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 * @see CharGenTCPClient
051 ***/
052
053 public 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(new byte[0], 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 * <p>
089 * @param host The address of the server.
090 * @param port The port of the service.
091 * @exception IOException If an error occurs while sending the datagram.
092 ***/
093 public void send(InetAddress host, 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 public void send(InetAddress host) throws IOException
102 {
103 send(host, DEFAULT_PORT);
104 }
105
106 /***
107 * Receive the reply data from the server. This will always be 512 bytes
108 * or less. Chargen and quote of the day only return one packet. Netstat
109 * and systat require multiple calls to receive() with timeout detection.
110 * <p>
111 * @return The reply data from the server.
112 * @exception IOException If an error occurs while receiving the datagram.
113 ***/
114 public byte[] receive() throws IOException
115 {
116 int length;
117 byte[] result;
118
119 _socket_.receive(__receivePacket);
120
121 result = new byte[length = __receivePacket.getLength()];
122 System.arraycopy(__receiveData, 0, result, 0, length);
123
124 return result;
125 }
126
127 }
128