如何使用C#从互联网或服务器获取当前日期和时间？我正在努力争取时间如下：
public static DateTime GetNetworkTime (string ntpServer)
{
IPAddress[] address = Dns.GetHostEntry(ntpServer).AddressList;
if (address == null || address.Length == 0)
throw new ArgumentException("Could not resolve ip address from '" + ntpServer + "'.", "ntpServer");
IPEndPoint ep = new IPEndPoint(address[0], 123);
return GetNetworkTime(ep);
}
我将服务器IP地址作为netServer传递，但它无法正常工作。
以下是可用于从NIST互联网时间服务检索时间的代码示例
var client = new TcpClient("time.nist.gov", 13);
using (var streamReader = new StreamReader(client.GetStream()))
{
var response = streamReader.ReadToEnd();
var utcDateTimeString = response.Substring(7, 17);
var localDateTime = DateTime.ParseExact(utcDateTimeString, "yy-MM-dd HH:mm:ss", CultureInfo.InvariantCulture, DateTimeStyles.AssumeUniversal);
}
这里有一个快速代码，可以从标头中获取时间，无需端口13 即可工作
public static DateTime GetNistTime()
{
var myHttpWebRequest = (HttpWebRequest)WebRequest.Create("http://www.microsoft.com");
var response = myHttpWebRequest.GetResponse();
string todaysDates = response.Headers["date"];
return DateTime.ParseExact(todaysDates,
"ddd, dd MMM yyyy HH:mm:ss 'GMT'",
CultureInfo.InvariantCulture.DateTimeFormat,
DateTimeStyles.AssumeUniversal);
}
事情可能会出错。上面建立的代码的所有实现都容易出错。有时，它会工作，有时它会发出WebExpection错误消息。
更好的实现：
try{
using (var response =
WebRequest.Create("http://www.google.com").GetResponse())
//string todaysDates = response.Headers["date"];
return DateTime.ParseExact(response.Headers["date"],
"ddd, dd MMM yyyy HH:mm:ss 'GMT'",
CultureInfo.InvariantCulture.DateTimeFormat,
DateTimeStyles.AssumeUniversal);
}
catch (WebException)
{
return DateTime.Now; //In case something goes wrong.
}
结论：
让你的网络应用程序依赖于提供准确日期信息的服务至关重要。我在我的应用程序中使用了其中一个代码，它真的把事情搞砸了。
同样想法的另一个版本：
public static class InternetTime
{
public static DateTimeOffset? GetCurrentTime()
{
using (var client = new HttpClient())
{
try
{
var result = client.GetAsync("https://google.com",
HttpCompletionOption.ResponseHeadersRead).Result;
return result.Headers.Date;
}
catch
{
return null;
}
}
}
}
这里HttpCompletionOption.ResponseHeadersRead用于防止加载其余的响应，因为我们只需要HTTP头。
使用InternetTime.GetCurrentTime().Value.ToLocalTime()获取当前本地时间。
重要：首先检查上的可用服务器NIST互联网时间服务器。
public static DateTime GetServerTime()
{
var result = DateTime.Now;
// Initialize the list of NIST time servers
// http://tf.nist.gov/tf-cgi/servers.cgi
string[] servers = new string[] {
"time-c.nist.gov",
"time-d.nist.gov",
"nist1-macon.macon.ga.us",
"wolfnisttime.com",
"nist.netservicesgroup.com",
"nisttime.carsoncity.k12.mi.us",
"nist1-lnk.binary.net",
"wwv.nist.gov",
"time.nist.gov",
"utcnist.colorado.edu",
"utcnist2.colorado.edu",
"nist-time-server.eoni.com",
"nist-time-server.eoni.com"
};
Random rnd = new Random();
foreach (string server in servers.OrderBy(x => rnd.NextDouble()).Take(9))
{
try
{
// Connect to the server (at port 13) and get the response. Timeout max 1second
string serverResponse = string.Empty;
var tcpClient = new TcpClient();
if (tcpClient.ConnectAsync(server, 13).Wait(1000))
{
using (var reader = new StreamReader(tcpClient.GetStream()))
{
serverResponse = reader.ReadToEnd();
}
}
// If a response was received
if (!string.IsNullOrEmpty(serverResponse))
{
// Split the response string ("55596 11-02-14 13:54:11 00 0 0 478.1 UTC(NIST) *")
string[] tokens = serverResponse.Split(' ');
// Check the number of tokens
if (tokens.Length >= 6)
{
// Check the health status
string health = tokens[5];
if (health == "0")
{
// Get date and time parts from the server response
string[] dateParts = tokens[1].Split('-');
string[] timeParts = tokens[2].Split(':');
// Create a DateTime instance
DateTime utcDateTime = new DateTime(
Convert.ToInt32(dateParts[0]) + 2000,
Convert.ToInt32(dateParts[1]), Convert.ToInt32(dateParts[2]),
Convert.ToInt32(timeParts[0]), Convert.ToInt32(timeParts[1]),
Convert.ToInt32(timeParts[2]));
// Convert received (UTC) DateTime value to the local timezone
result = utcDateTime.ToLocalTime();
return result;
// Response successfully received; exit the loop
}
}
}
}
catch
{
// Ignore exception and try the next server
}
}
return result;
}
public static Nullable<DateTime> GetDateTime()
{
Nullable<DateTime> dateTime = null;
System.Net.HttpWebRequest request = (System.Net.HttpWebRequest)System.Net.WebRequest.Create("http://www.microsoft.com");
request.Method = "GET";
request.Accept = "text/html, application/xhtml+xml, */*";
request.UserAgent = "Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; Trident/6.0)";
request.ContentType = "application/x-www-form-urlencoded";
request.CachePolicy = new System.Net.Cache.RequestCachePolicy(System.Net.Cache.RequestCacheLevel.NoCacheNoStore);
try
{
System.Net.HttpWebResponse response = (System.Net.HttpWebResponse)request.GetResponse();
if (response.StatusCode == System.Net.HttpStatusCode.OK)
{
string todaysDates = response.Headers["date"];
dateTime = DateTime.ParseExact(todaysDates, "ddd, dd MMM yyyy HH:mm:ss 'GMT'",
System.Globalization.CultureInfo.InvariantCulture.DateTimeFormat, System.Globalization.DateTimeStyles.AssumeUniversal);
}
}
catch
{
dateTime = null;
}
return dateTime;
}