    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     * @see TimeTCPClient
    044     ***/
    045
    046    public final class TimeUDPClient extends DatagramSocketClient
    047    {
    048        /*** The default time port.  It is set to 37 according to RFC 868. ***/
    049        public static final int DEFAULT_PORT = 37;
    050
    051        /***
    052         * The number of seconds between 00:00 1 January 1900 and
    053         * 00:00 1 January 1970.  This value can be useful for converting
    054         * time values to other formats.
    055         ***/
    056        public static final long SECONDS_1900_TO_1970 = 2208988800L;
    057
    058        private final byte[] __dummyData = new byte[1];
    059        private final byte[] __timeData = new byte[4];
    060
    061        /***
    062         * Retrieves the time from the specified server and port and
    063         * returns it. The time is the number of seconds since
    064         * 00:00 (midnight) 1 January 1900 GMT, as specified by RFC 868.
    065         * This method reads the raw 32-bit big-endian
    066         * unsigned integer from the server, converts it to a Java long, and
    067         * returns the value.
    068         * <p>
    069         * @param host The address of the server.
    070         * @param port The port of the service.
    071         * @return The time value retrieved from the server.
    072         * @exception IOException If an error occurs while retrieving the time.
    073         ***/
    074        public long getTime(InetAddress host, int port) throws IOException
    075        {
    076            long time;
    077            DatagramPacket sendPacket, receivePacket;
    078
    079            sendPacket =
    080                new DatagramPacket(__dummyData, __dummyData.length, host, port);
    081            receivePacket = new DatagramPacket(__timeData, __timeData.length);
    082
    083            _socket_.send(sendPacket);
    084            _socket_.receive(receivePacket);
    085
    086            time = 0L;
    087            time |= (((__timeData[0] & 0xff) << 24) & 0xffffffffL);
    088            time |= (((__timeData[1] & 0xff) << 16) & 0xffffffffL);
    089            time |= (((__timeData[2] & 0xff) << 8) & 0xffffffffL);
    090            time |= ((__timeData[3] & 0xff) & 0xffffffffL);
    091
    092            return time;
    093        }
    094
    095        /*** Same as <code> getTime(host, DEFAULT_PORT); </code> ***/
    096        public long getTime(InetAddress host) throws IOException
    097        {
    098            return getTime(host, DEFAULT_PORT);
    099        }
    100
    101
    102        /***
    103         * Retrieves the time from the server and returns a Java Date
    104         * containing the time converted to the local timezone.
    105         * <p>
    106         * @param host The address of the server.
    107         * @param port The port of the service.
    108         * @return A Date value containing the time retrieved from the server
    109         *     converted to the local timezone.
    110         * @exception IOException  If an error occurs while fetching the time.
    111         ***/
    112        public Date getDate(InetAddress host, int port) throws IOException
    113        {
    114            return new Date((getTime(host, port) - SECONDS_1900_TO_1970)*1000L);
    115        }
    116
    117
    118        /*** Same as <code> getTime(host, DEFAULT_PORT); </code> ***/
    119        public Date getDate(InetAddress host) throws IOException
    120        {
    121            return new Date((getTime(host, DEFAULT_PORT) -
    122                             SECONDS_1900_TO_1970)*1000L);
    123        }
    124
    125    }
    126