload.

The IncomingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the IncomingMessageCount property.

To read or write binary data to the property, a Variant (Byte Array) version is provided in .IncomingMessageMessageB.

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

Data Type

Binary String

IncomingMessageMessageExpInterval Property (MQTT Control)

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

Syntax

mqttcontrol.IncomingMessageMessageExpInterval(IncomingMessageIndex)

Default Value

0

Remarks

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

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

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

Valid only for MQTT 5.

The IncomingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the IncomingMessageCount property.

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

Data Type

Integer

IncomingMessagePacketId Property (MQTT Control)

This message's packet Id.

Syntax

mqttcontrol.IncomingMessagePacketId(IncomingMessageIndex)

Default Value

0

Remarks

This message's packet Id.

The IncomingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the IncomingMessageCount property.

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

Data Type

Integer

IncomingMessagePayloadFormatIndicator Property (MQTT Control)

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

Syntax

mqttcontrol.IncomingMessagePayloadFormatIndicator(IncomingMessageIndex)

Default Value

0

Remarks

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.

The IncomingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the IncomingMessageCount property.

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

Data Type

Integer

IncomingMessageQoS Property (MQTT Control)

This message's QoS level.

Syntax

mqttcontrol.IncomingMessageQoS(IncomingMessageIndex)

Default Value

0

Remarks

This message's QoS level. Possible values are:

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

The IncomingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the IncomingMessageCount property.

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

Data Type

Integer

IncomingMessageResponseTopic Property (MQTT Control)

String used as the topic name for a response message.

Syntax

mqttcontrol.IncomingMessageResponseTopic(IncomingMessageIndex)

Default Value

""

Remarks

String used as the topic name for a response message.

Valid only for MQTT 5.

The IncomingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the IncomingMessageCount property.

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

Data Type

String

IncomingMessageRetained Property (MQTT Control)

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

Syntax

mqttcontrol.IncomingMessageRetained(IncomingMessageIndex)

Default Value

False

Remarks

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

The IncomingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the IncomingMessageCount property.

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

Data Type

Boolean

IncomingMessageState Property (MQTT Control)

This message's current state.

Syntax

mqttcontrol.IncomingMessageState(IncomingMessageIndex)

Default Value

0

Remarks

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

The IncomingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the IncomingMessageCount property.

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

Data Type

Integer

IncomingMessageSubscriptionIdentifiers Property (MQTT Control)

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

Syntax

mqttcontrol.IncomingMessageSubscriptionIdentifiers(IncomingMessageIndex)

Default Value

""

Remarks

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

This property is only applicable to incoming messages.

If SubscriptionIdentifier 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.

The IncomingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the IncomingMessageCount property.

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

Data Type

String

IncomingMessageTopic Property (MQTT Control)

This message's topic.

Syntax

mqttcontrol.IncomingMessageTopic(IncomingMessageIndex)

Default Value

""

Remarks

This message's topic.

MQTT 5 Notes:

If this value is empty, the IncomingMessageTopicAlias property holds the assigned alias for the topic.

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

The IncomingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the IncomingMessageCount property.

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

Data Type

String

IncomingMessageTopicAlias Property (MQTT Control)

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

Syntax

mqttcontrol.IncomingMessageTopicAlias(IncomingMessageIndex)

Default Value

0

Remarks

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

If a non-zero topic alias is received, the client should establish a new topic alias mapping or use an existing mapping, depending on whether the IncomingMessageTopic string is empty.

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

Valid only for MQTT 5.

The IncomingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the IncomingMessageCount property.

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

Data Type

Integer

KeepAliveInterval Property (MQTT Control)

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

Syntax

mqttcontrol.KeepAliveInterval[=integer]

Default Value

0

Remarks

The KeepAliveInterval, if set to a non-zero value, is the maximum number of seconds that the control 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 control 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 control 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 control will not send any PINGREQ packets, and the server is not required to close the connection due to inactivity.

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

This property is not available at design time.

Data Type

Integer

LocalHost Property (MQTT Control)

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

Syntax

mqttcontrol.LocalHost[=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 control initiate connections (or accept in the case of server controls) only through that interface.

If the control 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.

Data Type

String

LocalPort Property (MQTT Control)

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

Syntax

mqttcontrol.LocalPort[=integer]

Default Value

0

Remarks

This property must be set before a connection is attempted. It instructs the control 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.

Data Type

Integer

OutgoingMessageCount Property (MQTT Control)

The number of records in the OutgoingMessage arrays.

Syntax

mqttcontrol.OutgoingMessageCount

Default Value

0

Remarks

This property controls the size of the following arrays:

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

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

Data Type

Integer

OutgoingMessageContentType Property (MQTT Control)

String describing the content of the message.

Syntax

mqttcontrol.OutgoingMessageContentType(OutgoingMessageIndex)

Default Value

""

Remarks

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

Valid only for MQTT 5.

The OutgoingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the OutgoingMessageCount property.

