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(InetAddress host, int port) throws IOException
060    {
061        DatagramPacket sendPacket, receivePacket;
062
063        sendPacket =
064            new DatagramPacket(__dummyData, __dummyData.length, host, port);
065        receivePacket = new DatagramPacket(__timeData, __timeData.length);
066
067        _socket_.send(sendPacket);
068        _socket_.receive(receivePacket);
069
070        return new String(receivePacket.getData(), 0, receivePacket.getLength(), getCharsetName()); // Java 1.6 can use getCharset()
071    }
072
073    /** Same as <code>getTime(host, DaytimeUDPClient.DEFAULT_PORT);</code>
074     * @param host the host
075     * @return  the time
076     * @throws IOException on error
077     */
078    public String getTime(InetAddress host) throws IOException
079    {
080        return getTime(host, DEFAULT_PORT);
081    }
082
083}
084