Using Datagrams to Get the Date

[Java Tip]

This Java tip shows how to get the current date using datagrams.

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

public class GetDate {
  final static int PortDayTime = 13; // well-known daytime port

  public static void main(String args[]) throws Exception {
    byte msg[] = new byte[256];
    DatagramSocket dgSocket = new DatagramSocket();
    InetAddress destination = InetAddress.getByName("web.mit.edu");
    DatagramPacket datagram = new DatagramPacket(msg, msg.length,
        destination, PortDayTime);
    dgSocket.send(datagram);
    datagram = new DatagramPacket(msg, msg.length);
    dgSocket.receive(datagram);
    String received = new String(datagram.getData());
    System.out.println("The time in Cambridge is now: " + received);
    dgSocket.close();
  }
}