001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 018package org.apache.commons.net.examples.ntp; 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 class. This program sends a Datagram client request packet to a Network time Protocol 034 * (NTP) service port on a specified server, retrieves the time, and prints it to standard output along with the fields from the NTP message header (e.g. 035 * stratum level, reference id, poll interval, root delay, mode, ...) See <A HREF="ftp://ftp.rfc-editor.org/in-notes/rfc868.txt"> the spec </A> for details. 036 * <p> 037 * Usage: NTPClient <hostname-or-address-list> 038 * </p> 039 * <p> 040 * Example: NTPClient clock.psu.edu 041 * </p> 042 */ 043public final class NTPClient { 044 045 private static final NumberFormat numberFormat = new java.text.DecimalFormat("0.00"); 046 047 public static void main(final String[] args) { 048 if (args.length == 0) { 049 System.err.println("Usage: NTPClient <hostname-or-address-list>"); 050 System.exit(1); 051 } 052 053 final NTPUDPClient client = new NTPUDPClient(); 054 // We want to timeout if a response takes longer than 10 seconds 055 client.setDefaultTimeout(10000); 056 try { 057 client.open(); 058 for (final String arg : args) { 059 System.out.println(); 060 try { 061 final InetAddress hostAddr = InetAddress.getByName(arg); 062 System.out.println("> " + hostAddr.getHostName() + "/" + hostAddr.getHostAddress()); 063 final TimeInfo info = client.getTime(hostAddr); 064 processResponse(info); 065 } catch (final IOException ioe) { 066 ioe.printStackTrace(); 067 } 068 } 069 } catch (final SocketException e) { 070 e.printStackTrace(); 071 } 072 073 client.close(); 074 } 075 076 /** 077 * Process <code>TimeInfo</code> object and print its details. 078 * 079 * @param info <code>TimeInfo</code> object. 080 */ 081 public static void processResponse(final TimeInfo info) { 082 final NtpV3Packet message = info.getMessage(); 083 final int stratum = message.getStratum(); 084 final String refType; 085 if (stratum <= 0) { 086 refType = "(Unspecified or Unavailable)"; 087 } else if (stratum == 1) { 088 refType = "(Primary Reference; e.g., GPS)"; // GPS, radio clock, etc. 089 } else { 090 refType = "(Secondary Reference; e.g. via NTP or SNTP)"; 091 } 092 // stratum should be 0..15... 093 System.out.println(" Stratum: " + stratum + " " + refType); 094 final int version = message.getVersion(); 095 final int li = message.getLeapIndicator(); 096 System.out.println(" leap=" + li + ", version=" + version + ", precision=" + message.getPrecision()); 097 098 System.out.println(" mode: " + message.getModeName() + " (" + message.getMode() + ")"); 099 final int poll = message.getPoll(); 100 // poll value typically btwn MINPOLL (4) and MAXPOLL (14) 101 System.out.println(" poll: " + (poll <= 0 ? 1 : (int) Math.pow(2, poll)) + " seconds" + " (2 ** " + poll + ")"); 102 final double disp = message.getRootDispersionInMillisDouble(); 103 System.out.println(" rootdelay=" + numberFormat.format(message.getRootDelayInMillisDouble()) + ", rootdispersion(ms): " + numberFormat.format(disp)); 104 105 final int refId = message.getReferenceId(); 106 String refAddr = NtpUtils.getHostAddress(refId); 107 String refName = null; 108 if (refId != 0) { 109 if (refAddr.equals("127.127.1.0")) { 110 refName = "LOCAL"; // This is the ref address for the Local Clock 111 } else if (stratum >= 2) { 112 // If reference id has 127.127 prefix then it uses its own reference clock 113 // defined in the form 127.127.clock-type.unit-num (e.g. 127.127.8.0 mode 5 114 // for GENERIC DCF77 AM; see refclock.htm from the NTP software distribution. 115 if (!refAddr.startsWith("127.127")) { 116 try { 117 final InetAddress addr = InetAddress.getByName(refAddr); 118 final String name = addr.getHostName(); 119 if (name != null && !name.equals(refAddr)) { 120 refName = name; 121 } 122 } catch (final UnknownHostException e) { 123 // some stratum-2 servers sync to ref clock device but fudge stratum level higher... (e.g. 2) 124 // ref not valid host maybe it's a reference clock name? 125 // otherwise just show the ref IP address. 126 refName = NtpUtils.getReferenceClock(message); 127 } 128 } 129 } else if (version >= 3 && (stratum == 0 || stratum == 1)) { 130 refName = NtpUtils.getReferenceClock(message); 131 // refname usually have at least 3 characters (e.g. GPS, WWV, LCL, etc.) 132 } 133 // otherwise give up on naming the beast... 134 } 135 if (refName != null && refName.length() > 1) { 136 refAddr += " (" + refName + ")"; 137 } 138 System.out.println(" Reference Identifier:\t" + refAddr); 139 140 final TimeStamp refNtpTime = message.getReferenceTimeStamp(); 141 System.out.println(" Reference Timestamp:\t" + refNtpTime + " " + refNtpTime.toDateString()); 142 143 // Originate Time is time request sent by client (t1) 144 final TimeStamp origNtpTime = message.getOriginateTimeStamp(); 145 System.out.println(" Originate Timestamp:\t" + origNtpTime + " " + origNtpTime.toDateString()); 146 147 final long destTimeMillis = info.getReturnTime(); 148 // Receive Time is time request received by server (t2) 149 final TimeStamp rcvNtpTime = message.getReceiveTimeStamp(); 150 System.out.println(" Receive Timestamp:\t" + rcvNtpTime + " " + rcvNtpTime.toDateString()); 151 152 // Transmit time is time reply sent by server (t3) 153 final TimeStamp xmitNtpTime = message.getTransmitTimeStamp(); 154 System.out.println(" Transmit Timestamp:\t" + xmitNtpTime + " " + xmitNtpTime.toDateString()); 155 156 // Destination time is time reply received by client (t4) 157 final TimeStamp destNtpTime = TimeStamp.getNtpTime(destTimeMillis); 158 System.out.println(" Destination Timestamp:\t" + destNtpTime + " " + destNtpTime.toDateString()); 159 160 info.computeDetails(); // compute offset/delay if not already done 161 final Long offsetMillis = info.getOffset(); 162 final Long delayMillis = info.getDelay(); 163 final String delay = delayMillis == null ? "N/A" : delayMillis.toString(); 164 final String offset = offsetMillis == null ? "N/A" : offsetMillis.toString(); 165 166 System.out.println(" Roundtrip delay(ms)=" + delay + ", clock offset(ms)=" + offset); // offset in ms 167 } 168 169}