C# 调用windows时间同步服务获取准确时间

1//创建一个Daytime类代码如下：using System;  
2using System.Collections;  
3using System.Collections.Generic;  
4using System.Data;  
5using System.Diagnostics;  
6using System.IO;  
7using System.Net;  
8using System.Net.Sockets;  
9using System.Runtime.InteropServices;  
10  
11public class Daytime  
12{  
13    // Internet Time Server class by Alastair Dallas 01/27/04  
14  
15    // Number of seconds  
16    private const int THRESHOLD_SECONDS = 15;  
17    // that Windows clock can deviate from NIST and still be okay  
18  
19    //Server IP addresses from   
20    //http://www.boulder.nist.gov/timefreq/service/time-servers.html  
21    private static string[] Servers = {  
22        "129.6.15.28",  
23        "129.6.15.29",  
24        "132.163.4.101",  
25        "132.163.4.102",  
26        "132.163.4.103",  
27        "128.138.140.44",  
28        "192.43.244.18",  
29        "131.107.1.10",  
30        "66.243.43.21",  
31        "216.200.93.8",  
32        "208.184.49.9",  
33        "207.126.98.204",  
34        "205.188.185.33"  
35//65.55.21.15time.windows.com微软时间同步服务器
36    };  
37    public static string LastHost = "";  
38  
39    public static DateTime LastSysTime;  
40    public static DateTime GetTime()  
41    {  
42        //Returns UTC/GMT using an NIST server if possible,   
43        // degrading to simply returning the system clock  
44  
45        //If we are successful in getting NIST time, then  
46        // LastHost indicates which server was used and  
47        // LastSysTime contains the system time of the call  
48        // If LastSysTime is not within 15 seconds of NIST time,  
49        //  the system clock may need to be reset  
50        // If LastHost is "", time is equal to system clock  
51  
52        string host = null;  
53        DateTime result = default(DateTime);  
54  
55        LastHost = "";  
56        foreach (string host_loopVariable in Servers)  
57        {  
58            host = host_loopVariable;  
59            result = GetNISTTime(host);  
60            if (result > DateTime.MinValue)  
61            {  
62                LastHost = host;  
63                break; // TODO: might not be correct. Was : Exit For  
64            }  
65        }  
66  
67        if (string.IsNullOrEmpty(LastHost))  
68        {  
69            //No server in list was successful so use system time  
70            result = DateTime.UtcNow;  
71        }  
72  
73        return result;  
74    }  
75  
76    public static int SecondsDifference(DateTime dt1, DateTime dt2)  
77    {  
78        TimeSpan span = dt1.Subtract(dt2);  
79        return span.Seconds + (span.Minutes * 60) + (span.Hours * 360);  
80    }  
81  
82    public static bool WindowsClockIncorrect()  
83    {  
84        DateTime nist = GetTime();  
85        if ((Math.Abs(SecondsDifference(nist, LastSysTime)) > THRESHOLD_SECONDS))  
86        {  
87            return true;  
88        }  
89        return false;  
90    }  
91  
92    private static DateTime GetNISTTime(string host)  
93    {  
94        //Returns DateTime.MinValue if host unreachable or does not produce time  
95        DateTime result = default(DateTime);  
96        string timeStr = null;  
97  
98        try  
99        {  
100            StreamReader reader = new StreamReader(new TcpClient(host, 13).GetStream());  
101            LastSysTime = DateTime.UtcNow;  
102            timeStr = reader.ReadToEnd();  
103            reader.Close();  
104        }  
105        catch (SocketException ex)  
106        {  
107            //Couldn't connect to server, transmission error  
108            Debug.WriteLine("Socket Exception [" + host + "]");  
109            return DateTime.MinValue;  
110        }  
111        catch (Exception ex)  
112        {  
113            //Some other error, such as Stream under/overflow  
114            return DateTime.MinValue;  
115        }  
116  
117        //Parse timeStr  
118        if ((timeStr.Substring(38, 9) != "UTC(NIST)"))  
119        {  
120            //This signature should be there  
121            return DateTime.MinValue;  
122        }  
123        if ((timeStr.Substring(30, 1) != "0"))  
124        {  
125            //Server reports non-optimum status, time off by as much as 5 seconds  
126            return DateTime.MinValue;  
127            //Try a different server  
128        }  
129  
130        int jd = int.Parse(timeStr.Substring(1, 5));  
131        int yr = int.Parse(timeStr.Substring(7, 2));  
132        int mo = int.Parse(timeStr.Substring(10, 2));  
133        int dy = int.Parse(timeStr.Substring(13, 2));  
134        int hr = int.Parse(timeStr.Substring(16, 2));  
135        int mm = int.Parse(timeStr.Substring(19, 2));  
136        int sc = int.Parse(timeStr.Substring(22, 2));  
137  
138        if ((jd < 15020))  
139        {  
140            //Date is before 1900  
141            return DateTime.MinValue;  
142        }  
143        if ((jd > 51544))  
144            yr += 2000;  
145        else  
146            yr += 1900;  
147  
148        return new DateTime(yr, mo, dy, hr, mm, sc);  
149    }  
150  
151    [StructLayout(LayoutKind.Sequential)]  
152    public struct SYSTEMTIME  
153    {  
154        public Int16 wYear;  
155        public Int16 wMonth;  
156        public Int16 wDayOfWeek;  
157        public Int16 wDay;  
158        public Int16 wHour;  
159        public Int16 wMinute;  
160        public Int16 wSecond;  
161        public Int16 wMilliseconds;  
162    }  
163    [DllImport("kernel32.dll", CharSet = CharSet.Ansi, SetLastError = true, ExactSpelling = true)]  
164    private static extern Int32 GetSystemTime(ref SYSTEMTIME stru);  
165    [DllImport("kernel32.dll", CharSet = CharSet.Ansi, SetLastError = true, ExactSpelling = true)]  
166    private static extern Int32 SetSystemTime(ref SYSTEMTIME stru);  
167  
168    public static void SetWindowsClock(DateTime dt)  
169    {  
170        //Sets system time. Note: Use UTC time; Windows will apply time zone  
171  
172        SYSTEMTIME timeStru = default(SYSTEMTIME);  
173        Int32 result = default(Int32);  
174  
175        timeStru.wYear = (Int16)dt.Year;  
176        timeStru.wMonth = (Int16)dt.Month;  
177        timeStru.wDay = (Int16)dt.Day;  
178        timeStru.wDayOfWeek = (Int16)dt.DayOfWeek;  
179        timeStru.wHour = (Int16)dt.Hour;  
180        timeStru.wMinute = (Int16)dt.Minute;  
181        timeStru.wSecond = (Int16)dt.Second;  
182        timeStru.wMilliseconds = (Int16)dt.Millisecond;  
183        result = SetSystemTime(ref timeStru);  
184    }  
185}  
186 
187
188
189调用方法：
190Daytime.GetTime().ToLocalTime()   //这个就是同步后准确的时间，DateTime类型的。