C# 获取NTP远程服务同步时间

现场有一个需要定时同步远程服务器的需求,根据一个时钟电脑，同步服务器时间，保证各个系统之间时间的一致性。

实现方法：

一、获取远程时间 

参数配置："NTPServer"  远程时间服务器地址

   public class NTPTimeHelper  {
        /// <summary>
        /// 获取NTC时间
        /// </summary>
        /// <returns></returns>
        public static DateTime GetNetworkTime()
        {

            //default Windows time server
            string ntpServer = ConfigHelper.GetConfigToStr("NTPServer", "");

            // NTP message size - 16 bytes of the digest (RFC 2030)
            var ntpData = new byte[48];

            //Setting the Leap Indicator, Version Number and Mode values
            ntpData[0] = 0x1B; //LI = 0 (no warning), VN = 3 (IPv4 only), Mode = 3 (Client Mode)

            var addresses = Dns.GetHostEntry(ntpServer).AddressList;

            //The UDP port number assigned to NTP is 123
            var ipEndPoint = new IPEndPoint(addresses[0], 123);
            //NTP uses UDP
            var socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);

            socket.Connect(ipEndPoint);

            //Stops code hang if NTP is blocked
            socket.ReceiveTimeout = 3000;

            socket.Send(ntpData);
            socket.Receive(ntpData);
            socket.Close();

            //Offset to get to the "Transmit Timestamp" field (time at which the reply 
            //departed the server for the client, in 64-bit timestamp format."
            const byte serverReplyTime = 40;

            //Get the seconds part
            ulong intPart = BitConverter.ToUInt32(ntpData, serverReplyTime);

            //Get the seconds fraction
            ulong fractPart = BitConverter.ToUInt32(ntpData, serverReplyTime + 4);

            //Convert From big-endian to little-endian
            intPart = SwapEndianness(intPart);
            fractPart = SwapEndianness(fractPart);

            var milliseconds = (intPart * 1000) + ((fractPart * 1000) / 0x100000000L);

            //**UTC** time
            var networkDateTime = (new DateTime(1900, 1, 1, 0, 0, 0, DateTimeKind.Utc)).AddMilliseconds((long)milliseconds);

            return networkDateTime.ToLocalTime();
        }

        // stackoverflow.com/a/3294698/162671
        static uint SwapEndianness(ulong x)
        {
            return (uint)(((x & 0x000000ff) << 24) +
            ((x & 0x0000ff00) << 8) +
            ((x & 0x00ff0000) >> 8) +
            ((x & 0xff000000) >> 24));
        }
    }

二、获取服务器后修改本地服务器时间：

    internal struct SYSTEMTIME
    {
        public ushort wYear;
        public ushort wMonth;
        public ushort wDayOfWeek;
        public ushort wDay;
        public ushort wHour;
        public ushort wMinute;
        public ushort wSecond;
        public ushort wMilliseconds;

        /// <summary>
        /// 从System.DateTime转换。
        /// </summary>
        /// <param name="time">System.DateTime类型的时间。</param>
        public void FromDateTime(DateTime time)
        {
            wYear = (ushort)time.Year;
            wMonth = (ushort)time.Month;
            wDayOfWeek = (ushort)time.DayOfWeek;
            wDay = (ushort)time.Day;
            wHour = (ushort)time.Hour;
            wMinute = (ushort)time.Minute;
            wSecond = (ushort)time.Second;
            wMilliseconds = (ushort)time.Millisecond;
        }
        /// <summary>
        /// 转换为System.DateTime类型。
        /// </summary>
        /// <returns></returns>
        public DateTime ToDateTime()
        {
            return new DateTime(wYear, wMonth, wDay, wHour, wMinute, wSecond, wMilliseconds);
        }
        /// <summary>
        /// 静态方法。转换为System.DateTime类型。
        /// </summary>
        /// <param name="time">SYSTEMTIME类型的时间。</param>
        /// <returns></returns>
        public static DateTime ToDateTime(SYSTEMTIME time)
        {
            return time.ToDateTime();
        }
    }
    internal class Win32API
    {
        [DllImport("Kernel32.dll")]
        public static extern bool SetLocalTime(ref SYSTEMTIME Time);
        [DllImport("Kernel32.dll")]
        public static extern void GetLocalTime(ref SYSTEMTIME Time);
    }

    public class SystemHelper
    {
        public static void SetLocalMachineTime(DateTime dt)
        {
            //转换System.DateTime到SYSTEMTIME
            SYSTEMTIME st = new SYSTEMTIME();
            st.FromDateTime(dt);
            //调用Win32 API设置系统时间
            Win32API.SetLocalTime(ref st);
        }
    }