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

Data Type

String

OutgoingMessageCorrelationData Property (MQTT Control)

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

Syntax

mqttcontrol.OutgoingMessageCorrelationData(OutgoingMessageIndex)

Default Value

""

Remarks

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

Valid only for MQTT 5.

The OutgoingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the OutgoingMessageCount property.

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

Data Type

String

OutgoingMessageDuplicate Property (MQTT Control)

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

Syntax

mqttcontrol.OutgoingMessageDuplicate(OutgoingMessageIndex)

Default Value

False

Remarks

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

The OutgoingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the OutgoingMessageCount property.

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

Data Type

Boolean

OutgoingMessageMessage Property (MQTT Control)

This message's raw data payload.

Syntax

mqttcontrol.OutgoingMessageMessage(OutgoingMessageIndex)

Default Value

""

Remarks

This message's raw data payload.

The OutgoingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the OutgoingMessageCount property.

To read or write binary data to the property, a Variant (Byte Array) version is provided in .OutgoingMessageMessageB.

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

Data Type

Binary String

OutgoingMessageMessageExpInterval Property (MQTT Control)

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

Syntax

mqttcontrol.OutgoingMessageMessageExpInterval(OutgoingMessageIndex)

Default Value

0

Remarks

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

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

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

Valid only for MQTT 5.

The OutgoingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the OutgoingMessageCount property.

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

Data Type

Integer

OutgoingMessagePacketId Property (MQTT Control)

This message's packet Id.

Syntax

mqttcontrol.OutgoingMessagePacketId(OutgoingMessageIndex)

Default Value

0

Remarks

This message's packet Id.

The OutgoingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the OutgoingMessageCount property.

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

Data Type

Integer

OutgoingMessagePayloadFormatIndicator Property (MQTT Control)

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

Syntax

mqttcontrol.OutgoingMessagePayloadFormatIndicator(OutgoingMessageIndex)

Default Value

0

Remarks

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.

The OutgoingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the OutgoingMessageCount property.

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

Data Type

Integer

OutgoingMessageQoS Property (MQTT Control)

This message's QoS level.

Syntax

mqttcontrol.OutgoingMessageQoS(OutgoingMessageIndex)

Default Value

0

Remarks

This message's QoS level. Possible values are:

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

The OutgoingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the OutgoingMessageCount property.

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

Data Type

Integer

OutgoingMessageResponseTopic Property (MQTT Control)

String used as the topic name for a response message.

Syntax

mqttcontrol.OutgoingMessageResponseTopic(OutgoingMessageIndex)

Default Value

""

Remarks

String used as the topic name for a response message.

Valid only for MQTT 5.

The OutgoingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the OutgoingMessageCount property.

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

Data Type

String

OutgoingMessageRetained Property (MQTT Control)

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

Syntax

mqttcontrol.OutgoingMessageRetained(OutgoingMessageIndex)

Default Value

False

Remarks

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

The OutgoingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the OutgoingMessageCount property.

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

Data Type

Boolean

OutgoingMessageState Property (MQTT Control)

This message's current state.

Syntax

mqttcontrol.OutgoingMessageState(OutgoingMessageIndex)

Default Value

0

Remarks

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

The OutgoingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the OutgoingMessageCount property.

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

Data Type

Integer

OutgoingMessageSubscriptionIdentifiers Property (MQTT Control)

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

Syntax

mqttcontrol.OutgoingMessageSubscriptionIdentifiers(OutgoingMessageIndex)

Default Value

""

Remarks

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

This property is only applicable to incoming messages.

If SubscriptionIdentifier 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.

The OutgoingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the OutgoingMessageCount property.

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

Data Type

String

OutgoingMessageTopic Property (MQTT Control)

This message's topic.

Syntax

mqttcontrol.OutgoingMessageTopic(OutgoingMessageIndex)

Default Value

""

Remarks

This message's topic.

MQTT 5 Notes:

If this value is empty, the OutgoingMessageTopicAlias property holds the assigned alias for the topic.

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

The OutgoingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the OutgoingMessageCount property.

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

Data Type

String

OutgoingMessageTopicAlias Property (MQTT Control)

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

Syntax

mqttcontrol.OutgoingMessageTopicAlias(OutgoingMessageIndex)

Default Value

0

Remarks

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

If a non-zero topic alias is received, the client should establish a new topic alias mapping or use an existing mapping, depending on whether the OutgoingMessageTopic string is empty.

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

Valid only for MQTT 5.

The OutgoingMessageIndex parameter specifies the index of the item in the array. The size of the array is controlled by the OutgoingMessageCount property.

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

Data Type

Integer

Password Property (MQTT Control)

A password if authentication is to be used.

Syntax

mqttcontrol.Password[=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.

Data Type

String

ReadyToSend Property (MQTT Control)

Indicates whether the control is ready to send data.

Syntax

mqttcontrol.ReadyToSend

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 control 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 control completes any partially sent messages.

