MQTTPublish (Function)

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MQTTPublish (Function)

In french: MQTTPublie

Publishes a message on the MQTT broker.

Versions 24 and later

This function is now available for Android applications.

New in version 24

This function is now available for Android applications.

Example

gMqttSession is mqttSession
llResult is int
sTopic is string
bufContent is Buffer

gMqttSession..Address = "xxx.xx.xxx.xxx" // To fill
gMqttSession..Port = 1883
gMqttSession..ClientID = "MyTest"
gMqttSession..CleanSession = True

sTopic = "/SERVER"
bufContenu = "Test from WINDEV"

IF NOT MQTTConnect(gMqttSession) THEN
Error("Connection problem. '" + ErrorInfo() + "')")
END

llResult = MQTTPublish(gMqttSession, sTopic, bufContent)

llResult is int
sTopic = "/SERVER"
bufContenu = "Test from WINDEV"
llResult = MQTTPublish(gMqttSession, sTopic, bufContent, True, ...
mqttQualityExactlyOnce, PublicationMQTT)

INTERNAL PROCEDURE PublicationMQTT(pMqttSession is mqttSession, MessageNum is int)
Trace("Publication" + " - MessageNum = " + MessageNum)
END

Syntax

<Result> = MQTTPublish(<MQTT session> , <Topic> , <Data> [, <To store> [, <Quality of service> [, <Procedure>]]])

<Result>: Integer

Number of published message (mqttQualityExactlyOnce and mqttQualityAtLeastOnce constants).
0 if the publication is successful (mqttQualityAtMostOnce constant).
-1 if an error occurred.

<MQTT session>: mqttSession variable

Name of mqttSession variable corresponding to the MQTT session to use.

<Topic>: Character string (with quotes)

Message topic.

<Data>: Buffer

Data to publish (must not exceed 256MB).

<To store>: Optional boolean

True if the message must be stored on the server.
False (by default) otherwise.

<Quality of service>: Optional integer

Requested service quality:
mqttQualityAtMostOnce The message will be delivered once at most. The message is not stored. It is sent without guarantee of receipt. The MQTT (broker) does not inform the sender that the message was received. The message can be lost if the client is disconnected or if the server is stopped.
Equivalent to QOS set to 0.
mqttQualityExactlyOnce The message will be necessarily saved by the issuer. It will be transmitted as long as the receiver does not confirm its sending on the network. The issuer is using a sophisticated recognition with the server (broker) to avoid duplicating messages. This mode is slower but it is more secure.
Equivalent to QOS set to 2.
mqttQualityAtLeastOnce The message will be delivered at least once. The client will transmit the message several times if necessary until the server (broker) confirms that the message was transmitted on the network.
Equivalent to QOS set to 1.

<Procedure>: Name of optional WLanguage procedure

Name of WLanguage procedure ("callback") run when the message was published (this procedure is called if the mqttQualityExactlyOnce and mqttQualityAtLeastOnce constants are used). This procedure has the following format:

PROCEDURE <Procedure name>(<Session> is mqttSession,
<Message num> is int)

where:
<Session> corresponds to a mqttSession variable containing the characteristics of MQTT session.
<Message num> corresponds to the number of published message.

Component : wd240com.dll