Time-service client using DatagramChannel - Java Network

Java examples for Network:Datagram Channel

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Description

Time-service client using DatagramChannel

Demo Code

import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.channels.DatagramChannel;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;

public class Main {
  protected int port = 9999;
  protected List remoteHosts;
  protected DatagramChannel channel;

  public Main() throws Exception {
    this.channel = DatagramChannel.open();
  }//w ww  .  j  a va  2 s  . c om
  protected InetSocketAddress receivePacket(DatagramChannel channel,
      ByteBuffer buffer) throws Exception {
    buffer.clear();
    return ((InetSocketAddress) channel.receive(buffer));
  }
  protected void sendRequests() throws Exception {
    ByteBuffer buffer = ByteBuffer.allocate(1);
    Iterator it = remoteHosts.iterator();
    while (it.hasNext()) {
      InetSocketAddress sa = (InetSocketAddress) it.next();
      buffer.clear().flip();
      channel.send(buffer, sa);
    }
  }
  public void getReplies() throws Exception {
    ByteBuffer longBuffer = ByteBuffer.allocate(8);
    longBuffer.order(ByteOrder.BIG_ENDIAN);
    longBuffer.putLong(0, 0);
    longBuffer.position(4);

    ByteBuffer buffer = longBuffer.slice();
    int expect = remoteHosts.size();
    int replies = 0;

    System.out.println("Waiting for replies...");
    while (true) {
      InetSocketAddress sa;
      sa = receivePacket(channel, buffer);
      buffer.flip();
      replies++;
      printTime(longBuffer.getLong(0), sa);
      if (replies == expect) {
        System.out.println("All packets answered");
        break;
      }
      System.out.println("Received " + replies + " of " + expect + " replies");
    }
  }
  protected void printTime(long remote1900, InetSocketAddress sa) {
    System.out.println("Reply from " + sa.getHostName() + ":" + sa.getPort());
  }

  protected void parseArgs(String[] argv) {
    remoteHosts = new LinkedList();
    InetSocketAddress sa = new InetSocketAddress("127.0.0.1", port);
    remoteHosts.add(sa);
  }
  public static void main(String[] argv) throws Exception {
    Main client = new Main();

    client.sendRequests();
    client.getReplies();
  }
}

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