MQTTClient.java

private void connect() {
        MqttConnectOptions connectOptions = new MqttConnectOptions();
        connectOptions.setAutomaticReconnect(true);

        client = new MqttAndroidClient(this, serverURI, clientId);
        try {
            client.connect(connectOptions, new IMqttActionListener() {
                @Override
                public void onSuccess(IMqttToken asyncActionToken) {
                    subscribe();
                }

                @Override
                public void onFailure(IMqttToken asyncActionToken, Throwable e) {
                    e.printStackTrace();
                }
            });
        } catch (MqttException e) {
            e.printStackTrace();
        }
    }