Publish via output

Output binding

• Add the MqttAttribute to one of your functions parameters
• Use one of the constructor overloads to configure
  • The first/simple constructor which does not require any parameter
  • The second (more advanced) constructor requires a Type which you then have to implement more on this
• Make sure the type of the parameter is IMqttMessage and marked as out

Example

This is an example of an Azure Function running based on a timer trigger publishing messages to a MQTT topic:

[FunctionName("SimpleFunction")]
public static void SimpleFunction(
    [TimerTrigger("0 */5 * * * *")]TimerInfo timer,
    [Mqtt] out IMqttMessage outMessage)
{
    outMessage = new MqttMessage("testtopic/out", new byte[] { }, MqttQualityOfServiceLevel.AtLeastOnce, true);
}

It is also possible to output multiple messages in a single functions run using the ICollector output:

[FunctionName("TimerFunction")]
public static void TimerFunction( 
    [TimerTrigger("0 * * * * *")]TimerInfo timerInfo,
    [Mqtt] ICollector<IMqttMessage> outMessages)
{
    outMessages.Add(new MqttMessage("topic/one", body, MqttQualityOfServiceLevel.AtLeastOnce, true));
    outMessages.Add(new MqttMessage("topic/two", body, MqttQualityOfServiceLevel.AtLeastOnce, true));
}

Connection

The connection to the MQTT broker is made when the first message is published and then reused/kept open for later messages.