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1   /*
2    * Copyright 2001-2005 The Apache Software Foundation
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    *     http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  package org.apache.commons.net;
17  
18  import java.io.IOException;
19  import java.net.DatagramPacket;
20  import java.net.InetAddress;
21  
22  /***
23   * The CharGenUDPClient class is a UDP implementation of a client for the
24   * character generator protocol described in RFC 864.  It can also be
25   * used for Systat (RFC 866), Quote of the Day (RFC 865), and netstat
26   * (port 15).  All of these protocols involve sending a datagram to the
27   * appropriate port, and reading data contained in one or more reply
28   * datagrams.  The chargen and quote of the day protocols only send
29   * one reply datagram containing 512 bytes or less of data.  The other
30   * protocols may reply with more than one datagram, in which case you
31   * must wait for a timeout to determine that all reply datagrams have
32   * been sent.
33   * <p>
34   * To use the CharGenUDPClient class, just open a local UDP port
35   * with {@link org.apache.commons.net.DatagramSocketClient#open  open }
36   * and call {@link #send  send } to send the datagram that will
37   * initiate the data reply.  For chargen or quote of the day, just
38   * call {@link #receive  receive }, and you're done.  For netstat and
39   * systat, call receive in a while loop, and catch a SocketException and
40   * InterruptedIOException to detect a timeout (don't forget to set the
41   * timeout duration beforehand).  Don't forget to call
42   * {@link org.apache.commons.net.DatagramSocketClient#close  close() }
43   * to clean up properly.
44   * <p>
45   * <p>
46   * @author Daniel F. Savarese
47   * @see CharGenTCPClient
48   ***/
49  
50  public final class CharGenUDPClient extends DatagramSocketClient
51  {
52      /*** The systat port value of 11 according to RFC 866. ***/
53      public static final int SYSTAT_PORT = 11;
54      /*** The netstat port value of 19. ***/
55      public static final int NETSTAT_PORT = 15;
56      /*** The quote of the day port value of 17 according to RFC 865. ***/
57      public static final int QUOTE_OF_DAY_PORT = 17;
58      /*** The character generator port value of 19 according to RFC 864. ***/
59      public static final int CHARGEN_PORT = 19;
60      /*** The default chargen port.  It is set to 19 according to RFC 864. ***/
61      public static final int DEFAULT_PORT = 19;
62  
63      private byte[] __receiveData;
64      private DatagramPacket __receivePacket;
65      private DatagramPacket __sendPacket;
66  
67      /***
68       * The default CharGenUDPClient constructor.  It initializes some internal
69       * data structures for sending and receiving the necessary datagrams for
70       * the chargen and related protocols.
71       ***/
72      public CharGenUDPClient()
73      {
74          // CharGen return packets have a maximum length of 512
75          __receiveData = new byte[512];
76          __receivePacket = new DatagramPacket(__receiveData, 512);
77          __sendPacket = new DatagramPacket(new byte[0], 0);
78      }
79  
80  
81      /***
82       * Sends the data initiation datagram.  This data in the packet is ignored
83       * by the server, and merely serves to signal that the server should send
84       * its reply.
85       * <p>
86       * @param host The address of the server.
87       * @param port The port of the service.
88       * @exception IOException If an error occurs while sending the datagram.
89       ***/
90      public void send(InetAddress host, int port) throws IOException
91      {
92          __sendPacket.setAddress(host);
93          __sendPacket.setPort(port);
94          _socket_.send(__sendPacket);
95      }
96  
97      /*** Same as <code>send(host, CharGenUDPClient.DEFAULT_PORT);</code> ***/
98      public void send(InetAddress host) throws IOException
99      {
100         send(host, DEFAULT_PORT);
101     }
102 
103     /***
104      * Receive the reply data from the server.  This will always be 512 bytes
105      * or less.  Chargen and quote of the day only return one packet.  Netstat
106      * and systat require multiple calls to receive() with timeout detection.
107      * <p>
108      * @return The reply data from the server.
109      * @exception IOException If an error occurs while receiving the datagram.
110      ***/
111     public byte[] receive() throws IOException
112     {
113         int length;
114         byte[] result;
115 
116         _socket_.receive(__receivePacket);
117 
118         result = new byte[length = __receivePacket.getLength()];
119         System.arraycopy(__receiveData, 0, result, 0, length);
120 
121         return result;
122     }
123 
124 }
125