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Using the MQTT transport

Example use case

This sample demonstrates how to run a Pub-Sub use case using MQTT as the broker. the MQTT listener in the Micro Integrator consumes messages from a MQTT topic, and the MQTT sender publishes messages to a MQTT topic.

Synapse configuration

<proxy xmlns="http://ws.apache.org/ns/synapse" name="SampleProxy" transports="mqtt" startOnLoad="true" trace="disable">
    <description/>
    <target>
        <endpoint>
            <address uri="mqtt:/SampleProxy?mqtt.server.host.name=localhost&amp;mqtt.server.port=1883&amp;mqtt.client.id=esb.test.sender&amp;mqtt.topic.name=esb.test2&amp;mqtt.subscription.qos=2&amp;mqtt.blocking.sender=true"/>
        </endpoint>
        <inSequence>
            <property name="OUT_ONLY" value="true"/>
            <property name="FORCE_SC_ACCEPTED" value="true" scope="axis2" type="STRING"/>
        </inSequence>
        <outSequence>
            <send/>
        </outSequence>
    </target>
    <parameter name="mqtt.connection.factory">mqttConFactory</parameter>
    <parameter name="mqtt.topic.name">esb.test1</parameter>
    <parameter name="mqtt.subscription.qos">2</parameter>
    <parameter name="mqtt.content.type">text/plain</parameter>
    <parameter name="mqtt.session.clean">false</parameter>
</proxy>  

Add the following configurations to enable the MQTT listener and sender in <MI_HOME>/conf/deployment.toml file.

[transport.mqtt]
listener.enable = true
listener.hostname = "localhost"
listener.connection_factory = "mqttConFactory"
listener.server_port = 1883
listener.client_id = "client-id-1234"
listener.topic_name = "esb.test2"

sender.enable = true

Build and run

  • Download the org.eclipse.paho.client.mqttv3-1.1.0.jar file.
  • Download mosquitto MQTT broker (http://mosquitto.org/)
  • Copy the org.eclipse.paho.client.mqttv3-1.1.0.jar file to the MI_HOME/lib/ directory.
  • Start the MQTT broker.

Invoke the proxy service:

  • Execute the following command to start the MQTT subscriber on the esb.test2 topic:

    mosquitto_sub -h localhost -t esb.test2
  • Execute the following command to run the MQTT publisher to publish to the esb.test1 topic:

    mosquitto_pub -h localhost -p 1883 -t esb.test1  -m {"company":"WSO2"}

When you analyze the output messages on the MQTT subscriber console, you will see the following log:

{"company":"WSO2"}
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