java 通过网络 ntp 获取网络时间

需要 commons-net-3.4.jar 库。

import org.apache.commons.net.ntp.NTPUDPClient;
import org.apache.commons.net.ntp.TimeInfo;  
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.net.InetAddress.*;
import java.util.Date;
import java.util.Calendar;
import org.apache.commons.net.ntp.TimeStamp;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Locale; 
import java.io.IOException;

public class t {
    public static void main(String[] args) {  
        try {  
            NTPUDPClient timeClient = new NTPUDPClient();  
            String timeServerUrl = "24.56.178.140";  
            InetAddress timeServerAddress = InetAddress.getByName(timeServerUrl);  
            TimeInfo timeInfo = timeClient.getTime(timeServerAddress);  
            TimeStamp timeStamp = timeInfo.getMessage().getTransmitTimeStamp();  
            DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");  
            System.out.println(dateFormat.format(timeStamp.getDate()));  
        } catch (UnknownHostException e) {  
            e.printStackTrace();  
        } catch (IOException e) {  
            e.printStackTrace();  
        }  
    }  
}

npt服务器的地址大概有：

http://tf.nist.gov/tf-cgi/servers.cgi

1.cn.pool.ntp.org

2.cn.pool.ntp.org

3.cn.pool.ntp.org

0.cn.pool.ntp.org

cn.pool.ntp.org

tw.pool.ntp.org

0.tw.pool.ntp.org

1.tw.pool.ntp.org

2.tw.pool.ntp.org

3.tw.pool.ntp.org