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Help / WLanguage / WLanguage functions / Communication / MQTT functions
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Stored procedures
Publishes a message on the MQTT broker.
Example
gMqttSession is mqttSession
llRésultat is int
sSujet is string
bufContenu is Buffer

gMqttSession.Address = "xxx.xx.xxx.xxx" // A remplir
gMqttSession.Port = 1883
gMqttSession.ClientID = "MonTest"
gMqttSession.CleanSession = True

sSujet = "/SERVER"
bufContenu = "Test à partir de WINDEV"

IF NOT MQTTConnect(gMqttSession) THEN
	Error("Problème de connexion. '" + ErrorInfo() + "')")
END

llRésultat = MQTTPublish(gMqttSession, sSujet, bufContenu)
llRésultat is int
sSujet = "/SERVER"
bufContenu = "Test à partir de WINDEV"
llRésultat = MQTTPublish(gMqttSession, sSujet, bufContenu, True, ...
	mqttQualityExactlyOnce,  PublicationMQTT)

INTERNAL PROCEDURE PublicationMQTT(pMqttSession is mqttSession, NumMessage is int)
Trace("Publication" + " - NumMessage = " + NumMessage)
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 the mqttSession variable corresponding to the MQTT session to be used.
<Topic>: Character string
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:
mqttQualityAtLeastOnceThe 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.
mqttQualityAtMostOnceThe 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.
mqttQualityExactlyOnceThe 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 uses 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.
<Procedure>: Optional procedure name
Name of the WLanguage procedure (also called "callback") executed when the message has been broadcast (this procedure is called if the constants mqttQualityExactlyOnce constants and mqttQualityAtLeastOnce constants 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.
Business / UI classification: Business Logic
Component: wd300com.dll
Minimum version required
  • Version 22
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Last update: 03/28/2025

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