001package examples.ntp;
002/*
003 * Licensed to the Apache Software Foundation (ASF) under one or more
004 * contributor license agreements.  See the NOTICE file distributed with
005 * this work for additional information regarding copyright ownership.
006 * The ASF licenses this file to You under the Apache License, Version 2.0
007 * (the "License"); you may not use this file except in compliance with
008 * the License.  You may obtain a copy of the License at
009 *
010 *      http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019
020import java.io.IOException;
021import java.net.InetAddress;
022import java.net.SocketException;
023import java.net.UnknownHostException;
024import java.text.NumberFormat;
025
026import org.apache.commons.net.ntp.*;
027
028/***
029 * This is an example program demonstrating how to use the NTPUDPClient
030 * class. This program sends a Datagram client request packet to a
031 * Network time Protocol (NTP) service port on a specified server,
032 * retrieves the time, and prints it to standard output along with
033 * the fields from the NTP message header (e.g. stratum level, reference id,
034 * poll interval, root delay, mode, ...)
035 * See <A HREF="ftp://ftp.rfc-editor.org/in-notes/rfc868.txt"> the spec </A>
036 * for details.
037 * <p>
038 * Usage: NTPClient <hostname-or-address-list>
039 * <br>
040 * Example: NTPClient clock.psu.edu
041 *
042 * @author Jason Mathews, MITRE Corp
043 ***/
044public final class NTPClient
045{
046
047    private static final NumberFormat numberFormat = new java.text.DecimalFormat("0.00");
048
049    /**
050     * Process <code>TimeInfo</code> object and print its details.
051     * @param info <code>TimeInfo</code> object.
052     */
053    public static void processResponse(TimeInfo info)
054    {
055        NtpV3Packet message = info.getMessage();
056        int stratum = message.getStratum();
057        String refType;
058        if (stratum <= 0)
059            refType = "(Unspecified or Unavailable)";
060        else if (stratum == 1)
061            refType = "(Primary Reference; e.g., GPS)"; // GPS, radio clock, etc.
062        else
063            refType = "(Secondary Reference; e.g. via NTP or SNTP)";
064        // stratum should be 0..15...
065        System.out.println(" Stratum: " + stratum + " " + refType);
066        int version = message.getVersion();
067        int li = message.getLeapIndicator();
068        System.out.println(" leap=" + li + ", version="
069                + version + ", precision=" + message.getPrecision());
070
071        System.out.println(" mode: " + message.getModeName() + " (" + message.getMode() + ")");
072        int poll = message.getPoll();
073        // poll value typically btwn MINPOLL (4) and MAXPOLL (14)
074        System.out.println(" poll: " + (poll <= 0 ? 1 : (int) Math.pow(2, poll))
075                + " seconds" + " (2 ** " + poll + ")");
076        double disp = message.getRootDispersionInMillisDouble();
077        System.out.println(" rootdelay=" + numberFormat.format(message.getRootDelayInMillisDouble())
078                + ", rootdispersion(ms): " + numberFormat.format(disp));
079
080        int refId = message.getReferenceId();
081        String refAddr = NtpUtils.getHostAddress(refId);
082        String refName = null;
083        if (refId != 0) {
084            if (refAddr.equals("127.127.1.0")) {
085                refName = "LOCAL"; // This is the ref address for the Local Clock
086            } else if (stratum >= 2) {
087                // If reference id has 127.127 prefix then it uses its own reference clock
088                // defined in the form 127.127.clock-type.unit-num (e.g. 127.127.8.0 mode 5
089                // for GENERIC DCF77 AM; see refclock.htm from the NTP software distribution.
090                if (!refAddr.startsWith("127.127")) {
091                    try {
092                        InetAddress addr = InetAddress.getByName(refAddr);
093                        String name = addr.getHostName();
094                        if (name != null && !name.equals(refAddr))
095                            refName = name;
096                    } catch (UnknownHostException e) {
097                        // some stratum-2 servers sync to ref clock device but fudge stratum level higher... (e.g. 2)
098                        // ref not valid host maybe it's a reference clock name?
099                        // 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}