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    
018    package org.apache.commons.net.chargen;
019    
020    import java.io.IOException;
021    import java.net.DatagramPacket;
022    import java.net.InetAddress;
023    
024    import 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     * <p>
049     * <p>
050     * @author Daniel F. Savarese
051     * @see CharGenTCPClient
052     ***/
053    
054    public final class CharGenUDPClient extends DatagramSocketClient
055    {
056        /*** The systat port value of 11 according to RFC 866. ***/
057        public static final int SYSTAT_PORT = 11;
058        /*** The netstat port value of 19. ***/
059        public static final int NETSTAT_PORT = 15;
060        /*** The quote of the day port value of 17 according to RFC 865. ***/
061        public static final int QUOTE_OF_DAY_PORT = 17;
062        /*** The character generator port value of 19 according to RFC 864. ***/
063        public static final int CHARGEN_PORT = 19;
064        /*** The default chargen port.  It is set to 19 according to RFC 864. ***/
065        public static final int DEFAULT_PORT = 19;
066    
067        private final byte[] __receiveData;
068        private final DatagramPacket __receivePacket;
069        private final DatagramPacket __sendPacket;
070    
071        /***
072         * The default CharGenUDPClient constructor.  It initializes some internal
073         * data structures for sending and receiving the necessary datagrams for
074         * the chargen and related protocols.
075         ***/
076        public CharGenUDPClient()
077        {
078            // CharGen return packets have a maximum length of 512
079            __receiveData = new byte[512];
080            __receivePacket = new DatagramPacket(__receiveData, __receiveData.length);
081            __sendPacket = new DatagramPacket(new byte[0], 0);
082        }
083    
084    
085        /***
086         * Sends the data initiation datagram.  This data in the packet is ignored
087         * by the server, and merely serves to signal that the server should send
088         * its reply.
089         * <p>
090         * @param host The address of the server.
091         * @param port The port of the service.
092         * @exception IOException If an error occurs while sending the datagram.
093         ***/
094        public void send(InetAddress host, int port) throws IOException
095        {
096            __sendPacket.setAddress(host);
097            __sendPacket.setPort(port);
098            _socket_.send(__sendPacket);
099        }
100    
101        /*** Same as <code>send(host, CharGenUDPClient.DEFAULT_PORT);</code> ***/
102        public void send(InetAddress host) throws IOException
103        {
104            send(host, DEFAULT_PORT);
105        }
106    
107        /***
108         * Receive the reply data from the server.  This will always be 512 bytes
109         * or less.  Chargen and quote of the day only return one packet.  Netstat
110         * and systat require multiple calls to receive() with timeout detection.
111         * <p>
112         * @return The reply data from the server.
113         * @exception IOException If an error occurs while receiving the datagram.
114         ***/
115        public byte[] receive() throws IOException
116        {
117            int length;
118            byte[] result;
119    
120            _socket_.receive(__receivePacket);
121    
122            result = new byte[length = __receivePacket.getLength()];
123            System.arraycopy(__receiveData, 0, result, 0, length);
124    
125            return result;
126        }
127    
128    }
129