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

Data Type

Boolean

RemoteHost Property (MQTT Control)

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

Syntax

mqttcontrol.RemoteHost[=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 control 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 control 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.

Data Type

String

RemotePort Property (MQTT Control)

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

Syntax

mqttcontrol.RemotePort[=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.

Data Type

Integer

SSLAcceptServerCertEncoded Property (MQTT Control)

This is the certificate (PEM/base64 encoded).

Syntax

mqttcontrol.SSLAcceptServerCertEncoded[=string]

Default Value

""

Remarks

This is the certificate (PEM/base64 encoded). This property is used to assign a specific certificate. The SSLAcceptServerCertStore and SSLAcceptServerCertSubject properties also may be used to specify a certificate.

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

To read or write binary data to the property, a Variant (Byte Array) version is provided in .SSLAcceptServerCertEncodedB.

This property is not available at design time.

Data Type

Binary String

SSLCertEncoded Property (MQTT Control)

This is the certificate (PEM/base64 encoded).

Syntax

mqttcontrol.SSLCertEncoded[=string]

Default Value

""

Remarks

This is the certificate (PEM/base64 encoded). This property is used to assign a specific certificate. The SSLCertStore and SSLCertSubject properties also may be used to specify a certificate.

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

To read or write binary data to the property, a Variant (Byte Array) version is provided in .SSLCertEncodedB.

This property is not available at design time.

Data Type

Binary String

SSLCertStore Property (MQTT Control)

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

Syntax

mqttcontrol.SSLCertStore[=string]

Default Value

"MY"

Remarks

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

The SSLCertStoreType property denotes the type of the certificate store specified by SSLCertStore. If the store is password protected, specify the password in SSLCertStorePassword.

SSLCertStore is used in conjunction with the SSLCertSubject property to specify client certificates. If SSLCertStore has a value, and SSLCertSubject or SSLCertEncoded is set, a search for a certificate is initiated. Please see the SSLCertSubject property 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).

To read or write binary data to the property, a Variant (Byte Array) version is provided in .SSLCertStoreB.

Data Type

Binary String

SSLCertStorePassword Property (MQTT Control)

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

Syntax

mqttcontrol.SSLCertStorePassword[=string]

Default Value

""

Remarks

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

Data Type

String

SSLCertStoreType Property (MQTT Control)

This is the type of certificate store for this certificate.

Syntax

mqttcontrol.SSLCertStoreType[=integer]

Possible Values

cstUser(0), 
cstMachine(1), 
cstPFXFile(2), 
cstPFXBlob(3), 
cstJKSFile(4), 
cstJKSBlob(5), 
cstPEMKeyFile(6), 
cstPEMKeyBlob(7), 
cstPublicKeyFile(8), 
cstPublicKeyBlob(9), 
cstSSHPublicKeyBlob(10), 
cstP7BFile(11), 
cstP7BBlob(12), 
cstSSHPublicKeyFile(13), 
cstPPKFile(14), 
cstPPKBlob(15), 
cstXMLFile(16), 
cstXMLBlob(17), 
cstJWKFile(18), 
cstJWKBlob(19), 
cstSecurityKey(20), 
cstBCFKSFile(21), 
cstBCFKSBlob(22), 
cstAuto(99)

Default Value

0

Remarks

This is the type of certificate store for this certificate.

The control supports both public and private keys in a variety of formats. When the cstAuto value is used the control will automatically determine the type. This property 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 control. 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 SSLCertStore and set SSLCertStorePassword 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.

Data Type

Integer

SSLCertSubject Property (MQTT Control)

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

Syntax

mqttcontrol.SSLCertSubject[=string]

Default Value

""

Remarks

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

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

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

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

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

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

The certificate subject is a comma separated list of distinguished name fields and values. For instance "CN=www.server.com, OU=test, C=US, E=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.

Data Type

String

SSLEnabled Property (MQTT Control)

Whether TLS/SSL is enabled.

Syntax

mqttcontrol.SSLEnabled[=boolean]

Default Value

False

Remarks

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

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

This property is not available at design time.

Data Type

Boolean

SSLProvider Property (MQTT Control)

This specifies the SSL/TLS implementation to use.

Syntax

mqttcontrol.SSLProvider[=integer]

Possible Values

sslpAutomatic(0), 
sslpPlatform(1), 
sslpInternal(2)

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 control 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 control will select a provider depending on the current platform.

When Automatic is selected the platform implementation is used by default. When TLS 1.3 is enabled via SSLEnabledProtocols the internal implementation is used.

Data Type

Integer

SSLServerCertEncoded Property (MQTT Control)

This is the certificate (PEM/base64 encoded).

Syntax

mqttcontrol.SSLServerCertEncoded

Default Value

""

Remarks

This is the certificate (PEM/base64 encoded). This property is used to assign a specific certificate. The SSLServerCertStore and SSLServerCertSubject properties also may be used to specify a certificate.

