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.NTPUDPClient; 027import org.apache.commons.net.ntp.NtpUtils; 028import org.apache.commons.net.ntp.NtpV3Packet; 029import org.apache.commons.net.ntp.TimeInfo; 030import org.apache.commons.net.ntp.TimeStamp; 031 032/*** 033 * This is an example program demonstrating how to use the NTPUDPClient 034 * class. This program sends a Datagram client request packet to a 035 * Network time Protocol (NTP) service port on a specified server, 036 * retrieves the time, and prints it to standard output along with 037 * the fields from the NTP message header (e.g. stratum level, reference id, 038 * poll interval, root delay, mode, ...) 039 * See <A HREF="ftp://ftp.rfc-editor.org/in-notes/rfc868.txt"> the spec </A> 040 * for details. 041 * <p> 042 * Usage: NTPClient <hostname-or-address-list> 043 * <br> 044 * Example: NTPClient clock.psu.edu 045 * 046 ***/ 047public final class NTPClient 048{ 049 050 private static final NumberFormat numberFormat = new java.text.DecimalFormat("0.00"); 051 052 /** 053 * Process <code>TimeInfo</code> object and print its details. 054 * @param info <code>TimeInfo</code> object. 055 */ 056 public static void processResponse(TimeInfo info) 057 { 058 NtpV3Packet message = info.getMessage(); 059 int stratum = message.getStratum(); 060 String refType; 061 if (stratum <= 0) { 062 refType = "(Unspecified or Unavailable)"; 063 } else if (stratum == 1) { 064 refType = "(Primary Reference; e.g., GPS)"; // GPS, radio clock, etc. 065 } else { 066 refType = "(Secondary Reference; e.g. via NTP or SNTP)"; 067 } 068 // stratum should be 0..15... 069 System.out.println(" Stratum: " + stratum + " " + refType); 070 int version = message.getVersion(); 071 int li = message.getLeapIndicator(); 072 System.out.println(" leap=" + li + ", version=" 073 + version + ", precision=" + message.getPrecision()); 074 075 System.out.println(" mode: " + message.getModeName() + " (" + message.getMode() + ")"); 076 int poll = message.getPoll(); 077 // poll value typically btwn MINPOLL (4) and MAXPOLL (14) 078 System.out.println(" poll: " + (poll <= 0 ? 1 : (int) Math.pow(2, poll)) 079 + " seconds" + " (2 ** " + poll + ")"); 080 double disp = message.getRootDispersionInMillisDouble(); 081 System.out.println(" rootdelay=" + numberFormat.format(message.getRootDelayInMillisDouble()) 082 + ", rootdispersion(ms): " + numberFormat.format(disp)); 083 084 int refId = message.getReferenceId(); 085 String refAddr = NtpUtils.getHostAddress(refId); 086 String refName = null; 087 if (refId != 0) { 088 if (refAddr.equals("127.127.1.0")) { 089 refName = "LOCAL"; // This is the ref address for the Local Clock 090 } else if (stratum >= 2) { 091 // If reference id has 127.127 prefix then it uses its own reference clock 092 // defined in the form 127.127.clock-type.unit-num (e.g. 127.127.8.0 mode 5 093 // for GENERIC DCF77 AM; see refclock.htm from the NTP software distribution. 094 if (!refAddr.startsWith("127.127")) { 095 try { 096 InetAddress addr = InetAddress.getByName(refAddr); 097 String name = addr.getHostName(); 098 if (name != null && !name.equals(refAddr)) { 099 refName = name; 100 } 101 } catch (UnknownHostException e) { 102 // some stratum-2 servers sync to ref clock device but fudge stratum level higher... (e.g. 2) 103 // ref not valid host maybe it's a reference clock name? 104 // otherwise just show the ref IP address. 105 refName = NtpUtils.getReferenceClock(message); 106 } 107 } 108 } else if (version >= 3 && (stratum == 0 || stratum == 1)) { 109 refName = NtpUtils.getReferenceClock(message); 110 // refname usually have at least 3 characters (e.g. GPS, WWV, LCL, etc.) 111 } 112 // otherwise give up on naming the beast... 113 } 114 if (refName != null && refName.length() > 1) { 115 refAddr += " (" + refName + ")"; 116 } 117 System.out.println(" Reference Identifier:\t" + refAddr); 118 119 TimeStamp refNtpTime = message.getReferenceTimeStamp(); 120 System.out.println(" Reference Timestamp:\t" + refNtpTime + " " + refNtpTime.toDateString()); 121 122 // Originate Time is time request sent by client (t1) 123 TimeStamp origNtpTime = message.getOriginateTimeStamp(); 124 System.out.println(" Originate Timestamp:\t" + origNtpTime + " " + origNtpTime.toDateString()); 125 126 long destTime = info.getReturnTime(); 127 // Receive Time is time request received by server (t2) 128 TimeStamp rcvNtpTime = message.getReceiveTimeStamp(); 129 System.out.println(" Receive Timestamp:\t" + rcvNtpTime + " " + rcvNtpTime.toDateString()); 130 131 // Transmit time is time reply sent by server (t3) 132 TimeStamp xmitNtpTime = message.getTransmitTimeStamp(); 133 System.out.println(" Transmit Timestamp:\t" + xmitNtpTime + " " + xmitNtpTime.toDateString()); 134 135 // Destination time is time reply received by client (t4) 136 TimeStamp destNtpTime = TimeStamp.getNtpTime(destTime); 137 System.out.println(" Destination Timestamp:\t" + destNtpTime + " " + destNtpTime.toDateString()); 138 139 info.computeDetails(); // compute offset/delay if not already done 140 Long offsetValue = info.getOffset(); 141 Long delayValue = info.getDelay(); 142 String delay = (delayValue == null) ? "N/A" : delayValue.toString(); 143 String offset = (offsetValue == null) ? "N/A" : offsetValue.toString(); 144 145 System.out.println(" Roundtrip delay(ms)=" + delay 146 + ", clock offset(ms)=" + offset); // offset in ms 147 } 148 149 public static void main(String[] args) 150 { 151 if (args.length == 0) { 152 System.err.println("Usage: NTPClient <hostname-or-address-list>"); 153 System.exit(1); 154 } 155 156 NTPUDPClient client = new NTPUDPClient(); 157 // We want to timeout if a response takes longer than 10 seconds 158 client.setDefaultTimeout(10000); 159 try { 160 client.open(); 161 for (String arg : args) 162 { 163 System.out.println(); 164 try { 165 InetAddress hostAddr = InetAddress.getByName(arg); 166 System.out.println("> " + hostAddr.getHostName() + "/" + hostAddr.getHostAddress()); 167 TimeInfo info = client.getTime(hostAddr); 168 processResponse(info); 169 } catch (IOException ioe) { 170 ioe.printStackTrace(); 171 } 172 } 173 } catch (SocketException e) { 174 e.printStackTrace(); 175 } 176 177 client.close(); 178 } 179 180}