1 package examples.ntp;
2 /*
3 * Licensed to the Apache Software Foundation (ASF) under one or more
4 * contributor license agreements. See the NOTICE file distributed with
5 * this work for additional information regarding copyright ownership.
6 * The ASF licenses this file to You under the Apache License, Version 2.0
7 * (the "License"); you may not use this file except in compliance with
8 * the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing, software
13 * distributed under the License is distributed on an "AS IS" BASIS,
14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 * See the License for the specific language governing permissions and
16 * limitations under the License.
17 */
18
19
20 import java.io.IOException;
21 import java.net.InetAddress;
22 import java.net.SocketException;
23 import java.net.UnknownHostException;
24 import java.text.NumberFormat;
25
26 import org.apache.commons.net.ntp;
27
28 /***
29 * This is an example program demonstrating how to use the NTPUDPClient
30 * class. This program sends a Datagram client request packet to a
31 * Network time Protocol (NTP) service port on a specified server,
32 * retrieves the time, and prints it to standard output along with
33 * the fields from the NTP message header (e.g. stratum level, reference id,
34 * poll interval, root delay, mode, ...)
35 * See <A HREF="ftp://ftp.rfc-editor.org/in-notes/rfc868.txt"> the spec </A>
36 * for details.
37 * <p>
38 * Usage: NTPClient <hostname-or-address-list>
39 * <br>
40 * Example: NTPClient clock.psu.edu
41 *
42 * @author Jason Mathews, MITRE Corp
43 ***/
44 public final class NTPClient
45 {
46
47 private static final NumberFormat numberFormat = new java.text.DecimalFormat("0.00");
48
49 /**
50 * Process <code>TimeInfo</code> object and print its details.
51 * @param info <code>TimeInfo</code> object.
52 */
53 public static void processResponse(TimeInfo info)
54 {
55 NtpV3Packet message = info.getMessage();
56 int stratum = message.getStratum();
57 String refType;
58 if (stratum <= 0)
59 refType = "(Unspecified or Unavailable)";
60 else if (stratum == 1)
61 refType = "(Primary Reference; e.g., GPS)"; // GPS, radio clock, etc.
62 else
63 refType = "(Secondary Reference; e.g. via NTP or SNTP)";
64 // stratum should be 0..15...
65 System.out.println(" Stratum: " + stratum + " " + refType);
66 int version = message.getVersion();
67 int li = message.getLeapIndicator();
68 System.out.println(" leap=" + li + ", version="
69 + version + ", precision=" + message.getPrecision());
70
71 System.out.println(" mode: " + message.getModeName() + " (" + message.getMode() + ")");
72 int poll = message.getPoll();
73 // poll value typically btwn MINPOLL (4) and MAXPOLL (14)
74 System.out.println(" poll: " + (poll <= 0 ? 1 : (int) Math.pow(2, poll))
75 + " seconds" + " (2 ** " + poll + ")");
76 double disp = message.getRootDispersionInMillisDouble();
77 System.out.println(" rootdelay=" + numberFormat.format(message.getRootDelayInMillisDouble())
78 + ", rootdispersion(ms): " + numberFormat.format(disp));
79
80 int refId = message.getReferenceId();
81 String refAddr = NtpUtils.getHostAddress(refId);
82 String refName = null;
83 if (refId != 0) {
84 if (refAddr.equals("127.127.1.0")) {
85 refName = "LOCAL"; // This is the ref address for the Local Clock
86 } else if (stratum >= 2) {
87 // If reference id has 127.127 prefix then it uses its own reference clock
88 // defined in the form 127.127.clock-type.unit-num (e.g. 127.127.8.0 mode 5
89 // for GENERIC DCF77 AM; see refclock.htm from the NTP software distribution.
90 if (!refAddr.startsWith("127.127")) {
91 try {
92 InetAddress addr = InetAddress.getByName(refAddr);
93 String name = addr.getHostName();
94 if (name != null && !name.equals(refAddr))
95 refName = name;
96 } catch (UnknownHostException e) {
97 // some stratum-2 servers sync to ref clock device but fudge stratum level higher... (e.g. 2)
98 // ref not valid host maybe it's a reference clock name?
99 // otherwise just show the ref IP address.
100 refName = NtpUtils.getReferenceClock(message);
101 }
102 }
103 } else if (version >= 3 && (stratum == 0 || stratum == 1)) {
104 refName = NtpUtils.getReferenceClock(message);
105 // refname usually have at least 3 characters (e.g. GPS, WWV, LCL, etc.)
106 }
107 // otherwise give up on naming the beast...
108 }
109 if (refName != null && refName.length() > 1)
110 refAddr += " (" + refName + ")";
111 System.out.println(" Reference Identifier:\t" + refAddr);
112
113 TimeStamp refNtpTime = message.getReferenceTimeStamp();
114 System.out.println(" Reference Timestamp:\t" + refNtpTime + " " + refNtpTime.toDateString());
115
116 // Originate Time is time request sent by client (t1)
117 TimeStamp origNtpTime = message.getOriginateTimeStamp();
118 System.out.println(" Originate Timestamp:\t" + origNtpTime + " " + origNtpTime.toDateString());
119
120 long destTime = info.getReturnTime();
121 // Receive Time is time request received by server (t2)
122 TimeStamp rcvNtpTime = message.getReceiveTimeStamp();
123 System.out.println(" Receive Timestamp:\t" + rcvNtpTime + " " + rcvNtpTime.toDateString());
124
125 // Transmit time is time reply sent by server (t3)
126 TimeStamp xmitNtpTime = message.getTransmitTimeStamp();
127 System.out.println(" Transmit Timestamp:\t" + xmitNtpTime + " " + xmitNtpTime.toDateString());
128
129 // Destination time is time reply received by client (t4)
130 TimeStamp destNtpTime = TimeStamp.getNtpTime(destTime);
131 System.out.println(" Destination Timestamp:\t" + destNtpTime + " " + destNtpTime.toDateString());
132
133 info.computeDetails(); // compute offset/delay if not already done
134 Long offsetValue = info.getOffset();
135 Long delayValue = info.getDelay();
136 String delay = (delayValue == null) ? "N/A" : delayValue.toString();
137 String offset = (offsetValue == null) ? "N/A" : offsetValue.toString();
138
139 System.out.println(" Roundtrip delay(ms)=" + delay
140 + ", clock offset(ms)=" + offset); // offset in ms
141 }
142
143 public static final void main(String[] args)
144 {
145 if (args == null || args.length == 0) {
146 System.err.println("Usage: NTPClient <hostname-or-address-list>");
147 System.exit(1);
148 }
149
150 NTPUDPClient client = new NTPUDPClient();
151 // We want to timeout if a response takes longer than 10 seconds
152 client.setDefaultTimeout(10000);
153 try {
154 client.open();
155 for (int i = 0; i < args.length; i++)
156 {
157 System.out.println();
158 try {
159 InetAddress hostAddr = InetAddress.getByName(args[i]);
160 System.out.println("> " + hostAddr.getHostName() + "/" + hostAddr.getHostAddress());
161 TimeInfo info = client.getTime(hostAddr);
162 processResponse(info);
163 } catch (IOException ioe) {
164 ioe.printStackTrace();
165 }
166 }
167 } catch (SocketException e) {
168 e.printStackTrace();
169 }
170
171 client.close();
172 }
173
174 }
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