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

To read or write binary data to the property, a Variant (Byte Array) version is provided in .SSLServerCertEncodedB.

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

Data Type

Binary String

Timeout Property (MQTT Control)

A timeout for the control.

Syntax

mqttcontrol.Timeout[=integer]

Default Value

60

Remarks

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

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

The control 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 control fails with an error.

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.

Data Type

Integer

User Property (MQTT Control)

A username if authentication is to be used.

Syntax

mqttcontrol.User[=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.

Data Type

String

Version Property (MQTT Control)

The MQTT protocol version that the control will conform to.

Syntax

mqttcontrol.Version[=integer]

Possible Values

mvV3(0), 
mvV5(1)

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.

Data Type

Integer

WillMessage Property (MQTT Control)

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

Syntax

mqttcontrol.WillMessage[=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.

Data Type

String

WillTopic Property (MQTT Control)

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

Syntax

mqttcontrol.WillTopic[=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 control 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.

Data Type

String

Config Method (MQTT Control)

Sets or retrieves a configuration setting.

Syntax

mqttcontrol.Config ConfigurationString

Remarks

Config is a generic method available in every control. It is used to set and retrieve configuration settings for the control.

These settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the control, 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 Control)

Connects to the remote host.

Syntax

mqttcontrol.Connect 

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 control 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 control 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 Control)

Connects to the remote host.

Syntax

mqttcontrol.ConnectTo Host, Port

Remarks

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

By default the control 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 control 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 Control)

This method disconnects from the remote host.

Syntax

mqttcontrol.Disconnect 

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 Control)

Processes events from the internal message queue.

Syntax

mqttcontrol.DoEvents 

Remarks

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

Interrupt Method (MQTT Control)

Interrupt the current action and disconnects from the remote host.

Syntax

mqttcontrol.Interrupt 

Remarks

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

PublishData Method (MQTT Control)

Publishes a message with a raw data payload.

Syntax

mqttcontrol.PublishData Topic, QOS, Data

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 control sends a PUBLISH packet, but does not add the message to OutgoingMessage* (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 control sends the PUBLISH packet, then adds the message to OutgoingMessage*.
  2. The control waits to receive a PUBACK (publish acknowledgment) packet.
  3. The MessageAck event is fired.
  4. The message is removed from OutgoingMessage*.
  5. The MessageOut event is fired.

Outgoing messages with a QoS of 2 follow these steps:

  1. The control sends the PUBLISH packet, then adds the message to OutgoingMessage*.
  2. The control waits to receive a PUBREC (publish received) packet.
  3. The control sends a PUBREL (publish release) packet in response.
  4. The control waits to receive a PUBCOMP (publish complete) packet.
  5. The MessageAck event is fired.
  6. The message is removed from OutgoingMessage*.
  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 control 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 Control)

Publishes a message with a string payload.

Syntax

mqttcontrol.PublishMessage Topic, QOS, Message

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 control sends a PUBLISH packet, but does not add the message to OutgoingMessage* (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 control sends the PUBLISH packet, then adds the message to OutgoingMessage*.
  2. The control waits to receive a PUBACK (publish acknowledgment) packet.
  3. The MessageAck event is fired.
  4. The message is removed from OutgoingMessage*.
  5. The MessageOut event is fired.

Outgoing messages with a QoS of 2 follow these steps:

  1. The control sends the PUBLISH packet, then adds the message to OutgoingMessage*.
  2. The control waits to receive a PUBREC (publish received) packet.
  3. The control sends a PUBREL (publish release) packet in response.
  4. The control waits to receive a PUBCOMP (publish complete) packet.
  5. The MessageAck event is fired.
  6. The message is removed from OutgoingMessage*.
  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 control 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 Control)

Reset the control.

Syntax

mqttcontrol.Reset 

Remarks

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

RestoreSession Method (MQTT Control)

Restores session state data.

Syntax

mqttcontrol.RestoreSession StateData

Remarks

This method restores previously-saved session state data and sets CleanSession to False. If the SessionStateFile configuration setting is set, the control 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 Control)

Saves session state data.

Syntax

mqttcontrol.SaveSession 

Remarks

This method saves session state data currently held by the control, returning it as a string that can later be used to restore it. If the SessionStateFile configuration setting is set, the control 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 Control)

Subscribes the control to one or more topic filters.

Syntax

mqttcontrol.Subscribe TopicFilter, QOS

Remarks

This method subscribes the control 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 control 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 control, 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 Control)

Unsubscribes the control from one or more topic filters.

Syntax

mqttcontrol.Unsubscribe TopicFilter

Remarks

This method unsubscribes the control 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 Control)

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

Syntax

Sub mqttcontrol_Connected(StatusCode As Integer, Description As String)

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. The corresponding Visual Basic error code can be obtained by adding 15001 to this value.

Please refer to the Error Codes section for more information.

