    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     * @author Daniel F. Savarese
    042     * @see DaytimeTCPClient
    043     ***/
    044
    045    public final class DaytimeUDPClient extends DatagramSocketClient
    046    {
    047        /*** The default daytime port.  It is set to 13 according to RFC 867. ***/
    048        public static final int DEFAULT_PORT = 13;
    049
    050        private final byte[] __dummyData = new byte[1];
    051        // Received dates should be less than 256 bytes
    052        private final byte[] __timeData = new byte[256];
    053
    054        /***
    055         * Retrieves the time string from the specified server and port and
    056         * returns it.
    057         * <p>
    058         * @param host The address of the server.
    059         * @param port The port of the service.
    060         * @return The time string.
    061         * @exception IOException If an error occurs while retrieving the time.
    062         ***/
    063        public String getTime(InetAddress host, int port) throws IOException
    064        {
    065            DatagramPacket sendPacket, receivePacket;
    066
    067            sendPacket =
    068                new DatagramPacket(__dummyData, __dummyData.length, host, port);
    069            receivePacket = new DatagramPacket(__timeData, __timeData.length);
    070
    071            _socket_.send(sendPacket);
    072            _socket_.receive(receivePacket);
    073
    074            return new String(receivePacket.getData(), 0, receivePacket.getLength());
    075        }
    076
    077        /*** Same as <code>getTime(host, DaytimeUDPClient.DEFAULT_PORT);</code> ***/
    078        public String getTime(InetAddress host) throws IOException
    079        {
    080            return getTime(host, DEFAULT_PORT);
    081        }
    082
    083    }
    084