    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
    018    package org.apache.commons.net.daytime;
    019
    020    import java.io.IOException;
    021    import java.net.DatagramPacket;
    022    import java.net.InetAddress;
    023
    024    import 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     * <p>
    040     * <p>
    041     * @see DaytimeTCPClient
    042     ***/
    043
    044    public final class DaytimeUDPClient extends DatagramSocketClient
    045    {
    046        /*** The default daytime port.  It is set to 13 according to RFC 867. ***/
    047        public static final int DEFAULT_PORT = 13;
    048
    049        private final byte[] __dummyData = new byte[1];
    050        // Received dates should be less than 256 bytes
    051        private final byte[] __timeData = new byte[256];
    052
    053        /***
    054         * Retrieves the time string from the specified server and port and
    055         * returns it.
    056         * <p>
    057         * @param host The address of the server.
    058         * @param port The port of the service.
    059         * @return The time string.
    060         * @exception IOException If an error occurs while retrieving the time.
    061         ***/
    062        public String getTime(InetAddress host, int port) throws IOException
    063        {
    064            DatagramPacket sendPacket, receivePacket;
    065
    066            sendPacket =
    067                new DatagramPacket(__dummyData, __dummyData.length, host, port);
    068            receivePacket = new DatagramPacket(__timeData, __timeData.length);
    069
    070            _socket_.send(sendPacket);
    071            _socket_.receive(receivePacket);
    072
    073            return new String(receivePacket.getData(), 0, receivePacket.getLength());
    074        }
    075
    076        /*** Same as <code>getTime(host, DaytimeUDPClient.DEFAULT_PORT);</code> ***/
    077        public String getTime(InetAddress host) throws IOException
    078        {
    079            return getTime(host, DEFAULT_PORT);
    080        }
    081
    082    }
    083