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
18 package org.apache.commons.net.time;
19
20 import java.io.IOException;
21 import java.net.DatagramPacket;
22 import java.net.InetAddress;
23 import java.util.Date;
24
25 import org.apache.commons.net.DatagramSocketClient;
26
27 /**
28 * The TimeUDPClient class is a UDP implementation of a client for the Time protocol described in RFC 868. To use the class, merely open a local datagram socket
29 * with {@link org.apache.commons.net.DatagramSocketClient#open open } and call {@link #getTime getTime } or {@link #getTime getDate } to retrieve the time.
30 * Then call {@link org.apache.commons.net.DatagramSocketClient#close close } to close the connection properly. Unlike
31 * {@link org.apache.commons.net.time.TimeTCPClient}, successive calls to {@link #getTime getTime } or {@link #getDate getDate } are permitted without
32 * re-establishing a connection. That is because UDP is a connectionless protocol and the Time protocol is stateless.
33 *
34 *
35 * @see TimeTCPClient
36 */
37
38 public final class TimeUDPClient extends DatagramSocketClient {
39 /** The default time port. It is set to 37 according to RFC 868. */
40 public static final int DEFAULT_PORT = 37;
41
42 /**
43 * The number of seconds between 00:00 1 January 1900 and 00:00 1 January 1970. This value can be useful for converting time values to other formats.
44 */
45 public static final long SECONDS_1900_TO_1970 = 2208988800L;
46
47 private final byte[] dummyData = new byte[1];
48 private final byte[] timeData = new byte[4];
49
50 /**
51 * Same as <code> getTime(host, DEFAULT_PORT); </code>
52 *
53 * @param host the time-server
54 * @return the date
55 * @throws IOException on error
56 */
57 public Date getDate(final InetAddress host) throws IOException {
58 return new Date((getTime(host, DEFAULT_PORT) - SECONDS_1900_TO_1970) * 1000L);
59 }
60
61 /**
62 * Retrieves the time from the server and returns a Java Date containing the time converted to the local time zone.
63 *
64 * @param host The address of the server.
65 * @param port The port of the service.
66 * @return A Date value containing the time retrieved from the server converted to the local time zone.
67 * @throws IOException If an error occurs while fetching the time.
68 */
69 public Date getDate(final InetAddress host, final int port) throws IOException {
70 return new Date((getTime(host, port) - SECONDS_1900_TO_1970) * 1000L);
71 }
72
73 /**
74 * Same as <code> getTime(host, DEFAULT_PORT); </code>
75 *
76 * @param host the time-server
77 * @return the time returned from the server
78 * @throws IOException on error
79 */
80 public long getTime(final InetAddress host) throws IOException {
81 return getTime(host, DEFAULT_PORT);
82 }
83
84 /**
85 * Retrieves the time from the specified server and port and returns it. The time is the number of seconds since 00:00 (midnight) 1 January 1900 GMT, as
86 * specified by RFC 868. This method reads the raw 32-bit big-endian unsigned integer from the server, converts it to a Java long, and returns the value.
87 *
88 * @param host The address of the server.
89 * @param port The port of the service.
90 * @return The time value retrieved from the server.
91 * @throws IOException If an error occurs while retrieving the time.
92 */
93 public long getTime(final InetAddress host, final int port) throws IOException {
94 final DatagramPacket sendPacket = new DatagramPacket(dummyData, dummyData.length, host, port);
95 final DatagramPacket receivePacket = new DatagramPacket(timeData, timeData.length);
96
97 checkOpen().send(sendPacket);
98 checkOpen().receive(receivePacket);
99
100 long time = 0L;
101 time |= (timeData[0] & 0xff) << 24 & 0xffffffffL;
102 time |= (timeData[1] & 0xff) << 16 & 0xffffffffL;
103 time |= (timeData[2] & 0xff) << 8 & 0xffffffffL;
104 time |= timeData[3] & 0xff & 0xffffffffL;
105
106 return time;
107 }
108
109 }