src/java/com/oroinc/net/CharGenUDPClient.java

/***
 * $Id: CharGenUDPClient.java,v 1.1 2002/04/03 01:04:25 brekke Exp $
 *
 * NetComponents Internet Protocol Library
 * Copyright (C) 1997-2002  Daniel F. Savarese
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library in the LICENSE file; if not, write
 * to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 * Boston, MA  02111-1307  USA
 ***/

package com.oroinc.net;

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

/***
 * The CharGenUDPClient class is a UDP implementation of a client for the
 * character generator protocol described in RFC 864.  It can also be
 * used for Systat (RFC 866), Quote of the Day (RFC 865), and netstat
 * (port 15).  All of these protocols involve sending a datagram to the
 * appropriate port, and reading data contained in one or more reply
 * datagrams.  The chargen and quote of the day protocols only send
 * one reply datagram containing 512 bytes or less of data.  The other
 * protocols may reply with more than one datagram, in which case you
 * must wait for a timeout to determine that all reply datagrams have
 * been sent.
 * <p>
 * To use the CharGenUDPClient class, just open a local UDP port
 * with <a href="com.oroinc.net.DatagramSocketClient.html#open"> open </a>
 * and call <a href="#send"> send </a> to send the datagram that will
 * initiate the data reply.  For chargen or quote of the day, just
 * call <a href="#recieve"> receive </a>, and you're done.  For netstat and
 * systat, call receive in a while loop, and catch a SocketException and
 * InterruptedIOException to detect a timeout (don't forget to set the
 * timeout duration beforehand).  Don't forget to call
 * <a href="com.oroinc.net.DatagramSocketClient.html#close"> close() </a>
 * to clean up properly.
 * <p>
 * <p>
 * @author Daniel F. Savarese
 * @see CharGenTCPClient
 ***/

public final class CharGenUDPClient extends DatagramSocketClient {
  /*** The systat port value of 11 according to RFC 866. ***/
  public static final int SYSTAT_PORT       = 11;
  /*** The netstat port value of 19. ***/
  public static final int NETSTAT_PORT      = 15;
  /*** The quote of the day port value of 17 according to RFC 865. ***/
  public static final int QUOTE_OF_DAY_PORT = 17;
  /*** The character generator port value of 19 according to RFC 864. ***/
  public static final int CHARGEN_PORT      = 19;
  /*** The default chargen port.  It is set to 19 according to RFC 864. ***/
  public static final int DEFAULT_PORT      = 19;

  private byte[] __receiveData;
  private DatagramPacket __receivePacket;
  private DatagramPacket __sendPacket;

  /***
   * The default CharGenUDPClient constructor.  It initializes some internal
   * data structures for sending and receiving the necessary datagrams for
   * the chargen and related protocols.
   ***/
  public CharGenUDPClient() {
    // CharGen return packets have a maximum length of 512
    __receiveData   = new byte[512];
    __receivePacket = new DatagramPacket(__receiveData, 512);
    __sendPacket    = new DatagramPacket(new byte[0], 0);
  }


  /***
   * Sends the data initiation datagram.  This data in the packet is ignored
   * by the server, and merely serves to signal that the server should send
   * its reply.
   * <p>
   * @param host The address of the server.
   * @param port The port of the service.
   * @exception IOException If an error occurs while sending the datagram.
   ***/
  public void send(InetAddress host, int port) throws IOException {
    __sendPacket.setAddress(host);
    __sendPacket.setPort(port);
    _socket_.send(__sendPacket);
  }

  /*** Same as <code>send(host, CharGenUDPClient.DEFAULT_PORT);</code> ***/
  public void send(InetAddress host)  throws IOException {
    send(host, DEFAULT_PORT);
  }

  /***
   * Receive the reply data from the server.  This will always be 512 bytes
   * or less.  Chargen and quote of the day only return one packet.  Netstat
   * and systat require multiple calls to receive() with timeout detection.
   * <p>
   * @return The reply data from the server.
   * @exception IOException If an error occurs while receiving the datagram.
   ***/
  public byte[] receive() throws IOException {
    int length;
    byte[] result;

    _socket_.receive(__receivePacket);

    result = new byte[length = __receivePacket.getLength()];
    System.arraycopy(__receiveData, 0, result, 0, length);

    return result;
  }

}