import java.net.*;
import java.io.*;

public class MyGroupAPI
{
	int port;
	InetAddress inet;
	MulticastSocket socket;

	public MyGroupAPI(int port) throws Exception
	{
		this.port = port;
		socket = new MulticastSocket(port);

	}

	public void joinGroup(String address) throws Exception
	{
		inet = InetAddress.getByName(address);
		socket.joinGroup(inet);

	}

	public void sendMessage(String message) throws Exception
	{
		DatagramPacket dp = new DatagramPacket(message.getBytes(),message.length(),inet.port);
		socket.send(dp);
	}

	public String receiveMessage() throws Exception
	{
		byte [] buff = new byte[1000];
		DatagramPacket dp = new DatagramPacket(buff,buff.length);
		socket.receive(dp);
		String msg = new String(buff);
		return dp.getSocketAddress()+":"+msg.trim();
	}

	public static void main(String [] args) throws Exception
	{
		try{
			for(;;){
				MyGroupAPI ap = new MyGroupAPI(2020);
				ap.joinGroup("255.5.5.5");
				BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
				System.out.print("Message: ");
				String msg = br.readLine();
				ap.sendMessage(msg);
				System.out.println("Message received: ");
				System.out.println(ap.receiveMessage());
			}
		    }
		    catch(Exception e)
		    {
		    }
	}
}