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