用C#获取NIST时间

嘎子 C# 2016-02-05  2,150 次浏览 Time, 时间服务 没有评论

NIST为National Institute of Standards and Technology（美国技术标准局）的缩写，他们发布了一些时间的服务，而且这些时间服务的返回格式都非常简洁，便于网络应用。

首先，在网络上找到了这个文章，http://www.360doc.com/content/10/1120/01/2482712_70833596.shtml，使用的是基于www.time.gov这个网页通过正则表达式来匹配找到时间。其实这个方法是变相的用在网页内找时间的方法，只要在能够提供时间的网站上都可以进行，也不失为一种不错的方法，但有更高效的方法。

NIST发布了很多Internet Time Service，列表在http://tf.nist.gov/tf-cgi/servers.cgi，端口为13。注意，即使是网站上公布的可用的IP也最好经过验证后使用，在国内不一定可用。在网页中输入http://131.107.13.100：13就可以得到类似于57423 16-02-05 15:14:25 00 0 0 455.0 UTC(NIST) * 这样的字符串，经过解析之后就可以得到正确的时间。

下面把自己编写的类分享给大家。

     public class TimeHelper
    {
        //Number of seconds如果系统时间和NIST的时间相差此值以上表明系统时间不正确
        private const int THRESHOLD_SECONDS = 60;

        //Server IP addresses from NIST Internet Time Servers
        private static string[] Servers = {        
        "131.107.13.100",        
        "98.175.203.200",
        "216.229.0.179",
        "128.138.141.172",
        "198.60.73.8",
        "216.228.192.69",
        "64.113.32.5",//可以使用，不稳定        
        "24.56.178.140",//可以使用，不稳定
        "time.nist.gov",
        "129.6.15.30",
        "128.138.140.44",
        };
        public static string LastHost = "";

        public static DateTime LastSysTime;

        public static DateTime GetTime(WebProxy proxy = null)
        {
            //Returns UTC/GMT using an NIST server if possible, 
            // degrading to simply returning the system clock

            //If we are successful in getting NIST time, then
            // LastHost indicates which server was used and
            // LastSysTime contains the system time of the call
            // If LastSysTime is not within 15 seconds of NIST time,
            //  the system clock may need to be reset
            // If LastHost is "", time is equal to system clock

            string host = null;
            DateTime result = default(DateTime);

            LastHost = "";
            foreach (string host_loopVariable in Servers)
            {
                host = host_loopVariable;
                result = GetNISTTime(host, proxy);
                if (result &gt; DateTime.MinValue)
                {
                    LastHost = host;
                    break; // TODO: might not be correct. Was : Exit For
                }
            }

            if (string.IsNullOrEmpty(LastHost))
            {
                //No server in list was successful so use system time
                throw new Exception("All servers is unreachable!");
                //result = DateTime.UtcNow;
            }

            return result;
        }

        public static bool WindowsClockIncorrect(WebProxy proxy = null)
        {
            DateTime nist = GetTime(proxy);
            if ((Math.Abs((nist - LastSysTime).Seconds) &gt; THRESHOLD_SECONDS))
            {
                return true;
            }
            return false;
        }

        private static DateTime GetNISTTime(string host, WebProxy proxy = null)
        {
            //Returns DateTime.MinValue if host unreachable or does not produce time
            //DateTime result = default(DateTime);
            string timeStr = null;

            try
            {
                //WebClient wc = new WebClient();
                //wc.Headers.Set(System.Net.HttpRequestHeader.UserAgent, " Mozilla/5.0 (Windows; U; Windows NT 5.2; zh-CN; rv:1.9.0.3) Gecko/2008092417 Firefox/3.0.3");
                //wc.Proxy = WebHelper.getProxy();
                
                //string uri = "http://" + host + ":13";
                //Stream stream = wc.OpenRead(uri);
                //StreamReader sr = new StreamReader(stream);
                //timeStr = sr.ReadToEnd();
                //wc.Dispose();
                //sr.Close();

                HttpWebRequest rq = (HttpWebRequest)HttpWebRequest.Create("http://" + host + ":13");
                rq.Proxy = proxy;
                rq.Method = "CONNECT";
                HttpWebResponse rp = (HttpWebResponse)rq.GetResponse();
                var st = new StreamReader(rp.GetResponseStream());
                timeStr = st.ReadToEnd();
                st.Close();
                //StreamReader reader = new StreamReader(new TcpClient(host, 13).GetStream());
                //LastSysTime = DateTime.UtcNow;
                //timeStr = reader.ReadToEnd();
                //reader.Close();
            }
            //catch (SocketException ex)
            //{
            //    //Couldn't connect to server, transmission error
            //    Debug.WriteLine("Socket Exception [" + host + "]");
            //    return DateTime.MinValue;
            //}
            catch (Exception ex)
            {
                //Some other error, such as Stream under/overflow
                return DateTime.MinValue;
            }

