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

public class Srv {
	public static void main(String args[]) {
		DatagramSocket dsock;
		DatagramPacket dpack;
		int p;
		byte b[]=new byte[20];
		try {
			dsock=new DatagramSocket(4200);		
			dpack=new DatagramPacket(new byte[20],20);
			dsock.receive(dpack);
			p=dpack.getPort();
			System.out.println("received packet from "+dpack.getAddress().getHostName()+" dport: "+dpack.getPort());
			System.out.println(new String(dpack.getData()));
			dpack=new DatagramPacket("hello client".getBytes(),"hello client".length(),dpack.getAddress(),p);//InetAddress.getByName("nessie.cs.ubbcluj.ro");			
			dsock.send(dpack);
		} catch (Exception ex) {System.out.println(ex.getMessage());}
	}
}