Java代码获取NTP服务器时间

https://my.oschina.net/rupertwong/blog/538913

apache的commons-net包下面有ntp相关的实现类，主要类有：

 org.apache.commons.net.ntp.NTPUDPClient

 org.apache.commons.net.ntp.TimeInfo

类NTPUDPClient中相关方法:

 TimeInfo getTime(InetAddress host, int port) throws IOException

TimeInfo getTime(InetAddress host) throws IOException

其中，第二个重载方法使用协议规范默认端口：123。

Java代码段：

1. public static void main(String[] args) throws IOException {

2. try {

3. NTPUDPClient timeClient = new NTPUDPClient();

4. String timeServerUrl = "202.120.2.101";

5. InetAddress timeServerAddress = InetAddress.getByName(timeServerUrl);

6. TimeInfo timeInfo = timeClient.getTime(timeServerAddress);

7. TimeStamp timeStamp = timeInfo.getMessage().getTransmitTimeStamp();

8. Date date = timeStamp.getDate();

9. System.out.println(date);

10. DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");

11. System.out.println(dateFormat.format(date));

12. } catch (UnknownHostException e) {

13. e.printStackTrace();

14. }

15. }

运行结果为：

1. Thu Dec 03 16:16:50 CST 2015

2. 2015-12-03 04:16:50

附：常用速度较快NTP服务器地址：

ntp.sjtu.edu.cn 202.120.2.101 (上海交通大学网络中心NTP服务器地址）

time-a.nist.gov 129.6.15.28 NIST, Gaithersburg, Maryland

time-b.nist.gov 129.6.15.29 NIST, Gaithersburg, Maryland

time-a.timefreq.bldrdoc.gov 132.163.4.101 NIST, Boulder, Colorado

time-b.timefreq.bldrdoc.gov 132.163.4.102 NIST, Boulder, Colorado

time-c.timefreq.bldrdoc.gov 132.163.4.103 NIST, Boulder, Colorado