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