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

public class UdpServer {
  private static final java.text.DateFormat DF = java.text.DateFormat.getDateTimeInstance();
  private static String getTime() {
    return DF.format(new java.util.Date());
  }
  public static void main(String[] args) {
  	try {
      DatagramSocket ds = new DatagramSocket(4711);
      DatagramPacket dp = new DatagramPacket(new byte[20], 20);
      while (true) {
        ds.receive(dp);
        System.out.println("Anforderung von Port " + dp.getPort());
        dp.setData(getTime().getBytes());
        ds.send(dp);
      }
    } catch (SocketException e) { e.printStackTrace();}
	  catch (IOException e) { e.printStackTrace();}
  }
}