001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018 package org.apache.commons.net.chargen;
019
020 import java.io.IOException;
021 import java.net.DatagramPacket;
022 import java.net.InetAddress;
023
024 import org.apache.commons.net.DatagramSocketClient;
025
026 /***
027 * The CharGenUDPClient class is a UDP implementation of a client for the
028 * character generator protocol described in RFC 864. It can also be
029 * used for Systat (RFC 866), Quote of the Day (RFC 865), and netstat
030 * (port 15). All of these protocols involve sending a datagram to the
031 * appropriate port, and reading data contained in one or more reply
032 * datagrams. The chargen and quote of the day protocols only send
033 * one reply datagram containing 512 bytes or less of data. The other
034 * protocols may reply with more than one datagram, in which case you
035 * must wait for a timeout to determine that all reply datagrams have
036 * been sent.
037 * <p>
038 * To use the CharGenUDPClient class, just open a local UDP port
039 * with {@link org.apache.commons.net.DatagramSocketClient#open open }
040 * and call {@link #send send } to send the datagram that will
041 * initiate the data reply. For chargen or quote of the day, just
042 * call {@link #receive receive }, and you're done. For netstat and
043 * systat, call receive in a while loop, and catch a SocketException and
044 * InterruptedIOException to detect a timeout (don't forget to set the
045 * timeout duration beforehand). Don't forget to call
046 * {@link org.apache.commons.net.DatagramSocketClient#close close() }
047 * to clean up properly.
048 * <p>
049 * <p>
050 * @author Daniel F. Savarese
051 * @see CharGenTCPClient
052 ***/
053
054 public final class CharGenUDPClient extends DatagramSocketClient
055 {
056 /*** The systat port value of 11 according to RFC 866. ***/
057 public static final int SYSTAT_PORT = 11;
058 /*** The netstat port value of 19. ***/
059 public static final int NETSTAT_PORT = 15;
060 /*** The quote of the day port value of 17 according to RFC 865. ***/
061 public static final int QUOTE_OF_DAY_PORT = 17;
062 /*** The character generator port value of 19 according to RFC 864. ***/
063 public static final int CHARGEN_PORT = 19;
064 /*** The default chargen port. It is set to 19 according to RFC 864. ***/
065 public static final int DEFAULT_PORT = 19;
066
067 private byte[] __receiveData;
068 private DatagramPacket __receivePacket;
069 private DatagramPacket __sendPacket;
070
071 /***
072 * The default CharGenUDPClient constructor. It initializes some internal
073 * data structures for sending and receiving the necessary datagrams for
074 * the chargen and related protocols.
075 ***/
076 public CharGenUDPClient()
077 {
078 // CharGen return packets have a maximum length of 512
079 __receiveData = new byte[512];
080 __receivePacket = new DatagramPacket(__receiveData, 512);
081 __sendPacket = new DatagramPacket(new byte[0], 0);
082 }
083
084
085 /***
086 * Sends the data initiation datagram. This data in the packet is ignored
087 * by the server, and merely serves to signal that the server should send
088 * its reply.
089 * <p>
090 * @param host The address of the server.
091 * @param port The port of the service.
092 * @exception IOException If an error occurs while sending the datagram.
093 ***/
094 public void send(InetAddress host, int port) throws IOException
095 {
096 __sendPacket.setAddress(host);
097 __sendPacket.setPort(port);
098 _socket_.send(__sendPacket);
099 }
100
101 /*** Same as <code>send(host, CharGenUDPClient.DEFAULT_PORT);</code> ***/
102 public void send(InetAddress host) throws IOException
103 {
104 send(host, DEFAULT_PORT);
105 }
106
107 /***
108 * Receive the reply data from the server. This will always be 512 bytes
109 * or less. Chargen and quote of the day only return one packet. Netstat
110 * and systat require multiple calls to receive() with timeout detection.
111 * <p>
112 * @return The reply data from the server.
113 * @exception IOException If an error occurs while receiving the datagram.
114 ***/
115 public byte[] receive() throws IOException
116 {
117 int length;
118 byte[] result;
119
120 _socket_.receive(__receivePacket);
121
122 result = new byte[length = __receivePacket.getLength()];
123 System.arraycopy(__receiveData, 0, result, 0, length);
124
125 return result;
126 }
127
128 }
129