    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.time;
    019
    020    import java.io.IOException;
    021    import java.net.DatagramPacket;
    022    import java.net.InetAddress;
    023    import java.util.Date;
    024
    025    import org.apache.commons.net.DatagramSocketClient;
    026
    027    /***
    028     * The TimeUDPClient class is a UDP implementation of a client for the
    029     * Time protocol described in RFC 868.  To use the class, merely
    030     * open a local datagram socket with
    031     * {@link org.apache.commons.net.DatagramSocketClient#open  open }
    032     * and call {@link #getTime  getTime } or
    033     * {@link #getTime  getDate } to retrieve the time. Then call
    034     * {@link org.apache.commons.net.DatagramSocketClient#close  close }
    035     * to close the connection properly.  Unlike
    036     * {@link org.apache.commons.net.time.TimeTCPClient},
    037     * successive calls to {@link #getTime  getTime } or
    038     * {@link #getDate  getDate } are permitted
    039     * without re-establishing a connection.  That is because UDP is a
    040     * connectionless protocol and the Time protocol is stateless.
    041     * <p>
    042     * <p>
    043     * @author Daniel F. Savarese
    044     * @see TimeTCPClient
    045     ***/
    046
    047    public final class TimeUDPClient extends DatagramSocketClient
    048    {
    049        /*** The default time port.  It is set to 37 according to RFC 868. ***/
    050        public static final int DEFAULT_PORT = 37;
    051
    052        /***
    053         * The number of seconds between 00:00 1 January 1900 and
    054         * 00:00 1 January 1970.  This value can be useful for converting
    055         * time values to other formats.
    056         ***/
    057        public static final long SECONDS_1900_TO_1970 = 2208988800L;
    058
    059        private final byte[] __dummyData = new byte[1];
    060        private final byte[] __timeData = new byte[4];
    061
    062        /***
    063         * Retrieves the time from the specified server and port and
    064         * returns it. The time is the number of seconds since
    065         * 00:00 (midnight) 1 January 1900 GMT, as specified by RFC 868.
    066         * This method reads the raw 32-bit big-endian
    067         * unsigned integer from the server, converts it to a Java long, and
    068         * returns the value.
    069         * <p>
    070         * @param host The address of the server.
    071         * @param port The port of the service.
    072         * @return The time value retrieved from the server.
    073         * @exception IOException If an error occurs while retrieving the time.
    074         ***/
    075        public long getTime(InetAddress host, int port) throws IOException
    076        {
    077            long time;
    078            DatagramPacket sendPacket, receivePacket;
    079
    080            sendPacket =
    081                new DatagramPacket(__dummyData, __dummyData.length, host, port);
    082            receivePacket = new DatagramPacket(__timeData, __timeData.length);
    083
    084            _socket_.send(sendPacket);
    085            _socket_.receive(receivePacket);
    086
    087            time = 0L;
    088            time |= (((__timeData[0] & 0xff) << 24) & 0xffffffffL);
    089            time |= (((__timeData[1] & 0xff) << 16) & 0xffffffffL);
    090            time |= (((__timeData[2] & 0xff) << 8) & 0xffffffffL);
    091            time |= ((__timeData[3] & 0xff) & 0xffffffffL);
    092
    093            return time;
    094        }
    095
    096        /*** Same as <code> getTime(host, DEFAULT_PORT); </code> ***/
    097        public long getTime(InetAddress host) throws IOException
    098        {
    099            return getTime(host, DEFAULT_PORT);
    100        }
    101
    102
    103        /***
    104         * Retrieves the time from the server and returns a Java Date
    105         * containing the time converted to the local timezone.
    106         * <p>
    107         * @param host The address of the server.
    108         * @param port The port of the service.
    109         * @return A Date value containing the time retrieved from the server
    110         *     converted to the local timezone.
    111         * @exception IOException  If an error occurs while fetching the time.
    112         ***/
    113        public Date getDate(InetAddress host, int port) throws IOException
    114        {
    115            return new Date((getTime(host, port) - SECONDS_1900_TO_1970)*1000L);
    116        }
    117
    118
    119        /*** Same as <code> getTime(host, DEFAULT_PORT); </code> ***/
    120        public Date getDate(InetAddress host) throws IOException
    121        {
    122            return new Date((getTime(host, DEFAULT_PORT) -
    123                             SECONDS_1900_TO_1970)*1000L);
    124        }
    125
    126    }
    127