ConnectionStatus Event (MQTT Control)

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

Syntax

Sub mqttcontrol_ConnectionStatus(ConnectionEvent As String, StatusCode As Integer, Description As String)

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. The corresponding Visual Basic error code can be obtained by adding 15001 to this value.

Disconnected Event (MQTT Control)

This event is fired when a connection is closed.

Syntax

Sub mqttcontrol_Disconnected(StatusCode As Integer, Description As String)

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. The corresponding Visual Basic error code can be obtained by adding 15001 to this value.

Please refer to the Error Codes section for more information.

Error Event (MQTT Control)

Information about errors during data delivery.

Syntax

Sub mqttcontrol_Error(ErrorCode As Integer, Description As String)

Remarks

The Error event is fired in case of exceptional conditions during message processing. Normally the control fails with an error.

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 Control)

Fires once for each log message.

Syntax

Sub mqttcontrol_Log(LogLevel As Integer, Message As String, LogType As String)

Remarks

This event fires once for each log message generated by the control. 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 control.
  • Packet: Packet content logging.
  • Reconnect: Reconnection status messages.
  • Session: Session status messages.

MessageAck Event (MQTT Control)

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

Syntax

Sub mqttcontrol_MessageAck(PacketId As Integer, Direction As Integer, Index As Integer, ResponseCode As Integer)

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 IncomingMessage* properties or OutgoingMessage* properties.
  • 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 IncomingMessage* when the control receives the PUBLISH packet.
  2. The control sends a PUBACK (publish acknowledgment) packet in response.
  3. The MessageAck event is fired.
  4. The message is removed from IncomingMessage*.
  5. The MessageIn event is fired.

Incoming messages with a QoS of 2 follow these steps:

  1. The message is added to IncomingMessage* when the control receives the PUBLISH packet.
  2. The control sends a PUBREC (publish received) packet in response.
  3. The control waits to receive a PUBREL (publish release) packet.
  4. The control sends a PUBCOMP (publish complete) packet in response.
  5. The MessageAck event is fired.
  6. The message is removed from IncomingMessage*.
  7. The MessageIn event is fired.

Outbound Message Processing

Outgoing messages with a QoS of 1 follow these steps:

  1. The control sends the PUBLISH packet, then adds the message to OutgoingMessage*.
  2. The control waits to receive a PUBACK (publish acknowledgment) packet.
  3. The MessageAck event is fired.
  4. The message is removed from OutgoingMessage*.
  5. The MessageOut event is fired.

Outgoing messages with a QoS of 2 follow these steps:

  1. The control sends the PUBLISH packet, then adds the message to OutgoingMessage*.
  2. The control waits to receive a PUBREC (publish received) packet.
  3. The control sends a PUBREL (publish release) packet in response.
  4. The control waits to receive a PUBCOMP (publish complete) packet.
  5. The MessageAck event is fired.
  6. The message is removed from OutgoingMessage*.
  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 control 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 Control)

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

Syntax

Sub mqttcontrol_MessageIn(PacketId As Integer, Topic As String, QOS As Integer, Message As String, Retained As Boolean, Duplicate As Boolean)

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 Control)

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

Syntax

Sub mqttcontrol_MessageOut(PacketId As Integer, Topic As String, QOS As Integer, Message As String, Retained As Boolean, Duplicate As Boolean)

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 Control)

Fired when the control is ready to send data.

Syntax

Sub mqttcontrol_ReadyToSend()

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 Control)

Fired after the server presents its certificate to the client.

Syntax

Sub mqttcontrol_SSLServerAuthentication(CertEncoded As String, CertSubject As String, CertIssuer As String, Status As String, Accept As Boolean)

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 Control)

Shows the progress of the secure connection.

Syntax

Sub mqttcontrol_SSLStatus(Message As String)

Remarks

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

Subscribed Event (MQTT Control)

Fires for each topic filter subscription the server acknowledges.

Syntax

Sub mqttcontrol_Subscribed(TopicFilter As String, QOS As Integer, ResponseCode As Integer)

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 Control)

Fires when the server has acknowledged an unsubscribe request.

Syntax

Sub mqttcontrol_Unsubscribed(TopicFilters As String, ResponseCode As Integer)

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.

Config Settings (MQTT Control)

The control 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 control, 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 control 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 control 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 control 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 control 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 control 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 control 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 control 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 control 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 control 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 control 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 control 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 control 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 control 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 control 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 control 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 control 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

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 control will use Timeout for establishing a connection and transmitting/receiving data.

FirewallAutoDetect:   Tells the control whether or not to automatically detect and use firewall system settings, if available.

This configuration setting is provided for use by controls 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 controls that do not directly expose Firewall properties.

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 control fails with an error.

Note: This setting is provided for use by controls 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 controls 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 controls 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 control fails with an error.

Note: This setting is provided for use by controls 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 control 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 control initiate connections (or accept in the case of server controls) only through that interface.

If the control 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 control binds.

This must be set before a connection is attempted. It instructs the control 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 control will use IPv4 exclusively. When set to 1, the control will use IPv6 exclusively. To instruct the control 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

SSL Config Settings

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.

