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Stored procedures
Used to subscribe to a MQTT notification.
Remark: This subscription can be stopped by MQTTUnsubscribe and MQTTUnsubscribeAll.
Example
gMqttSession is mqttSession
...
lbRésultat is boolean
lbRésultat = MQTTSubscribe(gMqttSession, "sensors/sensor1/temprature1", mqttQualityAtLeastOnce, ...
Proc_MQTTAbonne)
 
// La procédure spécifiée dans la fonction MQTTAbonne doit être une procédure globale du projet
PROCÉDURE Proc_MQTTAbonne(pMqttSession is mqttSession, ...
Topic is string, unbuffer is Buffer)
Trace("Abonnement")
END
Syntax
<Result> = MQTTSubscribe(<MQTT session> , <Topic> , <Quality> , <Procedure>)
<Result>: Boolean
  • True if the subscription is implemented,
  • False otherwise.
<MQTT session>: mqttSession variable
Name of the mqttSession variable corresponding to the MQTT session to be used.
<Topic>: Character string
Topic for which the subscription is requested.
<Quality>: Integer constant
Requested quality:
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.
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 is using a sophisticated recognition with the server (broker) to avoid duplicating messages. This mode is slower but it is more secure.
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.
<Procedure>: Name of WLanguage procedure
Name of the WLanguage procedure (also called "callback") executed at each new Notification.
This must be an Procedure that is comprehensive of theproject : using an internal procedure is not allowed. This procedure has the following format:
PROCEDURE <Nom de la procédure>(<Connexion> est un mqttSession,
<Sujet> est une chaîne, <Message> est un Buffer)
where:
  • <Connection> corresponds to a mqttSession variable containing the characteristics of MQTT session.
  • <Topic> corresponds to the message topic.
  • <Message> corresponds to the message content.
Business / UI classification: Business Logic
Component: wd270com.dll
Minimum version required
  • Version 22
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