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    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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