OpenSSLCADir:   The path to a directory containing CA certificates.

This functionality is available only when the provider is OpenSSL.

The path set by this property should point to a directory containing CA certificates in PEM format. The files each contain one CA certificate. The files are looked up by the CA subject name hash value, which must hence be available. If more than one CA certificate with the same name hash value exist, the extension must be different (e.g. 9d66eef0.0, 9d66eef0.1 etc). OpenSSL recommends to use the c_rehash utility to create the necessary links. Please refer to the OpenSSL man page SSL_CTX_load_verify_locations(3) for details.

OpenSSLCAFile:   Name of the file containing the list of CA's trusted by your application.

This functionality is available only when the provider is OpenSSL.

The file set by this property should contain a list of CA certificates in PEM format. The file can contain several CA certificates identified by

-----BEGIN CERTIFICATE-----

... (CA certificate in base64 encoding) ...

-----END CERTIFICATE-----

sequences. Before, between, and after the certificates text is allowed which can be used e.g. for descriptions of the certificates. Please refer to the OpenSSL man page SSL_CTX_load_verify_locations(3) for details.

OpenSSLCipherList:   A string that controls the ciphers to be used by SSL.

This functionality is available only when the provider is OpenSSL.

The format of this string is described in the OpenSSL man page ciphers(1) section "CIPHER LIST FORMAT". Please refer to it for details. The default string "DEFAULT" is determined at compile time and is normally equivalent to "ALL:!ADH:RC4+RSA:+SSLv2:@STRENGTH".

OpenSSLPrngSeedData:   The data to seed the pseudo random number generator (PRNG).

This functionality is available only when the provider is OpenSSL.

By default OpenSSL uses the device file "/dev/urandom" to seed the PRNG and setting OpenSSLPrngSeedData is not required. If set, the string specified is used to seed the PRNG.

ReuseSSLSession:   Determines if the SSL session is reused.

If set to true, the control 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 control 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 control will check the Certificate Revocation List specified by the server certificate. If set to 1 or 2, the control will first obtain the list of CRL URLs from the server certificate's CRL distribution points extension. The control 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 control fails with an error.

When set to 0 (default) the CRL check will not be performed by the control. 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 control 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 control 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 by default, but can be set to 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.

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 control 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 control 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 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 control 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 control fails with an error.

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 control 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 control is activated the OutBufferSize reverts to its defined size. The same happens if you attempt to make it too large or too small.

Base Config Settings

CodePage:   The system code page used for Unicode to Multibyte translations.

The default code page is Unicode UTF-8 (65001).

The following is a list of valid code page identifiers:

