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org.apache.commons.net.ntp.NTPUDPClient |
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1 | package org.apache.commons.net.ntp; |
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2 | /* |
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3 | * Copyright 2001-2005 The Apache Software Foundation |
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4 | * |
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5 | * Licensed under the Apache License, Version 2.0 (the "License"); |
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6 | * you may not use this file except in compliance with the License. |
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7 | * You may obtain a copy of the License at |
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8 | * |
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9 | * http://www.apache.org/licenses/LICENSE-2.0 |
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10 | * |
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11 | * Unless required by applicable law or agreed to in writing, software |
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12 | * distributed under the License is distributed on an "AS IS" BASIS, |
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13 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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14 | * See the License for the specific language governing permissions and |
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15 | * limitations under the License. |
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16 | */ |
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17 | ||
18 | import java.io.IOException; |
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19 | import java.net.DatagramPacket; |
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20 | import java.net.InetAddress; |
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21 | import org.apache.commons.net.DatagramSocketClient; |
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22 | ||
23 | /*** |
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24 | * The NTPUDPClient class is a UDP implementation of a client for the |
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25 | * Network Time Protocol (NTP) described in RFC 1305 as well as the |
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26 | * Simple Network Time Protocol (SNTP) in RFC-2030. To use the class, |
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27 | * merely open a local datagram socket with <a href="#open"> open </a> |
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28 | * and call <a href="#getTime"> getTime </a> to retrieve the time. Then call |
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29 | * <a href="org.apache.commons.net.DatagramSocketClient.html#close"> close </a> |
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30 | * to close the connection properly. |
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31 | * Successive calls to <a href="#getTime"> getTime </a> are permitted |
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32 | * without re-establishing a connection. That is because UDP is a |
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33 | * connectionless protocol and the Network Time Protocol is stateless. |
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34 | * |
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35 | * @author Jason Mathews, MITRE Corp |
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36 | * @version $Revision: 165675 $ $Date: 2005-05-02 15:09:55 -0500 (Mon, 02 May 2005) $ |
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37 | ***/ |
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38 | ||
39 | 0 | public final class NTPUDPClient extends DatagramSocketClient |
40 | { |
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41 | /*** The default NTP port. It is set to 123 according to RFC 1305. ***/ |
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42 | public static final int DEFAULT_PORT = 123; |
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43 | ||
44 | 0 | private int _version = NtpV3Packet.VERSION_3; |
45 | ||
46 | /*** |
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47 | * Retrieves the time information from the specified server and port and |
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48 | * returns it. The time is the number of miliiseconds since |
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49 | * 00:00 (midnight) 1 January 1900 UTC, as specified by RFC 1305. |
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50 | * This method reads the raw NTP packet and constructs a <i>TimeInfo</i> |
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51 | * object that allows access to all the fields of the NTP message header. |
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52 | * <p> |
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53 | * @param host The address of the server. |
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54 | * @param port The port of the service. |
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55 | * @return The time value retrieved from the server. |
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56 | * @exception IOException If an error occurs while retrieving the time. |
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57 | ***/ |
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58 | public TimeInfo getTime(InetAddress host, int port) throws IOException |
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59 | { |
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60 | // if not connected then open to next available UDP port |
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61 | 0 | if (!isOpen()) |
62 | { |
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63 | 0 | open(); |
64 | } |
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65 | ||
66 | 0 | NtpV3Packet message = new NtpV3Impl(); |
67 | 0 | message.setMode(NtpV3Packet.MODE_CLIENT); |
68 | 0 | message.setVersion(_version); |
69 | 0 | DatagramPacket sendPacket = message.getDatagramPacket(); |
70 | 0 | sendPacket.setAddress(host); |
71 | 0 | sendPacket.setPort(port); |
72 | ||
73 | 0 | NtpV3Packet recMessage = new NtpV3Impl(); |
74 | 0 | DatagramPacket receivePacket = recMessage.getDatagramPacket(); |
75 | ||
76 | /* |
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77 | * Must minimize the time between getting the current time, |
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78 | * timestamping the packet, and sending it out which |
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79 | * introduces an error in the delay time. |
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80 | * No extraneous logging and initializations here !!! |
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81 | */ |
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82 | 0 | TimeStamp now = TimeStamp.getCurrentTime(); |
83 | ||
84 | // Note that if you do not set the transmit time field then originating time |
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85 | // in server response is all 0's which is "Thu Feb 07 01:28:16 EST 2036". |
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86 | 0 | message.setTransmitTime(now); |
87 | ||
88 | 0 | _socket_.send(sendPacket); |
89 | 0 | _socket_.receive(receivePacket); |
90 | ||
91 | 0 | long returnTime = System.currentTimeMillis(); |
92 | // create TimeInfo message container but don't pre-compute the details yet |
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93 | 0 | TimeInfo info = new TimeInfo(recMessage, returnTime, false); |
94 | ||
95 | 0 | return info; |
96 | } |
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97 | ||
98 | /*** |
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99 | * Retrieves the time information from the specified server on the |
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100 | * default NTP port and returns it. The time is the number of miliiseconds |
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101 | * since 00:00 (midnight) 1 January 1900 UTC, as specified by RFC 1305. |
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102 | * This method reads the raw NTP packet and constructs a <i>TimeInfo</i> |
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103 | * object that allows access to all the fields of the NTP message header. |
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104 | * <p> |
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105 | * @param host The address of the server. |
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106 | * @return The time value retrieved from the server. |
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107 | * @exception IOException If an error occurs while retrieving the time. |
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108 | ***/ |
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109 | public TimeInfo getTime(InetAddress host) throws IOException |
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110 | { |
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111 | 0 | return getTime(host, NtpV3Packet.NTP_PORT); |
112 | } |
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113 | ||
114 | /*** |
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115 | * Returns the NTP protocol version number that client sets on request packet |
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116 | * that is sent to remote host (e.g. 3=NTP v3, 4=NTP v4, etc.) |
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117 | * |
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118 | * @return the NTP protocol version number that client sets on request packet. |
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119 | * @see #setVersion(int) |
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120 | ***/ |
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121 | public int getVersion() |
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122 | { |
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123 | 0 | return _version; |
124 | } |
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125 | ||
126 | /*** |
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127 | * Sets the NTP protocol version number that client sets on request packet |
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128 | * communicate with remote host. |
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129 | * |
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130 | * @param version the NTP protocol version number |
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131 | ***/ |
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132 | public void setVersion(int version) |
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133 | { |
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134 | 0 | _version = version; |
135 | 0 | } |
136 | ||
137 | } |
This report is generated by jcoverage, Maven and Maven JCoverage Plugin. |