The Eclipse Paho project provides open-source client implementations of the MQTT and MQTT-SN messaging protocols aimed at new, existing, and emerging applications for the Internet of Things.

To get started, download the Paho library for Android from the following GitHub project.

Integration Steps

Step 1: Initialize a client, set required options, and connect:

MqttAndroidClient mqttClient = new MqttAndroidClient(BaseApplication.getAppContext(), broker, MQTT_CLIENT_ID);
//Set call back class
mqttClient.setCallback(new MqttCallbackHandler(BaseApplication.getAppContext()));
MqttConnectOptions connOpts = new MqttConnectOptions();
IMqttToken token = mqttClient.connect(connOpts);

Step 2: Subscribe to a topic:

token.setActionCallback(new IMqttActionListener() {
      @Override
      public void onSuccess(IMqttToken arg0) {
           mqttClient.subscribe("TOPIC_NAME" + userId, 2, null, new IMqttActionListener() {
                @Override
                public void onSuccess(IMqttToken asyncActionToken) {
                    Log.d(LOG_TAG, "Successfully subscribed to topic.");
                }

                @Override
                public void onFailure(IMqttToken asyncActionToken, Throwable exception) {
                    Log.d(LOG_TAG, "Failed to subscribed to topic.");
                }
            });
      }

      @Override
      public void onFailure(IMqttToken arg0, Throwable arg1) {
           Log.d(LOG_TAG, errorMsg);
      }
    });

Step 3: Define the callback handler class:

public class MqttCallbackHandler implements MqttCallbackExtended {
        @Override
            public void connectComplete(boolean b, String s) {
                Log.w("mqtt", s);
            }

            @Override
            public void connectionLost(Throwable throwable) {

            }

            @Override
            public void messageArrived(String topic, MqttMessage mqttMessage) throws Exception {
                Log.w("Anjing", mqttMessage.toString());
            }

            @Override
            public void deliveryComplete(IMqttDeliveryToken iMqttDeliveryToken) {

            }
      }

Step 4: Add the entry in the manifest file:

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

The new library makes it so much easier to integrate and also includes an auto-reconnect feature, so if an application goes in and out of the network, it auto-reconnects to the server.