IdentifierName
037IBM EBCDIC - U.S./Canada
437OEM - United States
500IBM EBCDIC - International
708Arabic - ASMO 708
709Arabic - ASMO 449+, BCON V4
710Arabic - Transparent Arabic
720Arabic - Transparent ASMO
737OEM - Greek (formerly 437G)
775OEM - Baltic
850OEM - Multilingual Latin I
852OEM - Latin II
855OEM - Cyrillic (primarily Russian)
857OEM - Turkish
858OEM - Multilingual Latin I + Euro symbol
860OEM - Portuguese
861OEM - Icelandic
862OEM - Hebrew
863OEM - Canadian-French
864OEM - Arabic
865OEM - Nordic
866OEM - Russian
869OEM - Modern Greek
870IBM EBCDIC - Multilingual/ROECE (Latin-2)
874ANSI/OEM - Thai (same as 28605, ISO 8859-15)
875IBM EBCDIC - Modern Greek
932ANSI/OEM - Japanese, Shift-JIS
936ANSI/OEM - Simplified Chinese (PRC, Singapore)
949ANSI/OEM - Korean (Unified Hangul Code)
950ANSI/OEM - Traditional Chinese (Taiwan; Hong Kong SAR, PRC)
1026IBM EBCDIC - Turkish (Latin-5)
1047IBM EBCDIC - Latin 1/Open System
1140IBM EBCDIC - U.S./Canada (037 + Euro symbol)
1141IBM EBCDIC - Germany (20273 + Euro symbol)
1142IBM EBCDIC - Denmark/Norway (20277 + Euro symbol)
1143IBM EBCDIC - Finland/Sweden (20278 + Euro symbol)
1144IBM EBCDIC - Italy (20280 + Euro symbol)
1145IBM EBCDIC - Latin America/Spain (20284 + Euro symbol)
1146IBM EBCDIC - United Kingdom (20285 + Euro symbol)
1147IBM EBCDIC - France (20297 + Euro symbol)
1148IBM EBCDIC - International (500 + Euro symbol)
1149IBM EBCDIC - Icelandic (20871 + Euro symbol)
1200Unicode UCS-2 Little-Endian (BMP of ISO 10646)
1201Unicode UCS-2 Big-Endian
1250ANSI - Central European
1251ANSI - Cyrillic
1252ANSI - Latin I
1253ANSI - Greek
1254ANSI - Turkish
1255ANSI - Hebrew
1256ANSI - Arabic
1257ANSI - Baltic
1258ANSI/OEM - Vietnamese
1361Korean (Johab)
10000MAC - Roman
10001MAC - Japanese
10002MAC - Traditional Chinese (Big5)
10003MAC - Korean
10004MAC - Arabic
10005MAC - Hebrew
10006MAC - Greek I
10007MAC - Cyrillic
10008MAC - Simplified Chinese (GB 2312)
10010MAC - Romania
10017MAC - Ukraine
10021MAC - Thai
10029MAC - Latin II
10079MAC - Icelandic
10081MAC - Turkish
10082MAC - Croatia
12000Unicode UCS-4 Little-Endian
12001Unicode UCS-4 Big-Endian
20000CNS - Taiwan
20001TCA - Taiwan
20002Eten - Taiwan
20003IBM5550 - Taiwan
20004TeleText - Taiwan
20005Wang - Taiwan
20105IA5 IRV International Alphabet No. 5 (7-bit)
20106IA5 German (7-bit)
20107IA5 Swedish (7-bit)
20108IA5 Norwegian (7-bit)
20127US-ASCII (7-bit)
20261T.61
20269ISO 6937 Non-Spacing Accent
20273IBM EBCDIC - Germany
20277IBM EBCDIC - Denmark/Norway
20278IBM EBCDIC - Finland/Sweden
20280IBM EBCDIC - Italy
20284IBM EBCDIC - Latin America/Spain
20285IBM EBCDIC - United Kingdom
20290IBM EBCDIC - Japanese Katakana Extended
20297IBM EBCDIC - France
20420IBM EBCDIC - Arabic
20423IBM EBCDIC - Greek
20424IBM EBCDIC - Hebrew
20833IBM EBCDIC - Korean Extended
20838IBM EBCDIC - Thai
20866Russian - KOI8-R
20871IBM EBCDIC - Icelandic
20880IBM EBCDIC - Cyrillic (Russian)
20905IBM EBCDIC - Turkish
20924IBM EBCDIC - Latin-1/Open System (1047 + Euro symbol)
20932JIS X 0208-1990 & 0121-1990
20936Simplified Chinese (GB2312)
21025IBM EBCDIC - Cyrillic (Serbian, Bulgarian)
21027Extended Alpha Lowercase
21866Ukrainian (KOI8-U)
28591ISO 8859-1 Latin I
28592ISO 8859-2 Central Europe
28593ISO 8859-3 Latin 3
28594ISO 8859-4 Baltic
28595ISO 8859-5 Cyrillic
28596ISO 8859-6 Arabic
28597ISO 8859-7 Greek
28598ISO 8859-8 Hebrew
28599ISO 8859-9 Latin 5
28605ISO 8859-15 Latin 9
29001Europa 3
38598ISO 8859-8 Hebrew
50220ISO 2022 Japanese with no halfwidth Katakana
50221ISO 2022 Japanese with halfwidth Katakana
50222ISO 2022 Japanese JIS X 0201-1989
50225ISO 2022 Korean
50227ISO 2022 Simplified Chinese
50229ISO 2022 Traditional Chinese
50930Japanese (Katakana) Extended
50931US/Canada and Japanese
50933Korean Extended and Korean
50935Simplified Chinese Extended and Simplified Chinese
50936Simplified Chinese
50937US/Canada and Traditional Chinese
50939Japanese (Latin) Extended and Japanese
51932EUC - Japanese
51936EUC - Simplified Chinese
51949EUC - Korean
51950EUC - Traditional Chinese
52936HZ-GB2312 Simplified Chinese
54936Windows XP: GB18030 Simplified Chinese (4 Byte)
57002ISCII Devanagari
57003ISCII Bengali
57004ISCII Tamil
57005ISCII Telugu
57006ISCII Assamese
57007ISCII Oriya
57008ISCII Kannada
57009ISCII Malayalam
57010ISCII Gujarati
57011ISCII Punjabi
65000Unicode UTF-7
65001Unicode UTF-8

The following is a list of valid code page identifiers for Mac OS only:

IdentifierName
1ASCII
2NEXTSTEP
3JapaneseEUC
4UTF8
5ISOLatin1
6Symbol
7NonLossyASCII
8ShiftJIS
9ISOLatin2
10Unicode
11WindowsCP1251
12WindowsCP1252
13WindowsCP1253
14WindowsCP1254
15WindowsCP1250
21ISO2022JP
30MacOSRoman
10UTF16String
0x90000100UTF16BigEndian
0x94000100UTF16LittleEndian
0x8c000100UTF32String
0x98000100UTF32BigEndian
0x9c000100UTF32LittleEndian
65536Proprietary

UseInternalSecurityAPI:   Tells the control whether or not to use the system security libraries or an internal implementation.

