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