NTP测试
package examples.ntp;
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* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
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*
* http://www.apache.org/licenses/LICENSE-2.0
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import java.io.IOException;
import java.net.InetAddress;
import java.net.SocketException;
import java.net.UnknownHostException;
import java.text.NumberFormat;
import org.apache.commons.net.ntp.NTPUDPClient;
import org.apache.commons.net.ntp.NtpUtils;
import org.apache.commons.net.ntp.NtpV3Packet;
import org.apache.commons.net.ntp.TimeInfo;
import org.apache.commons.net.ntp.TimeStamp;
/***
* This is an example program demonstrating how to use the NTPUDPClient Network
* time Protocol (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. 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.
* <p>
* Usage: NTPClient <hostname-or-address-list> <br>
* Example: NTPClient clock.psu.edu
*
* @author Jason Mathews, MITRE Corp
***/
public final class NTPClient {
private static final NumberFormat numberFormat = new java.text.DecimalFormat(
"0.00");
/**
* Process <code>TimeInfo</code> object and print its details.
*
* @param info
* <code>TimeInfo</code> object.
*/
public static void processResponse(TimeInfo info) {
NtpV3Packet message = info.getMessage();
int stratum = message.getStratum();
String refType;
if (stratum <= 0)
refType = "(Unspecified or Unavailable)";
else if (stratum == 1)
refType = "(Primary Reference; e.g., GPS)"; // GPS, radio clock,
// etc.
else
refType = "(Secondary Reference; e.g. via NTP or SNTP)";
// stratum should be 0..15...
System.out.println(" Stratum: " + stratum + " " + refType);
int version = message.getVersion();
int li = message.getLeapIndicator();
System.out.println(" leap=" + li + ", version=" + version
+ ", precision=" + message.getPrecision());
System.out.println(" mode: " + message.getModeName() + " ("
+ message.getMode() + ")");
int poll = message.getPoll();
// poll value typically btwn MINPOLL (4) and MAXPOLL (14)
System.out.println(" poll: "
+ (poll <= 0 ? 1 : (int) Math.pow(2, poll)) + " seconds"
+ " (2 ** " + poll + ")");
double disp = message.getRootDispersionInMillisDouble();
System.out.println(" rootdelay="
+ numberFormat.format(message.getRootDelayInMillisDouble())
+ ", rootdispersion(ms): " + numberFormat.format(disp));
int refId = message.getReferenceId();
String refAddr = NtpUtils.getHostAddress(refId);
String refName = null;
if (refId != 0) {
if (refAddr.equals("127.127.1.0")) {
refName = "LOCAL"; // This is the ref address for the Local
// Clock
} else if (stratum >= 2) {
// If reference id has 127.127 prefix then it uses its own
// reference clock
// defined in the form 127.127.clock-type.unit-num (e.g.
// 127.127.8.0 mode 5
// for GENERIC DCF77 AM; see refclock.htm from the NTP software
// distribution.
if (!refAddr.startsWith("127.127")) {
try {
InetAddress addr = InetAddress.getByName(refAddr);
String name = addr.getHostName();
if (name != null && !name.equals(refAddr))
refName = name;
} catch (UnknownHostException e) {
// some stratum-2 servers sync to ref clock device but
// fudge stratum level higher... (e.g. 2)
// ref not valid host maybe it's a reference clock name?
// otherwise just show the ref IP address.
refName = NtpUtils.getReferenceClock(message);
}
}
} else if (version >= 3 && (stratum == 0 || stratum == 1)) {
refName = NtpUtils.getReferenceClock(message);
// refname usually have at least 3 characters (e.g. GPS, WWV,
// LCL, etc.)
}
// otherwise give up on naming the beast...
