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