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    1   package examples.ntp;
    2   /*
    3    * Copyright 2001-2005 The Apache Software Foundation
    4    *
    5    * Licensed under the Apache License, Version 2.0 (the "License");
    6    * you may not use this file except in compliance with the License.
    7    * 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  import java.io.IOException;
    19  import java.net.InetAddress;
    20  import java.net.SocketException;
    21  import java.net.UnknownHostException;
    22  import java.text.NumberFormat;
    23
    24  import org.apache.commons.net.ntp.*;
    25
    26  /****
    27   * This is an example program demonstrating how to use the NTPUDPClient
    28   * class. This program sends a Datagram client request packet to a
    29   * Network time Protocol (NTP) service port on a specified server,
    30   * retrieves the time, and prints it to standard output along with
    31   * the fields from the NTP message header (e.g. stratum level, reference id,
    32   * poll interval, root delay, mode, ...)
    33   * See <A HREF="ftp://ftp.rfc-editor.org/in-notes/rfc868.txt"> the spec </A>
    34   * for details.
    35   * <p>
    36   * Usage: NTPClient <hostname-or-address-list>
    37   * <br>
    38   * Example: NTPClient clock.psu.edu
    39   *
    40   * @author Jason Mathews, MITRE Corp
    41   ***/
    42  public final class NTPClient
    43  {
    44
    45      private static final NumberFormat numberFormat = new java.text.DecimalFormat("0.00");
    46
    47      /***
    48       * Process <code>TimeInfo</code> object and print its details.
    49       * @param info <code>TimeInfo</code> object.
    50       */
    51      public static void processResponse(TimeInfo info)
    52      {
    53          NtpV3Packet message = info.getMessage();
    54          int stratum = message.getStratum();
    55          String refType;
    56          if (stratum <= 0)
    57              refType = "(Unspecified or Unavailable)";
    58          else if (stratum == 1)
    59              refType = "(Primary Reference; e.g., GPS)"; // GPS, radio clock, etc.
    60          else
    61              refType = "(Secondary Reference; e.g. via NTP or SNTP)";
    62          // stratum should be 0..15...
    63          System.out.println(" Stratum: " + stratum + " " + refType);
    64          int version = message.getVersion();
    65          int li = message.getLeapIndicator();
    66          System.out.println(" leap=" + li + ", version="
    67                  + version + ", precision=" + message.getPrecision());
    68
    69          System.out.println(" mode: " + message.getModeName() + " (" + message.getMode() + ")");
    70          int poll = message.getPoll();
    71          // poll value typically btwn MINPOLL (4) and MAXPOLL (14)
    72          System.out.println(" poll: " + (poll <= 0 ? 1 : (int) Math.pow(2, poll))
    73                  + " seconds" + " (2 ** " + poll + ")");
    74          double disp = message.getRootDispersionInMillisDouble();
    75          System.out.println(" rootdelay=" + numberFormat.format(message.getRootDelayInMillisDouble())
    76                  + ", rootdispersion(ms): " + numberFormat.format(disp));
    77
    78          int refId = message.getReferenceId();
    79          String refAddr = NtpUtils.getHostAddress(refId);
    80          String refName = null;
    81          if (refId != 0) {
    82              if (refAddr.equals("127.127.1.0")) {
    83                  refName = "LOCAL"; // This is the ref address for the Local Clock
    84              } else if (stratum >= 2) {
    85                  // If reference id has 127.127 prefix then it uses its own reference clock
    86                  // defined in the form 127.127.clock-type.unit-num (e.g. 127.127.8.0 mode 5
    87                  // for GENERIC DCF77 AM; see refclock.htm from the NTP software distribution.
    88                  if (!refAddr.startsWith("127.127")) {
    89                      try {
    90                          InetAddress addr = InetAddress.getByName(refAddr);
    91                          String name = addr.getHostName();
    92                          if (name != null && !name.equals(refAddr))
    93                              refName = name;
    94                      } catch (UnknownHostException e) {
    95                          // some stratum-2 servers sync to ref clock device but fudge stratum level higher... (e.g. 2)
    96                          // ref not valid host maybe it's a reference clock name?
    97                          // otherwise just show the ref IP address.
    98                          refName = NtpUtils.getReferenceClock(message);
    99                      }
    100                 }
    101             } else if (version >= 3 && (stratum == 0 || stratum == 1)) {
    102                 refName = NtpUtils.getReferenceClock(message);
    103                 // refname usually have at least 3 characters (e.g. GPS, WWV, LCL, etc.)
    104             }
    105             // otherwise give up on naming the beast...
    106         }
    107         if (refName != null && refName.length() > 1)
    108             refAddr += " (" + refName + ")";
    109         System.out.println(" Reference Identifier:\t" + refAddr);
    110
    111         TimeStamp refNtpTime = message.getReferenceTimeStamp();
    112         System.out.println(" Reference Timestamp:\t" + refNtpTime + "  " + refNtpTime.toDateString());
    113
    114         // Originate Time is time request sent by client (t1)
    115         TimeStamp origNtpTime = message.getOriginateTimeStamp();
    116         System.out.println(" Originate Timestamp:\t" + origNtpTime + "  " + origNtpTime.toDateString());
    117
    118         long destTime = info.getReturnTime();
    119         // Receive Time is time request received by server (t2)
    120         TimeStamp rcvNtpTime = message.getReceiveTimeStamp();
    121         System.out.println(" Receive Timestamp:\t" + rcvNtpTime + "  " + rcvNtpTime.toDateString());
    122
    123         // Transmit time is time reply sent by server (t3)
    124         TimeStamp xmitNtpTime = message.getTransmitTimeStamp();
    125         System.out.println(" Transmit Timestamp:\t" + xmitNtpTime + "  " + xmitNtpTime.toDateString());
    126
    127         // Destination time is time reply received by client (t4)
    128         TimeStamp destNtpTime = TimeStamp.getNtpTime(destTime);
    129         System.out.println(" Destination Timestamp:\t" + destNtpTime + "  " + destNtpTime.toDateString());
    130
    131         info.computeDetails(); // compute offset/delay if not already done
    132         Long offsetValue = info.getOffset();
    133         Long delayValue = info.getDelay();
    134         String delay = (delayValue == null) ? "N/A" : delayValue.toString();
    135         String offset = (offsetValue == null) ? "N/A" : offsetValue.toString();
    136
    137         System.out.println(" Roundtrip delay(ms)=" + delay
    138                 + ", clock offset(ms)=" + offset); // offset in ms
    139     }
    140
    141     public static final void main(String[] args)
    142     {
    143         if (args == null || args.length == 0) {
    144             System.err.println("Usage: NTPClient <hostname-or-address-list>");
    145             System.exit(1);
    146         }
    147
    148         NTPUDPClient client = new NTPUDPClient();
    149         // We want to timeout if a response takes longer than 10 seconds
    150         client.setDefaultTimeout(10000);
    151         try {
    152             client.open(NtpV3Packet.NTP_PORT);
    153             for (int i = 0; i < args.length; i++)
    154             {
    155                 System.out.println();
    156                 try {
    157                     InetAddress hostAddr = InetAddress.getByName(args[i]);
    158                     System.out.println("> " + hostAddr.getHostName() + "/" + hostAddr.getHostAddress());
    159                     TimeInfo info = client.getTime(hostAddr);
    160                     processResponse(info);
    161                 } catch (IOException ioe) {
    162                     ioe.printStackTrace();
    163                 }
    164             }
    165         } catch (SocketException e) {
    166             e.printStackTrace();
    167         }
    168
    169         client.close();
    170     }
    171
    172 }