import java.net.*;
import java.io.*;
class UDPServer{
    public static void main(String args[]){ 
	DatagramSocket aSocket = null;
	try{
	    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());
		System.out.println("Server:" + new String (request.getData()));
		aSocket.send(reply);
	    }
	}
	catch (SocketException e){System.out.println("Socket: " + e.getMessage());}
	catch (IOException e) {System.out.println("IO: " + e.getMessage());}
        finally {if(aSocket != null) aSocket.close();}
}
}