    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.daytime;
    019
    020import java.io.IOException;
    021import java.net.DatagramPacket;
    022import java.net.InetAddress;
    023
    024import org.apache.commons.net.DatagramSocketClient;
    025
    026/**
    027 * The DaytimeUDPClient class is a UDP implementation of a client for the
    028 * Daytime protocol described in RFC 867.  To use the class, merely
    029 * open a local datagram socket with
    030 * {@link org.apache.commons.net.DatagramSocketClient#open  open }
    031 * and call {@link #getTime  getTime } to retrieve the daytime
    032 * string, then
    033 * call {@link org.apache.commons.net.DatagramSocketClient#close  close }
    034 * to close the connection properly.  Unlike
    035 * {@link org.apache.commons.net.daytime.DaytimeTCPClient},
    036 * successive calls to {@link #getTime  getTime } are permitted
    037 * without re-establishing a connection.  That is because UDP is a
    038 * connectionless protocol and the Daytime protocol is stateless.
    039 * @see DaytimeTCPClient
    040 */
    041public final class DaytimeUDPClient extends DatagramSocketClient
    042{
    043    /** The default daytime port.  It is set to 13 according to RFC 867. */
    044    public static final int DEFAULT_PORT = 13;
    045
    046    private final byte[] dummyData = new byte[1];
    047    // Received dates should be less than 256 bytes
    048    private final byte[] timeData = new byte[256];
    049
    050    /**
    051     * Retrieves the time string from the specified server and port and
    052     * returns it.
    053     *
    054     * @param host The address of the server.
    055     * @param port The port of the service.
    056     * @return The time string.
    057     * @throws IOException If an error occurs while retrieving the time.
    058     */
    059    public String getTime(final InetAddress host, final int port) throws IOException
    060    {
    061        final DatagramPacket sendPacket;
    062        final DatagramPacket receivePacket;
    063
    064        sendPacket =
    065            new DatagramPacket(dummyData, dummyData.length, host, port);
    066        receivePacket = new DatagramPacket(timeData, timeData.length);
    067
    068        _socket_.send(sendPacket);
    069        _socket_.receive(receivePacket);
    070
    071        return new String(receivePacket.getData(), 0, receivePacket.getLength(), getCharset()); // Java 1.6 can use getCharset()
    072    }
    073
    074    /** Same as <code>getTime(host, DaytimeUDPClient.DEFAULT_PORT);</code>
    075     * @param host the host
    076     * @return  the time
    077     * @throws IOException on error
    078     */
    079    public String getTime(final InetAddress host) throws IOException
    080    {
    081        return getTime(host, DEFAULT_PORT);
    082    }
    083
    084}
    085