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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  
18  package org.apache.commons.net.chargen;
19  
20  import java.io.IOException;
21  import java.net.DatagramPacket;
22  import java.net.InetAddress;
23  
24  import org.apache.commons.net.DatagramSocketClient;
25  
26  /***
27   * The CharGenUDPClient class is a UDP implementation of a client for the
28   * character generator protocol described in RFC 864.  It can also be
29   * used for Systat (RFC 866), Quote of the Day (RFC 865), and netstat
30   * (port 15).  All of these protocols involve sending a datagram to the
31   * appropriate port, and reading data contained in one or more reply
32   * datagrams.  The chargen and quote of the day protocols only send
33   * one reply datagram containing 512 bytes or less of data.  The other
34   * protocols may reply with more than one datagram, in which case you
35   * must wait for a timeout to determine that all reply datagrams have
36   * been sent.
37   * <p>
38   * To use the CharGenUDPClient class, just open a local UDP port
39   * with {@link org.apache.commons.net.DatagramSocketClient#open  open }
40   * and call {@link #send  send } to send the datagram that will
41   * initiate the data reply.  For chargen or quote of the day, just
42   * call {@link #receive  receive }, and you're done.  For netstat and
43   * systat, call receive in a while loop, and catch a SocketException and
44   * InterruptedIOException to detect a timeout (don't forget to set the
45   * timeout duration beforehand).  Don't forget to call
46   * {@link org.apache.commons.net.DatagramSocketClient#close  close() }
47   * to clean up properly.
48   * <p>
49   * <p>
50   * @see CharGenTCPClient
51   ***/
52  
53  public final class CharGenUDPClient extends DatagramSocketClient
54  {
55      /*** The systat port value of 11 according to RFC 866. ***/
56      public static final int SYSTAT_PORT = 11;
57      /*** The netstat port value of 19. ***/
58      public static final int NETSTAT_PORT = 15;
59      /*** The quote of the day port value of 17 according to RFC 865. ***/
60      public static final int QUOTE_OF_DAY_PORT = 17;
61      /*** The character generator port value of 19 according to RFC 864. ***/
62      public static final int CHARGEN_PORT = 19;
63      /*** The default chargen port.  It is set to 19 according to RFC 864. ***/
64      public static final int DEFAULT_PORT = 19;
65  
66      private final byte[] __receiveData;
67      private final DatagramPacket __receivePacket;
68      private final DatagramPacket __sendPacket;
69  
70      /***
71       * The default CharGenUDPClient constructor.  It initializes some internal
72       * data structures for sending and receiving the necessary datagrams for
73       * the chargen and related protocols.
74       ***/
75      public CharGenUDPClient()
76      {
77          // CharGen return packets have a maximum length of 512
78          __receiveData = new byte[512];
79          __receivePacket = new DatagramPacket(__receiveData, __receiveData.length);
80          __sendPacket = new DatagramPacket(new byte[0], 0);
81      }
82  
83  
84      /***
85       * Sends the data initiation datagram.  This data in the packet is ignored
86       * by the server, and merely serves to signal that the server should send
87       * its reply.
88       * <p>
89       * @param host The address of the server.
90       * @param port The port of the service.
91       * @exception IOException If an error occurs while sending the datagram.
92       ***/
93      public void send(InetAddress host, int port) throws IOException
94      {
95          __sendPacket.setAddress(host);
96          __sendPacket.setPort(port);
97          _socket_.send(__sendPacket);
98      }
99  
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