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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 JavaDoc;
19 import java.net.DatagramPacket JavaDoc;
20 import java.net.InetAddress JavaDoc;
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 JavaDoc __receivePacket;
65     private DatagramPacket JavaDoc __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 JavaDoc(__receiveData, 512);
77         __sendPacket = new DatagramPacket JavaDoc(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 JavaDoc host, int port) throws IOException JavaDoc
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 JavaDoc host) throws IOException JavaDoc
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 JavaDoc
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
126
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