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Java > Open Source Codes > org > apache > commons > net > TimeUDPClient


1 /*
2  * Copyright 2001-2005 The Apache Software Foundation
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 package org.apache.commons.net;
17
18 import java.io.IOException JavaDoc;
19 import java.net.DatagramPacket JavaDoc;
20 import java.net.InetAddress JavaDoc;
21 import java.util.Date JavaDoc;
22
23 /***
24  * The TimeUDPClient class is a UDP implementation of a client for the
25  * Time protocol described in RFC 868. To use the class, merely
26  * open a local datagram socket with
27  * {@link org.apache.commons.net.DatagramSocketClient#open open }
28  * and call {@link #getTime getTime } or
29  * {@link #getTime getDate } to retrieve the time. Then call
30  * {@link org.apache.commons.net.DatagramSocketClient#close close }
31  * to close the connection properly. Unlike
32  * {@link org.apache.commons.net.TimeTCPClient},
33  * successive calls to {@link #getTime getTime } or
34  * {@link #getDate getDate } are permitted
35  * without re-establishing a connection. That is because UDP is a
36  * connectionless protocol and the Time protocol is stateless.
37  * <p>
38  * <p>
39  * @author Daniel F. Savarese
40  * @see TimeTCPClient
41  ***/
42
43 public final class TimeUDPClient extends DatagramSocketClient
44 {
45     /*** The default time port. It is set to 37 according to RFC 868. ***/
46     public static final int DEFAULT_PORT = 37;
47
48     /***
49      * The number of seconds between 00:00 1 January 1900 and
50      * 00:00 1 January 1970. This value can be useful for converting
51      * time values to other formats.
52      ***/
53     public static final long SECONDS_1900_TO_1970 = 2208988800L;
54
55     private byte[] __dummyData = new byte[1];
56     private byte[] __timeData = new byte[4];
57
58     /***
59      * Retrieves the time from the specified server and port and
60      * returns it. The time is the number of seconds since
61      * 00:00 (midnight) 1 January 1900 GMT, as specified by RFC 868.
62      * This method reads the raw 32-bit big-endian
63      * unsigned integer from the server, converts it to a Java long, and
64      * returns the value.
65      * <p>
66      * @param host The address of the server.
67      * @param port The port of the service.
68      * @return The time value retrieved from the server.
69      * @exception IOException If an error occurs while retrieving the time.
70      ***/
71     public long getTime(InetAddress JavaDoc host, int port) throws IOException JavaDoc
72     {
73         long time;
74         DatagramPacket JavaDoc sendPacket, receivePacket;
75
76         sendPacket =
77             new DatagramPacket JavaDoc(__dummyData, __dummyData.length, host, port);
78         receivePacket = new DatagramPacket JavaDoc(__timeData, __timeData.length);
79
80         _socket_.send(sendPacket);
81         _socket_.receive(receivePacket);
82
83         time = 0L;
84         time |= (((__timeData[0] & 0xff) << 24) & 0xffffffffL);
85         time |= (((__timeData[1] & 0xff) << 16) & 0xffffffffL);
86         time |= (((__timeData[2] & 0xff) << 8) & 0xffffffffL);
87         time |= ((__timeData[3] & 0xff) & 0xffffffffL);
88
89         return time;
90     }
91
92     /*** Same as <code> getTime(host, DEFAULT_PORT); </code> ***/
93     public long getTime(InetAddress JavaDoc host) throws IOException JavaDoc
94     {
95         return getTime(host, DEFAULT_PORT);
96     }
97
98
99     /***
100      * Retrieves the time from the server and returns a Java Date
101      * containing the time converted to the local timezone.
102      * <p>
103      * @param host The address of the server.
104      * @param port The port of the service.
105      * @return A Date value containing the time retrieved from the server
106      * converted to the local timezone.
107      * @exception IOException If an error occurs while fetching the time.
108      ***/
109     public Date JavaDoc getDate(InetAddress JavaDoc host, int port) throws IOException JavaDoc
110     {
111         return new Date JavaDoc((getTime(host, port) - SECONDS_1900_TO_1970)*1000L);
112     }
113
114
115     /*** Same as <code> getTime(host, DEFAULT_PORT); </code> ***/
116     public Date JavaDoc getDate(InetAddress JavaDoc host) throws IOException JavaDoc
117     {
118         return new Date JavaDoc((getTime(host, DEFAULT_PORT) -
119                          SECONDS_1900_TO_1970)*1000L);
120     }
121
122 }
123
124
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