By default the control will use the system security libraries to perform cryptographic functions where applicable. Setting this to tells the control to use the internal implementation instead of using the system's security API.

Trappable Errors (MQTT Control)

MQTT Errors

20501    MQTT protocol error. Refer to the error message for more information.
20502    Packet Id pool exhausted, no more packet Ids are available.
20503    Invalid topic name. Refer to the error message for more information.
20504    Invalid topic filter. Refer to the error message for more information.
20505    Message data is malformed.
20506    Invalid QoS value. Refer to the error message for more information.

WebSocket Errors

24002    Error transmitting packet.
24003    Error sending CLOSE packet.
24004    General protocol error.

HTTP Errors

20119    Firewall Error. Error description contains detailed message.
20144    Busy executing current method.
20152    HTTP protocol error. The error message has the server response.
20153    No server specified in URL
20154    Specified URLScheme is invalid.
20156    Range operation is not supported by server.
20157    Invalid cookie index (out of range).
20302    Interrupted.
20303    Can't open AttachedFile.

The control may also return one of the following error codes, which are inherited from other controls.

TCPClient Errors

20101    You cannot change the RemotePort at this time. A connection is in progress.
20102    You cannot change the RemoteHost (Server) at this time. A connection is in progress.
20103    The RemoteHost address is invalid (0.0.0.0).
20105    Already connected. If you want to reconnect, close the current connection first.
20107    You cannot change the LocalPort at this time. A connection is in progress.
20108    You cannot change the LocalHost at this time. A connection is in progress.
20113    You cannot change MaxLineLength at this time. A connection is in progress.
20117    RemotePort cannot be zero. Please specify a valid service port number.
20118    You cannot change the UseConnection option while the control is active.
20136    Operation would block.
20202    Timeout.
20212    Action impossible in control's present state.
20213    Action impossible while not connected.
20214    Action impossible while listening.
20302    Timeout.
20303    Could not open file.
20435    Unable to convert string to selected CodePage.
21106    Already connecting. If you want to reconnect, close the current connection first.
21118    You need to connect first.
21120    You cannot change the LocalHost at this time. A connection is in progress.
21121    Connection dropped by remote host.

SSL Errors

20271    Cannot load specified security library.
20272    Cannot open certificate store.
20273    Cannot find specified certificate.
20274    Cannot acquire security credentials.
20275    Cannot find certificate chain.
20276    Cannot verify certificate chain.
20277    Error during handshake.
20281    Error verifying certificate.
20282    Could not find client certificate.
20283    Could not find server certificate.
20284    Error encrypting data.
20285    Error decrypting data.

TCP/IP Errors

25005    [10004] Interrupted system call.
25010    [10009] Bad file number.
25014    [10013] Access denied.
25015    [10014] Bad address.
25023    [10022] Invalid argument.
25025    [10024] Too many open files.
25036    [10035] Operation would block.
25037    [10036] Operation now in progress.
25038    [10037] Operation already in progress.
25039    [10038] Socket operation on non-socket.
25040    [10039] Destination address required.
25041    [10040] Message too long.
25042    [10041] Protocol wrong type for socket.
25043    [10042] Bad protocol option.
25044    [10043] Protocol not supported.
25045    [10044] Socket type not supported.
25046    [10045] Operation not supported on socket.
25047    [10046] Protocol family not supported.
25048    [10047] Address family not supported by protocol family.
25049    [10048] Address already in use.
25050    [10049] Can't assign requested address.
25051    [10050] Network is down.
25052    [10051] Network is unreachable.
25053    [10052] Net dropped connection or reset.
25054    [10053] Software caused connection abort.
25055    [10054] Connection reset by peer.
25056    [10055] No buffer space available.
25057    [10056] Socket is already connected.
25058    [10057] Socket is not connected.
25059    [10058] Can't send after socket shutdown.
25060    [10059] Too many references, can't splice.
25061    [10060] Connection timed out.
25062    [10061] Connection refused.
25063    [10062] Too many levels of symbolic links.
25064    [10063] File name too long.
25065    [10064] Host is down.
25066    [10065] No route to host.
25067    [10066] Directory not empty
25068    [10067] Too many processes.
25069    [10068] Too many users.
25070    [10069] Disc Quota Exceeded.
25071    [10070] Stale NFS file handle.
25072    [10071] Too many levels of remote in path.
25092    [10091] Network subsystem is unavailable.
25093    [10092] WINSOCK DLL Version out of range.
25094    [10093] Winsock not loaded yet.
26002    [11001] Host not found.
26003    [11002] Non-authoritative 'Host not found' (try again or check DNS setup).
26004    [11003] Non-recoverable errors: FORMERR, REFUSED, NOTIMP.
26005    [11004] Valid name, no data record (check DNS setup).

Copyright (c) 2022 /n software inc. - All rights reserved.
IPWorks IoT 2022 ActiveX Edition - Version 22.0 [Build 8369]