DatagramChannel time server, Provide RFC 868 time service (http://www.ietf.org/rfc/rfc0868.txt) - Java Network

Java examples for Network:Datagram Channel

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Description

DatagramChannel time server, Provide RFC 868 time service (http://www.ietf.org/rfc/rfc0868.txt)

Demo Code

import java.net.InetSocketAddress;
import java.net.SocketAddress;
import java.net.SocketException;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.channels.DatagramChannel;

public class Main {
  private static final int DEFAULT_TIME_PORT = 9999;
  private static final long DIFF_1900 = 2208988800L;

  protected DatagramChannel channel;

  public Main() throws Exception {
    this.channel = DatagramChannel.open();
    this.channel.socket().bind(new InetSocketAddress(DEFAULT_TIME_PORT));
    System.out.println("Listening on port " + DEFAULT_TIME_PORT+ " for time requests");
  }// w  ww.j  a  v a2s. com
  public void listen() throws Exception {
    ByteBuffer longBuffer = ByteBuffer.allocate(8);
    longBuffer.order(ByteOrder.BIG_ENDIAN);
    longBuffer.putLong(0, 0);
    longBuffer.position(4);
    ByteBuffer buffer = longBuffer.slice();
    while (true) {
      buffer.clear();
      SocketAddress sa = this.channel.receive(buffer);
      if (sa == null) {
        continue;
      }
      System.out.println("Time request from " + sa);
      buffer.clear();
      longBuffer.putLong(0, (System.currentTimeMillis() / 1000) + DIFF_1900);

      this.channel.send(buffer, sa);
    }
  }
  public static void main(String[] argv) throws Exception {
    try {
      Main server = new Main();
      server.listen();
    } catch (SocketException e) {
      e.printStackTrace();

    }
  }
}

Result


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