ping.java

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/*
 * Java Network Programming, Second Edition
 * Merlin Hughes, Michael Shoffner, Derek Hamner
 * Manning Publications Company; ISBN 188477749X
 *
 * http://nitric.com/jnp/
 *
 * Copyright (c) 1997-1999 Merlin Hughes, Michael Shoffner, Derek Hamner;
 * all rights reserved; see license.txt for details.
 */

import java.io.*;
import java.net.*;

public class Ping {
  static final int DEFAULT_PORT = 7;
  static final int UDP_HEADER = 20 + 8;
  static final int BACKSPACE = 8;
  
  public static void main (String[] args) throws IOException {
    parseArgs (args);
    init ();
    for (int i = 0; (i < count) || (count == 0); ++ i) {
      long past = System.currentTimeMillis ();
      ping (i, past);
      try {
        pong (i, past);
      } catch (InterruptedIOException ignored) {
      }
    }
    socket.close ();
    printStats ();
  }

  static String host = null;
  static int port, count = 32, delay = 1000, size = 64;
  static boolean flood = false;
  
  static void parseArgs (String args[]) {
    for (int i = 0; i < args.length; ++ i) {
      if (args[i].startsWith ("-")) {
        if (args[i].equals ("-c") && (i < args.length - 1))
          count = Integer.parseInt (args[++ i]);
        else if (args[i].equals ("-i") && (i < args.length - 1))
          delay = Math.max (10, Integer.parseInt (args[++ i]));
        else if (args[i].equals ("-s") && (i < args.length - 1))
          size = Integer.parseInt (args[++ i]);
        else if (args[i].equals ("-f"))
          flood = true;
        else
          syntaxError ();
      } else {
        if (host != null)
          syntaxError ();
        int colon = args[i].indexOf (":");
        host = (colon > -1) ? args[i].substring (0, colon) : args[i];
        port = ((colon > -1) && (colon < args[i].length () - 1)) ?
          Integer.parseInt (args[i].substring (colon + 1)) : DEFAULT_PORT;
      }
    }
    if (host == null)
      syntaxError ();
  }

  static void syntaxError () {
    throw new IllegalArgumentException
      ("Ping [-c count] [-i wait] [-s packetsize] [-f] <hostname>[:<port>]");
  }

  static DatagramSocket socket;
  static byte[] outBuffer, inBuffer;
  static DatagramPacket outPacket, inPacket;
  
  static void init () throws IOException {
    socket = new DatagramSocket ();
    outBuffer = new byte[Math.max (12, size - UDP_HEADER)];
    outPacket = new DatagramPacket (outBuffer, outBuffer.length,
                                    InetAddress.getByName (host), port);
    inBuffer = new byte[outBuffer.length];
    inPacket = new DatagramPacket (inBuffer, inBuffer.length);
  }

  static int sent = 0;
  
  static void ping (int seq, long past) throws IOException {
    writeInt (seq, outBuffer, 0);
    writeLong (past, outBuffer, 4);
    socket.send (outPacket);
    ++ sent;
    if (flood) {
      System.out.write ('.');
      System.out.flush ();
    }
  }

  static final void writeInt (int datum, byte[] dst, int offset) {
    dst[offset] = (byte) (datum >> 24);
    dst[offset + 1] = (byte) (datum >> 16);
    dst[offset + 2] = (byte) (datum >> 8);
    dst[offset + 3] = (byte) datum;
  }

  static final void writeLong (long datum, byte[] dst, int offset) {
    writeInt ((int) (datum >> 32), dst, offset);
    writeInt ((int) datum, dst, offset + 4);
  }

  static int received = 0;
  
  static void pong (int seq, long past) throws IOException {
    long present = System.currentTimeMillis ();
    int tmpRTT = (maxRTT == 0) ? 500 : (int) maxRTT * 2;
    int wait = Math.max (delay, (seq == count - 1) ? tmpRTT : 0);
    do {
      socket.setSoTimeout (Math.max (1, wait - (int) (present - past)));
      socket.receive (inPacket);
      ++ received;
      present = System.currentTimeMillis ();
      processPong (present);
    } while ((present - past < wait) && !flood);
  }

  static long minRTT = 100000, maxRTT = 0, totRTT = 0;
  
  static void processPong (long present) {
    int seq = readInt (inBuffer, 0);
    long when = readLong (inBuffer, 4);
    long rtt = present - when;
    if (!flood) {
      System.out.println
        ((inPacket.getLength () + UDP_HEADER) +
         " bytes from " + inPacket.getAddress ().getHostName () +
         ": seq no " + seq + " time=" + rtt + " ms");
    } else {
      System.out.write (BACKSPACE);
      System.out.flush ();
    }
    if (rtt < minRTT) minRTT = rtt;
    if (rtt > maxRTT) maxRTT = rtt;
    totRTT += rtt;
  }

  static final int readInt (byte[] src, int offset) {
    return (src[offset] << 24) | ((src[offset + 1] & 0xff) << 16) |
      ((src[offset + 2] & 0xff) << 8) | (src[offset + 3] & 0xff);
  }

  static final long readLong (byte[] src, int offset) {
    return ((long) readInt (src, offset) << 32) |
      ((long) readInt (src, offset + 4) & 0xffffffffL);
  }

  static void printStats () {
    System.out.println
      (sent + " packets transmitted, " + received + " packets received, " +
       (100 * (sent - received) / sent) + "% packet loss");
    if (received > 0)
      System.out.println ("round-trip min/avg/max = " + minRTT + '/' +
                          ((float) totRTT / received) + '/' + maxRTT + " ms");
  }
}