UDP time server based on New IO : UDP Server « Network « Java Tutorial

1. Java Tutorial
2. Network
3. UDP Server

import java.io.IOException;
import java.net.DatagramSocket;
import java.net.InetSocketAddress;
import java.net.SocketAddress;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.channels.DatagramChannel;

public class UDPTimeServer {

  public final static int DEFAULT_PORT = 37;

  public static void main(String[] args) throws IOException {

    int port = 37;

    ByteBuffer in = ByteBuffer.allocate(8192);
    ByteBuffer out = ByteBuffer.allocate(8);
    out.order(ByteOrder.BIG_ENDIAN);
    SocketAddress address = new InetSocketAddress(port);
    DatagramChannel channel = DatagramChannel.open();
    DatagramSocket socket = channel.socket();
    socket.bind(address);
    System.err.println("bound to " + address);
    while (true) {
      try {
        in.clear();
        SocketAddress client = channel.receive(in);
        System.err.println(client);
        long secondsSince1970 = System.currentTimeMillis();
        out.clear();
        out.putLong(secondsSince1970);
        out.flip();

        out.position(4);
        channel.send(out, client);
      } catch (Exception ex) {
        System.err.println(ex);
      }
    }
  }
}