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 package org.apache.commons.net;
18
19 import java.io.IOException;
20 import java.net.DatagramPacket;
21 import java.net.InetAddress;
22
23 /***
24 * The CharGenUDPClient class is a UDP implementation of a client for the
25 * character generator protocol described in RFC 864. It can also be
26 * used for Systat (RFC 866), Quote of the Day (RFC 865), and netstat
27 * (port 15). All of these protocols involve sending a datagram to the
28 * appropriate port, and reading data contained in one or more reply
29 * datagrams. The chargen and quote of the day protocols only send
30 * one reply datagram containing 512 bytes or less of data. The other
31 * protocols may reply with more than one datagram, in which case you
32 * must wait for a timeout to determine that all reply datagrams have
33 * been sent.
34 * <p>
35 * To use the CharGenUDPClient class, just open a local UDP port
36 * with {@link org.apache.commons.net.DatagramSocketClient#open open }
37 * and call {@link #send send } to send the datagram that will
38 * initiate the data reply. For chargen or quote of the day, just
39 * call {@link #receive receive }, and you're done. For netstat and
40 * systat, call receive in a while loop, and catch a SocketException and
41 * InterruptedIOException to detect a timeout (don't forget to set the
42 * timeout duration beforehand). Don't forget to call
43 * {@link org.apache.commons.net.DatagramSocketClient#close close() }
44 * to clean up properly.
45 * <p>
46 * <p>
47 * @author Daniel F. Savarese
48 * @see CharGenTCPClient
49 ***/
50
51 public final class CharGenUDPClient extends DatagramSocketClient
52 {
53 /*** The systat port value of 11 according to RFC 866. ***/
54 public static final int SYSTAT_PORT = 11;
55 /*** The netstat port value of 19. ***/
56 public static final int NETSTAT_PORT = 15;
57 /*** The quote of the day port value of 17 according to RFC 865. ***/
58 public static final int QUOTE_OF_DAY_PORT = 17;
59 /*** The character generator port value of 19 according to RFC 864. ***/
60 public static final int CHARGEN_PORT = 19;
61 /*** The default chargen port. It is set to 19 according to RFC 864. ***/
62 public static final int DEFAULT_PORT = 19;
63
64 private byte[] __receiveData;
65 private DatagramPacket __receivePacket;
66 private DatagramPacket __sendPacket;
67
68 /***
69 * The default CharGenUDPClient constructor. It initializes some internal
70 * data structures for sending and receiving the necessary datagrams for
71 * the chargen and related protocols.
72 ***/
73 public CharGenUDPClient()
74 {
75 // CharGen return packets have a maximum length of 512
76 __receiveData = new byte[512];
77 __receivePacket = new DatagramPacket(__receiveData, 512);
78 __sendPacket = new DatagramPacket(new byte[0], 0);
79 }
80
81
82 /***
83 * Sends the data initiation datagram. This data in the packet is ignored
84 * by the server, and merely serves to signal that the server should send
85 * its reply.
86 * <p>
87 * @param host The address of the server.
88 * @param port The port of the service.
89 * @exception IOException If an error occurs while sending the datagram.
90 ***/
91 public void send(InetAddress host, int port) throws IOException
92 {
93 __sendPacket.setAddress(host);
94 __sendPacket.setPort(port);
95 _socket_.send(__sendPacket);
96 }
97
98 /*** Same as <code>send(host, CharGenUDPClient.DEFAULT_PORT);</code> ***/
99 public void send(InetAddress host) throws IOException
100 {
101 send(host, DEFAULT_PORT);
102 }
103
104 /***
105 * Receive the reply data from the server. This will always be 512 bytes
106 * or less. Chargen and quote of the day only return one packet. Netstat
107 * and systat require multiple calls to receive() with timeout detection.
108 * <p>
109 * @return The reply data from the server.
110 * @exception IOException If an error occurs while receiving the datagram.
111 ***/
112 public byte[] receive() throws IOException
113 {
114 int length;
115 byte[] result;
116
117 _socket_.receive(__receivePacket);
118
119 result = new byte[length = __receivePacket.getLength()];
120 System.arraycopy(__receiveData, 0, result, 0, length);
121
122 return result;
123 }
124
125 }
126