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