Publish a Message From Android on MQTT

AndroidManifest.xml

    <!-- Permissions the Application Requires -->
    <uses-permission android:name="android.permission.WAKE_LOCK" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

    <!--<uses-permission android:name="android.permission.READ_PHONE_STATE" />-->
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.INTERNET" />

And register our MQTT Android Service in our app before the closing tag by adding this line:

 <service android:name="org.eclipse.paho.android.service.MqttService" />

Java

public class MqttManager {

    MqttAndroidClient mqtt=null;

    public void publishTest() throws MqttException {

        try
        {
            String clientId= MqttClient.generateClientId();
            mqtt=new MqttAndroidClient(CachePupli.context,"tcp://192.168.1.2:1883",clientId);
            MqttConnectOptions connectOptions=new MqttConnectOptions();
            connectOptions.setAutomaticReconnect(true);
            connectOptions.setCleanSession(true);
            IMqttToken token= mqtt.connect(connectOptions);
            token.setActionCallback(onConnect);
        }
        catch (Exception ex)
        {
            ex.printStackTrace();
        }
    }


    private IMqttActionListener onConnect=new IMqttActionListener() {
        @Override
        public void onSuccess(IMqttToken asyncActionToken) {

            MqttMessage message=new MqttMessage("Hello World".getBytes());
            try {
                mqtt.publish("test",message);
            } catch (MqttException e) {
                e.printStackTrace();
            }
        }

        @Override
        public void onFailure(IMqttToken asyncActionToken, Throwable exception) {

        }
    };
}

References
https://www.eclipse.org/paho/clients/android/
https://wildanmsyah.wordpress.com/2017/05/11/mqtt-android-client-tutorial/

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