    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017
    018package org.apache.commons.net.chargen;
    019
    020import java.io.IOException;
    021import java.net.DatagramPacket;
    022import java.net.InetAddress;
    023
    024import org.apache.commons.net.DatagramSocketClient;
    025
    026/***
    027 * The CharGenUDPClient class is a UDP implementation of a client for the
    028 * character generator protocol described in RFC 864.  It can also be
    029 * used for Systat (RFC 866), Quote of the Day (RFC 865), and netstat
    030 * (port 15).  All of these protocols involve sending a datagram to the
    031 * appropriate port, and reading data contained in one or more reply
    032 * datagrams.  The chargen and quote of the day protocols only send
    033 * one reply datagram containing 512 bytes or less of data.  The other
    034 * protocols may reply with more than one datagram, in which case you
    035 * must wait for a timeout to determine that all reply datagrams have
    036 * been sent.
    037 * <p>
    038 * To use the CharGenUDPClient class, just open a local UDP port
    039 * with {@link org.apache.commons.net.DatagramSocketClient#open  open }
    040 * and call {@link #send  send } to send the datagram that will
    041 * initiate the data reply.  For chargen or quote of the day, just
    042 * call {@link #receive  receive }, and you're done.  For netstat and
    043 * systat, call receive in a while loop, and catch a SocketException and
    044 * InterruptedIOException to detect a timeout (don't forget to set the
    045 * timeout duration beforehand).  Don't forget to call
    046 * {@link org.apache.commons.net.DatagramSocketClient#close  close() }
    047 * to clean up properly.
    048 *
    049 * @see CharGenTCPClient
    050 ***/
    051
    052public final class CharGenUDPClient extends DatagramSocketClient
    053{
    054    /*** The systat port value of 11 according to RFC 866. ***/
    055    public static final int SYSTAT_PORT = 11;
    056    /*** The netstat port value of 19. ***/
    057    public static final int NETSTAT_PORT = 15;
    058    /*** The quote of the day port value of 17 according to RFC 865. ***/
    059    public static final int QUOTE_OF_DAY_PORT = 17;
    060    /*** The character generator port value of 19 according to RFC 864. ***/
    061    public static final int CHARGEN_PORT = 19;
    062    /*** The default chargen port.  It is set to 19 according to RFC 864. ***/
    063    public static final int DEFAULT_PORT = 19;
    064
    065    private final byte[] receiveData;
    066    private final DatagramPacket receivePacket;
    067    private final DatagramPacket sendPacket;
    068
    069    /***
    070     * The default CharGenUDPClient constructor.  It initializes some internal
    071     * data structures for sending and receiving the necessary datagrams for
    072     * the chargen and related protocols.
    073     ***/
    074    public CharGenUDPClient()
    075    {
    076        // CharGen return packets have a maximum length of 512
    077        receiveData = new byte[512];
    078        receivePacket = new DatagramPacket(receiveData, receiveData.length);
    079        sendPacket = new DatagramPacket(new byte[0], 0);
    080    }
    081
    082
    083    /***
    084     * Sends the data initiation datagram.  This data in the packet is ignored
    085     * by the server, and merely serves to signal that the server should send
    086     * its reply.
    087     *
    088     * @param host The address of the server.
    089     * @param port The port of the service.
    090     * @throws IOException If an error occurs while sending the datagram.
    091     ***/
    092    public void send(final InetAddress host, final int port) throws IOException
    093    {
    094        sendPacket.setAddress(host);
    095        sendPacket.setPort(port);
    096        _socket_.send(sendPacket);
    097    }
    098
    099    /*** Same as <code>send(host, CharGenUDPClient.DEFAULT_PORT);</code>
    100     * @param host the destination host
    101     * @throws IOException on error
    102     ***/
    103    public void send(final InetAddress host) throws IOException
    104    {
    105        send(host, DEFAULT_PORT);
    106    }
    107
    108    /***
    109     * Receive the reply data from the server.  This will always be 512 bytes
    110     * or less.  Chargen and quote of the day only return one packet.  Netstat
    111     * and systat require multiple calls to receive() with timeout detection.
    112     *
    113     * @return The reply data from the server.
    114     * @throws IOException If an error occurs while receiving the datagram.
    115     ***/
    116    public byte[] receive() throws IOException
    117    {
    118        int length;
    119        byte[] result;
    120
    121        _socket_.receive(receivePacket);
    122
    123        result = new byte[length = receivePacket.getLength()];
    124        System.arraycopy(receiveData, 0, result, 0, length);
    125
    126        return result;
    127    }
    128
    129}
    130