import java.net.*;
import java.io.*;
public class UDPServer{
	public static void main(String args[]){
	    try{
	    	DatagramSocket aSocket = new DatagramSocket(6789);
		byte[] buffer = new byte[1000];
 		while(true){
 		    DatagramPacket request = new DatagramPacket(buffer, buffer.length);
  		   aSocket.receive(request);
    		   DatagramPacket reply = new DatagramPacket(request.getData(),
		   	request.getLength(), request.getAddress(), request.getPort());
		   aSocket.send(reply);
		}
	    }catch (SocketException e){System.out.println("Socket: " + e.getMessage());
	   }catch (IOException e) {System.out.println("IO: " + e.getMessage());}
    }
}