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    1   package org.apache.commons.net;
    2
    3   /* ====================================================================
    4    * The Apache Software License, Version 1.1
    5    *
    6    * Copyright (c) 2001 The Apache Software Foundation.  All rights
    7    * reserved.
    8    *
    9    * Redistribution and use in source and binary forms, with or without
    10   * modification, are permitted provided that the following conditions
    11   * are met:
    12   *
    13   * 1. Redistributions of source code must retain the above copyright
    14   *    notice, this list of conditions and the following disclaimer.
    15   *
    16   * 2. Redistributions in binary form must reproduce the above copyright
    17   *    notice, this list of conditions and the following disclaimer in
    18   *    the documentation and/or other materials provided with the
    19   *    distribution.
    20   *
    21   * 3. The end-user documentation included with the redistribution,
    22   *    if any, must include the following acknowledgment:
    23   *       "This product includes software developed by the
    24   *        Apache Software Foundation (http://www.apache.org/)."
    25   *    Alternately, this acknowledgment may appear in the software itself,
    26   *    if and wherever such third-party acknowledgments normally appear.
    27   *
    28   * 4. The names "Apache" and "Apache Software Foundation" and
    29   *    "Apache Commons" must not be used to endorse or promote products
    30   *    derived from this software without prior written permission. For
    31   *    written permission, please contact apache@apache.org.
    32   *
    33   * 5. Products derived from this software may not be called "Apache",
    34   *    nor may "Apache" appear in their name, without
    35   *    prior written permission of the Apache Software Foundation.
    36   *
    37   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
    38   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
    39   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
    40   * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
    41   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    42   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
    43   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
    44   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
    45   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
    46   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
    47   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
    48   * SUCH DAMAGE.
    49   * ====================================================================
    50   *
    51   * This software consists of voluntary contributions made by many
    52   * individuals on behalf of the Apache Software Foundation.  For more
    53   * information on the Apache Software Foundation, please see
    54   * <http://www.apache.org/>;.
    55   */
    56
    57  import java.io.IOException;
    58  import java.net.DatagramPacket;
    59  import java.net.InetAddress;
    60
    61  /****
    62   * The DaytimeUDPClient class is a UDP implementation of a client for the
    63   * Daytime protocol described in RFC 867.  To use the class, merely
    64   * open a local datagram socket with
    65   * <a href="org.apache.commons.net.DatagramSocketClient.html#open"> open </a>
    66   * and call <a href="#getTime"> getTime </a> to retrieve the daytime
    67   * string, then
    68   * call <a href="org.apache.commons.net.DatagramSocketClient.html#close"> close </a>
    69   * to close the connection properly.  Unlike
    70   * <a href="org.apache.commons.net.DaytimeTCPClient.html"> DaytimeTCPClient </a>,
    71   * successive calls to <a href="#getTime"> getTime </a> are permitted
    72   * without re-establishing a connection.  That is because UDP is a
    73   * connectionless protocol and the Daytime protocol is stateless.
    74   * <p>
    75   * <p>
    76   * @author Daniel F. Savarese
    77   * @see DaytimeTCPClient
    78   ***/
    79
    80  public final class DaytimeUDPClient extends DatagramSocketClient
    81  {
    82      /**** The default daytime port.  It is set to 13 according to RFC 867. ***/
    83      public static final int DEFAULT_PORT = 13;
    84
    85      private byte[] __dummyData = new byte[1];
    86      // Received dates should be less than 256 bytes
    87      private byte[] __timeData = new byte[256];
    88
    89      /****
    90       * Retrieves the time string from the specified server and port and
    91       * returns it.
    92       * <p>
    93       * @param host The address of the server.
    94       * @param port The port of the service.
    95       * @return The time string.
    96       * @exception IOException If an error occurs while retrieving the time.
    97       ***/
    98      public String getTime(InetAddress host, int port) throws IOException
    99      {
    100         DatagramPacket sendPacket, receivePacket;
    101
    102         sendPacket =
    103             new DatagramPacket(__dummyData, __dummyData.length, host, port);
    104         receivePacket = new DatagramPacket(__timeData, __timeData.length);
    105
    106         _socket_.send(sendPacket);
    107         _socket_.receive(receivePacket);
    108
    109         return new String(receivePacket.getData(), 0, receivePacket.getLength());
    110     }
    111
    112     /**** Same as <code>getTime(host, DaytimeUDPClient.DEFAULT_PORT);</code> ***/
    113     public String getTime(InetAddress host) throws IOException
    114     {
    115         return getTime(host, DEFAULT_PORT);
    116     }
    117
    118 }
    119

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