    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;
    025import org.apache.commons.net.util.NetConstants;
    026
    027/**
    028 * The CharGenUDPClient class is a UDP implementation of a client for the
    029 * character generator protocol described in RFC 864.  It can also be
    030 * used for Systat (RFC 866), Quote of the Day (RFC 865), and netstat
    031 * (port 15).  All of these protocols involve sending a datagram to the
    032 * appropriate port, and reading data contained in one or more reply
    033 * datagrams.  The chargen and quote of the day protocols only send
    034 * one reply datagram containing 512 bytes or less of data.  The other
    035 * protocols may reply with more than one datagram, in which case you
    036 * must wait for a timeout to determine that all reply datagrams have
    037 * been sent.
    038 * <p>
    039 * To use the CharGenUDPClient class, just open a local UDP port
    040 * with {@link org.apache.commons.net.DatagramSocketClient#open  open }
    041 * and call {@link #send  send } to send the datagram that will
    042 * initiate the data reply.  For chargen or quote of the day, just
    043 * call {@link #receive  receive }, and you're done.  For netstat and
    044 * systat, call receive in a while loop, and catch a SocketException and
    045 * InterruptedIOException to detect a timeout (don't forget to set the
    046 * timeout duration beforehand).  Don't forget to call
    047 * {@link org.apache.commons.net.DatagramSocketClient#close  close() }
    048 * to clean up properly.
    049 *
    050 * @see CharGenTCPClient
    051 */
    052
    053public final class CharGenUDPClient extends DatagramSocketClient
    054{
    055    /** The systat port value of 11 according to RFC 866. */
    056    public static final int SYSTAT_PORT = 11;
    057    /** The netstat port value of 19. */
    058    public static final int NETSTAT_PORT = 15;
    059    /** The quote of the day port value of 17 according to RFC 865. */
    060    public static final int QUOTE_OF_DAY_PORT = 17;
    061    /** The character generator port value of 19 according to RFC 864. */
    062    public static final int CHARGEN_PORT = 19;
    063    /** The default chargen port.  It is set to 19 according to RFC 864. */
    064    public static final int DEFAULT_PORT = 19;
    065
    066    private final byte[] receiveData;
    067    private final DatagramPacket receivePacket;
    068    private final DatagramPacket sendPacket;
    069
    070    /**
    071     * The default CharGenUDPClient constructor.  It initializes some internal
    072     * data structures for sending and receiving the necessary datagrams for
    073     * the chargen and related protocols.
    074     */
    075    public CharGenUDPClient()
    076    {
    077        // CharGen return packets have a maximum length of 512
    078        receiveData = new byte[512];
    079        receivePacket = new DatagramPacket(receiveData, receiveData.length);
    080        sendPacket = new DatagramPacket(NetConstants.EMPTY_BTYE_ARRAY, 0);
    081    }
    082
    083
    084    /**
    085     * Sends the data initiation datagram.  This data in the packet is ignored
    086     * by the server, and merely serves to signal that the server should send
    087     * its reply.
    088     *
    089     * @param host The address of the server.
    090     * @param port The port of the service.
    091     * @throws IOException If an error occurs while sending the datagram.
    092     */
    093    public void send(final InetAddress host, final int port) throws IOException
    094    {
    095        sendPacket.setAddress(host);
    096        sendPacket.setPort(port);
    097        _socket_.send(sendPacket);
    098    }
    099
    100    /** Same as <code>send(host, CharGenUDPClient.DEFAULT_PORT);</code>
    101     * @param host the destination host
    102     * @throws IOException on error
    103     */
    104    public void send(final InetAddress host) throws IOException
    105    {
    106        send(host, DEFAULT_PORT);
    107    }
    108
    109    /**
    110     * Receive the reply data from the server.  This will always be 512 bytes
    111     * or less.  Chargen and quote of the day only return one packet.  Netstat
    112     * and systat require multiple calls to receive() with timeout detection.
    113     *
    114     * @return The reply data from the server.
    115     * @throws IOException If an error occurs while receiving the datagram.
    116     */
    117    public byte[] receive() throws IOException
    118    {
    119        final int length;
    120        final byte[] result;
    121
    122        _socket_.receive(receivePacket);
    123
    124        result = new byte[length = receivePacket.getLength()];
    125        System.arraycopy(receiveData, 0, result, 0, length);
    126
    127        return result;
    128    }
    129
    130}
    131