DEPRAG Smart Documentation

TwinCAT TIA

Network MQTT Client ActiveClients One client

ns=2;s=DEPRAG Smart/Network/MQTT/ActiveClients/0/Subscribe

Subscribes to an MQTT topic with default settings from the MQTT broker.

Parameters:

Topic
The topic to subscribe to.

Returns:

Subscribe
A variable of type OpcMethodReturnValueVoid.

In addition to the parameters already explained, the following variables must be created / transferred for the implementation in TwinCAT 3:

Beckhoff parameter:

bMqttSubscribe
A boolean variable that can be used to trigger the execution of the Subscribe command.

OutputDataMqttSubscribe
An instance of the ST_VoidOutputData structure into which the return value of the Subscribe method is written.

hrMqttSubscribe
This can be used to monitor the execution of the command. Error codes have the type HRESULT.

fbMqtt
An instance of the "FB_Mqtt" function block supplied with the DEPRAG Smart library.

sTopic
A string(255) variable that specifies the topic to subscribe to.

sClientId
A String(255) variable that specifies the client that should execute the command.

ConnectionHandle
"ConnectionHandle" received when establishing a connection between DEPRAG Smart Server and your OPC UA client.



VAR
   bMqttSubscribe          : BOOL;
   OutputDataMqttSubscribe        : ST_VoidOutputData;
   hrMqttSubscribe          : HRESULT;

   fbMqtt  : FB_Mqtt;
END_VAR

hrMqttSubscribe := fbMqtt.Subscribe(
     bExecute   := bMqttSubscribe, 
     ConnectionHandle := depragSmartConnection.ConnectionHandle, 
     sTopic    := 'testSmart/test', 
     sClientId   := '0', 
     OutputData   => OutputDataMqttSubscribe);
IF hrMqttSubscribe <> S_FALSE THEN 
    bMqttSubscribe := FALSE;
END_IF

For examples and explanations regarding the calls of nodes via Siemens TIA Portal please refer to the sub-menu "Siemens TIA Portal" in section "Getting Started".