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What this is

This file is included in the "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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The source code

 * Copyright 2001-2004 The Apache Software Foundation
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * See the License for the specific language governing permissions and
 * limitations under the License.

 * 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 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 contained in one or more reply
 * datagrams.  The chargen and quote of the day protocols only send
 * one reply datagram containing 512 bytes or less of data.  The 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.

* To use the CharGenUDPClient class, just open a local UDP port * with open * and call send to send the datagram that will * initiate the data reply. For chargen or quote of the day, just * call receive , and you're done. For netstat 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 duration beforehand). Don't forget to call * close() * to clean up properly. *


* @author Daniel F. Savarese * @see CharGenTCPClient ***/ public final class CharGenUDPClient extends DatagramSocketClient { /*** The systat port value of 11 according to RFC 866. ***/ public static final int SYSTAT_PORT = 11; /*** The netstat port value of 19. ***/ public static final int NETSTAT_PORT = 15; /*** The quote of the day port value of 17 according to RFC 865. ***/ public static final int QUOTE_OF_DAY_PORT = 17; /*** The character generator port value of 19 according to RFC 864. ***/ public static final int CHARGEN_PORT = 19; /*** The default chargen port. It is set to 19 according to RFC 864. ***/ public static final int DEFAULT_PORT = 19; private byte[] __receiveData; private DatagramPacket __receivePacket; private DatagramPacket __sendPacket; /*** * The default CharGenUDPClient constructor. It initializes some internal * data structures for sending and receiving the necessary datagrams for * the chargen and related protocols. ***/ public CharGenUDPClient() { // CharGen return packets have a maximum length of 512 __receiveData = new byte[512]; __receivePacket = new DatagramPacket(__receiveData, 512); __sendPacket = new DatagramPacket(new byte[0], 0); } /*** * 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. *

* @param host The address of the server. * @param port The port of the service. * @exception IOException If an error occurs while sending the datagram. ***/ public void send(InetAddress host, int port) throws IOException { __sendPacket.setAddress(host); __sendPacket.setPort(port); _socket_.send(__sendPacket); } /*** Same as send(host, CharGenUDPClient.DEFAULT_PORT); ***/ public void send(InetAddress host) throws IOException { send(host, DEFAULT_PORT); } /*** * Receive the reply data from the server. This will always be 512 bytes * or less. Chargen and quote of the day only return one packet. Netstat * and systat require multiple calls to receive() with timeout detection. *

* @return The reply data from the server. * @exception IOException If an error occurs while receiving the datagram. ***/ public byte[] receive() throws IOException { int length; byte[] result; _socket_.receive(__receivePacket); result = new byte[length = __receivePacket.getLength()]; System.arraycopy(__receiveData, 0, result, 0, length); return result; } }

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