public void run() throws MqttException {
    // register MQTT and connect
    publisher = new Messenger(CLIENT_ID + "Pub", publisherCallBack());
    subscriber = new Messenger(CLIENT_ID, subscriberCallBack());
    subscriber.connect();

    // subscribe to all required topics
    try {
      subscriber.subscribe("RouteList");
      subscriber.subscribe("Monitor/#");
      // messenger.subscribe("Call/Floor/#");
      // messenger.subscribe("Call/Hall/#");
    } catch (MqttException e) {
      e.printStackTrace();
    }
  }