    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
    018package org.apache.commons.net.chargen;
    019
    020import java.io.IOException;
    021import java.net.DatagramPacket;
    022import java.net.InetAddress;
    023
    024import org.apache.commons.net.DatagramSocketClient;
    025import org.apache.commons.net.util.NetConstants;
    026
    027/**
    028 * 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
    029 * 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
    030 * 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
    031 * 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.
    032 * <p>
    033 * 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
    034 * } 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
    035 * 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
    036 * duration beforehand). Don't forget to call {@link org.apache.commons.net.DatagramSocketClient#close close() } to clean up properly.
    037 *
    038 * @see CharGenTCPClient
    039 */
    040
    041public final class CharGenUDPClient extends DatagramSocketClient {
    042    /** The systat port value of 11 according to RFC 866. */
    043    public static final int SYSTAT_PORT = 11;
    044    /** The netstat port value of 19. */
    045    public static final int NETSTAT_PORT = 15;
    046    /** The quote of the day port value of 17 according to RFC 865. */
    047    public static final int QUOTE_OF_DAY_PORT = 17;
    048    /** The character generator port value of 19 according to RFC 864. */
    049    public static final int CHARGEN_PORT = 19;
    050    /** The default chargen port. It is set to 19 according to RFC 864. */
    051    public static final int DEFAULT_PORT = 19;
    052
    053    private final byte[] receiveData;
    054    private final DatagramPacket receivePacket;
    055    private final DatagramPacket sendPacket;
    056
    057    /**
    058     * The default CharGenUDPClient constructor. It initializes some internal data structures for sending and receiving the necessary datagrams for the chargen
    059     * and related protocols.
    060     */
    061    public CharGenUDPClient() {
    062        // CharGen return packets have a maximum length of 512
    063        receiveData = new byte[512];
    064        receivePacket = new DatagramPacket(receiveData, receiveData.length);
    065        sendPacket = new DatagramPacket(NetConstants.EMPTY_BTYE_ARRAY, 0);
    066    }
    067
    068    /**
    069     * 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
    070     * require multiple calls to receive() with timeout detection.
    071     *
    072     * @return The reply data from the server.
    073     * @throws IOException If an error occurs while receiving the datagram.
    074     */
    075    public byte[] receive() throws IOException {
    076        final int length;
    077        final byte[] result;
    078
    079        checkOpen().receive(receivePacket);
    080
    081        result = new byte[length = receivePacket.getLength()];
    082        System.arraycopy(receiveData, 0, result, 0, length);
    083
    084        return result;
    085    }
    086
    087    /**
    088     * Same as <code>send(host, CharGenUDPClient.DEFAULT_PORT);</code>
    089     *
    090     * @param host the destination host
    091     * @throws IOException on error
    092     */
    093    public void send(final InetAddress host) throws IOException {
    094        send(host, DEFAULT_PORT);
    095    }
    096
    097    /**
    098     * 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.
    099     *
    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}