Java tutorial
import java.io.IOException; import java.net.DatagramPacket; import java.net.DatagramSocket; import java.net.InetAddress; import java.util.Date; public class Main { final private static int DAYTIME_PORT = 13; public static void main(String args[]) throws IOException { DatagramSocket socket = new DatagramSocket(DAYTIME_PORT); while (true) { byte buffer[] = new byte[256]; DatagramPacket packet = new DatagramPacket(buffer, buffer.length); socket.receive(packet); String date = new Date().toString(); buffer = date.getBytes(); // Get response address/port for client from packet InetAddress address = packet.getAddress(); int port = packet.getPort(); packet = new DatagramPacket(buffer, buffer.length, address, port); socket.send(packet); } } }