}
if (refName != null && refName.length() > 1)
refAddr += " (" + refName + ")";
System.out.println(" Reference Identifier:\t" + refAddr);
TimeStamp refNtpTime = message.getReferenceTimeStamp();
System.out.println(" Reference Timestamp:\t" + refNtpTime + " "
+ refNtpTime.toDateString());
// Originate Time is time request sent by client (t1)
TimeStamp origNtpTime = message.getOriginateTimeStamp();
System.out.println(" Originate Timestamp:\t" + origNtpTime + " "
+ origNtpTime.toDateString());
long destTime = info.getReturnTime();
// Receive Time is time request received by server (t2)
TimeStamp rcvNtpTime = message.getReceiveTimeStamp();
System.out.println(" Receive Timestamp:\t" + rcvNtpTime + " "
+ rcvNtpTime.toDateString());
// Transmit time is time reply sent by server (t3)
TimeStamp xmitNtpTime = message.getTransmitTimeStamp();
System.out.println(" Transmit Timestamp:\t" + xmitNtpTime + " "
+ xmitNtpTime.toDateString());
// Destination time is time reply received by client (t4)
TimeStamp destNtpTime = TimeStamp.getNtpTime(destTime);
System.out.println(" Destination Timestamp:\t" + destNtpTime + " "
+ destNtpTime.toDateString());
info.computeDetails(); // compute offset/delay if not already done
Long offsetValue = info.getOffset();
Long delayValue = info.getDelay();
String delay = (delayValue == null) ? "N/A" : delayValue.toString();
String offset = (offsetValue == null) ? "N/A" : offsetValue.toString();
System.out.println(" Roundtrip delay(ms)=" + delay
+ ", clock offset(ms)=" + offset); // offset in ms
}
public static final void main(String[] args) {
if (args == null || args.length == 0) {
System.err.println("Usage: NTPClient <hostname-or-address-list>");
System.exit(1);
}
NTPUDPClient client = new NTPUDPClient();
// We want to timeout if a response takes longer than 10 seconds
client.setDefaultTimeout(10000);
try {
client.open();
for (int i = 0; i < args.length; i++) {
System.out.println();
try {
InetAddress hostAddr = InetAddress.getByName(args[i]);
System.out.println("> " + hostAddr.getHostName() + "/"
+ hostAddr.getHostAddress());
TimeInfo info = client.getTime(hostAddr);
processResponse(info);
} catch (IOException ioe) {
ioe.printStackTrace();
}
}
} catch (SocketException e) {
e.printStackTrace();
}
client.close();
}
}
参数可以在下面选择一个，我测试时候用的是ntp.nasa.gov，
测试结果：
> ntp.nasa.gov/198.123.30.132
Stratum: 1 (Primary Reference; e.g., GPS)
leap=0, version=3, precision=-16
mode: Server (4)
poll: 8 seconds (2 ** 3)
rootdelay=0.00, rootdispersion(ms): 0.85
Reference Identifier: 71.80.83.0 (GPS)
Reference Timestamp: d0e3a8ae.7dee6367 Fri, Jan 21 2011 14:39:42.492
Originate Timestamp: d0e3a851.9ced9168 Fri, Jan 21 2011 14:38:09.613
Receive Timestamp: d0e3a8c6.485327f3 Fri, Jan 21 2011 14:40:06.283
Transmit Timestamp: d0e3a8c6.4856fb74 Fri, Jan 21 2011 14:40:06.283
Destination Timestamp: d0e3a852.16041893 Fri, Jan 21 2011 14:38:10.086
Roundtrip delay(ms)=473, clock offset(ms)=116433
附注1：中国大概能用的NTP时间服务器
server 133.100.11.8 prefer
server 210.72.145.44
server 203.117.180.36 //程序中所用的
server 131.107.1.10
server time.asia.apple.com
server 64.236.96.53
server 130.149.17.21
server 66.92.68.246
server www.freebsd.org
server 18.145.0.30
server clock.via.net
server 137.92.140.80
server 133.100.9.2
server 128.118.46.3
server ntp.nasa.gov
server 129.7.1.66
server ntp-sop.inria.frserver 210.72.145.44(国家授时中心服务器IP地址)
ntpdate 131.107.1.10
ntpdate -s time.asia.apple.com
附注2：NTP概念简介
Network Time Protocol（NTP）是用来使计算机时间同步化的一种协议，它可以使计算机对其服务器或时钟源（如石英钟，GPS等等)做同步化，它可以提供高精准 度的时间校正（LAN上与标准间差小于1毫秒，WAN上几十毫秒），且可介由加密确认的方式来防止恶毒的协议攻击。
部分参考自：