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