            //Parse timeStr
            if ((timeStr.Substring(38, 9) != "UTC(NIST)"))
            {
                //This signature should be there
                return DateTime.MinValue;
            }
            if ((timeStr.Substring(30, 1) != "0"))
            {
                //Server reports non-optimum status, time off by as much as 5 seconds
                return DateTime.MinValue;
                //Try a different server
            }

            int jd = int.Parse(timeStr.Substring(1, 5));
            int yr = int.Parse(timeStr.Substring(7, 2));
            int mo = int.Parse(timeStr.Substring(10, 2));
            int dy = int.Parse(timeStr.Substring(13, 2));
            int hr = int.Parse(timeStr.Substring(16, 2));
            int mm = int.Parse(timeStr.Substring(19, 2));
            int sc = int.Parse(timeStr.Substring(22, 2));

            if ((jd &lt; 15020))
            {
                //Date is before 1900
                return DateTime.MinValue;
            }
            if ((jd &gt; 51544))
                yr += 2000;
            else
                yr += 1900;
            return new DateTime(yr, mo, dy, hr, mm, sc);
        }
    }

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public class TimeHelper

{

//Number of seconds如果系统时间和NIST的时间相差此值以上表明系统时间不正确

private const int THRESHOLD_SECONDS = 60;

//Server IP addresses from NIST Internet Time Servers

private static string[] Servers = {

"131.107.13.100",

"98.175.203.200",

"216.229.0.179",

"128.138.141.172",

"198.60.73.8",

"216.228.192.69",

"64.113.32.5",//可以使用，不稳定

"24.56.178.140",//可以使用，不稳定

"time.nist.gov",

"129.6.15.30",

"128.138.140.44",

};

public static string LastHost = "";

public static DateTime LastSysTime;

public static DateTime GetTime(WebProxy proxy = null)

{

//Returns UTC/GMT using an NIST server if possible,

// degrading to simply returning the system clock

//If we are successful in getting NIST time, then

// LastHost indicates which server was used and

// LastSysTime contains the system time of the call

// If LastSysTime is not within 15 seconds of NIST time,

// the system clock may need to be reset

// If LastHost is "", time is equal to system clock

string host = null;

DateTime result = default(DateTime);

LastHost = "";

foreach (string host_loopVariable in Servers)

{

host = host_loopVariable;

result = GetNISTTime(host, proxy);

if (result > DateTime.MinValue)

{

LastHost = host;

break; // TODO: might not be correct. Was : Exit For

}

if (string.IsNullOrEmpty(LastHost))

{

//No server in list was successful so use system time

throw new Exception("All servers is unreachable!");

//result = DateTime.UtcNow;

}

return result;

}

public static bool WindowsClockIncorrect(WebProxy proxy = null)

{

DateTime nist = GetTime(proxy);

if ((Math.Abs((nist - LastSysTime).Seconds) > THRESHOLD_SECONDS))

{

return true;

}

return false;

}

private static DateTime GetNISTTime(string host, WebProxy proxy = null)

{

//Returns DateTime.MinValue if host unreachable or does not produce time

//DateTime result = default(DateTime);

string timeStr = null;

try

{

//WebClient wc = new WebClient();

//wc.Headers.Set(System.Net.HttpRequestHeader.UserAgent, " Mozilla/5.0 (Windows; U; Windows NT 5.2; zh-CN; rv:1.9.0.3) Gecko/2008092417 Firefox/3.0.3");

//wc.Proxy = WebHelper.getProxy();

//string uri = "http://" + host + ":13";

//Stream stream = wc.OpenRead(uri);

//StreamReader sr = new StreamReader(stream);

//timeStr = sr.ReadToEnd();

//wc.Dispose();

//sr.Close();

HttpWebRequest rq = (HttpWebRequest)HttpWebRequest.Create("http://" + host + ":13");

rq.Proxy = proxy;

rq.Method = "CONNECT";

HttpWebResponse rp = (HttpWebResponse)rq.GetResponse();

var st = new StreamReader(rp.GetResponseStream());

timeStr = st.ReadToEnd();

st.Close();

//StreamReader reader = new StreamReader(new TcpClient(host, 13).GetStream());

//LastSysTime = DateTime.UtcNow;

//timeStr = reader.ReadToEnd();

//reader.Close();

}

//catch (SocketException ex)

//{

// //Couldn't connect to server, transmission error

// Debug.WriteLine("Socket Exception [" + host + "]");

// return DateTime.MinValue;

//}

catch (Exception ex)

{

//Some other error, such as Stream under/overflow

return DateTime.MinValue;

}

//Parse timeStr

if ((timeStr.Substring(38, 9) != "UTC(NIST)"))

{

//This signature should be there

return DateTime.MinValue;

}

if ((timeStr.Substring(30, 1) != "0"))

{

//Server reports non-optimum status, time off by as much as 5 seconds

return DateTime.MinValue;

//Try a different server

}

int jd = int.Parse(timeStr.Substring(1, 5));

int yr = int.Parse(timeStr.Substring(7, 2));

int mo = int.Parse(timeStr.Substring(10, 2));

int dy = int.Parse(timeStr.Substring(13, 2));

int hr = int.Parse(timeStr.Substring(16, 2));

int mm = int.Parse(timeStr.Substring(19, 2));

int sc = int.Parse(timeStr.Substring(22, 2));

if ((jd < 15020))

{

//Date is before 1900

return DateTime.MinValue;

}

if ((jd > 51544))

yr += 2000;

else

yr += 1900;

return new DateTime(yr, mo, dy, hr, mm, sc);

}

很多注释和测试代码也没有删除，分享给大家。把源码也分享给大家：

TimeHelpers

原创文章，文章首发于：Riley Ge (@rileyge) — Steemit

原创文章，转载请注明： 转载自TsonTec:测量解决方案提供者

本文链接地址: 用C#获取NIST时间

用C#获取NIST时间

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