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 41 public final class CharGenUDPClient extends DatagramSocketClient { 42 /** The systat port value of 11 according to RFC 866. */ 43 public static final int SYSTAT_PORT = 11; 44 /** The netstat port value of 19. */ 45 public static final int NETSTAT_PORT = 15; 46 /** The quote of the day port value of 17 according to RFC 865. */ 47 public static final int QUOTE_OF_DAY_PORT = 17; 48 /** The character generator port value of 19 according to RFC 864. */ 49 public static final int CHARGEN_PORT = 19; 50 /** The default chargen port. It is set to 19 according to RFC 864. */ 51 public static final int DEFAULT_PORT = 19; 52 53 private final byte[] receiveData; 54 private final DatagramPacket receivePacket; 55 private final DatagramPacket sendPacket; 56 57 /** 58 * The default CharGenUDPClient constructor. It initializes some internal data structures for sending and receiving the necessary datagrams for the chargen 59 * and related protocols. 60 */ 61 public CharGenUDPClient() { 62 // CharGen return packets have a maximum length of 512 63 receiveData = new byte[512]; 64 receivePacket = new DatagramPacket(receiveData, receiveData.length); 65 sendPacket = new DatagramPacket(NetConstants.EMPTY_BTYE_ARRAY, 0); 66 } 67 68 /** 69 * 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 70 * require multiple calls to receive() with timeout detection. 71 * 72 * @return The reply data from the server. 73 * @throws IOException If an error occurs while receiving the datagram. 74 */ 75 public byte[] receive() throws IOException { 76 final int length; 77 final byte[] result; 78 79 checkOpen().receive(receivePacket); 80 81 result = new byte[length = receivePacket.getLength()]; 82 System.arraycopy(receiveData, 0, result, 0, length); 83 84 return result; 85 } 86 87 /** 88 * Same as <code>send(host, CharGenUDPClient.DEFAULT_PORT);</code> 89 * 90 * @param host the destination host 91 * @throws IOException on error 92 */ 93 public void send(final InetAddress host) throws IOException { 94 send(host, DEFAULT_PORT); 95 } 96 97 /** 98 * 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. 99 * 100 * @param host The address of the server. 101 * @param port The port of the service. 102 * @throws IOException If an error occurs while sending the datagram. 103 */ 104 public void send(final InetAddress host, final int port) throws IOException { 105 sendPacket.setAddress(host); 106 sendPacket.setPort(port); 107 checkOpen().send(sendPacket); 108 } 109 110 }