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