public static void main(String[] args) throws InterruptedException {
	Ros ros = new Ros("localhost");
	ros.connect();

	Topic echo = new Topic(ros, "/echo", "std_msgs/String");
	Message toSend = new Message("{\"data\": \"hello, world!\"}");
	echo.publish(toSend);

	Topic echoBack = new Topic(ros, "/echo_back", "std_msgs/String");
	echoBack.subscribe(new TopicCallback() {
		@Override
		public void handleMessage(Message message) {
			System.out.println("From ROS: " + message.toString());
		}
	});

	Service addTwoInts = new Service(ros, "/add_two_ints", "rospy_tutorials/AddTwoInts");

	ServiceRequest request = new ServiceRequest("{\"a\": 10, \"b\": 20}");
	ServiceResponse response = addTwoInts.callServiceAndWait(request);
	System.out.println(response.toString());
	
	ros.disconnect();
}