用C#获取NIST时间

嘎子 C# 2016-02-05  2,904 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);
        }
    }

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

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

相关主题

说点什么

分类目录

高性能服务器，就选阿里云

文章归档

广告

友情链接

用C#获取NIST时间

相关主题

说点什么

分类目录

高性能服务器，就选阿里云

标签云

文章归档

广告

友情链接