通過TCP形式來獲取NTP時間。主要代碼如下：

 [DllImport("kernel32.dll")]
        private static extern bool SetLocalTime(ref Systemtime time);

        [StructLayout(LayoutKind.Sequential)]
        private struct Systemtime
        {
            public short year;
            public short month;
            public short dayOfWeek;
            public short day;
            public short hour;
            public short minute;
            public short second;
            public short milliseconds;
        }

        /// <summary>
        /// 設置系統時間
        /// </summary>
        /// <param name="dt">需要設置的時間</param>
        /// <returns>返回系統時間設置狀態，true為成功，false為失敗</returns>
        public static bool SetLocalDateTime(DateTime dt)
        {
            Systemtime st;

            st.year = (short)dt.Year;
            st.month = (short)dt.Month;
            st.dayOfWeek = (short)dt.DayOfWeek;
            st.day = (short)dt.Day;
            st.hour = (short)dt.Hour;
            st.minute = (short)dt.Minute;
            st.second = (short)dt.Second;
            st.milliseconds = (short)dt.Millisecond;
            bool rt = SetLocalTime(ref st);
            return rt;
        }


        public static DateTime GetDateTime(long timeStamp)
        {
            return new DateTime(1970, 1, 1).AddSeconds(timeStamp).ToLocalTime();
        }

        public static bool GetInternetTime(string url, out DateTime dt, out string errMsg)
        {
            dt = DateTime.MinValue;
            var startDt = DateTime.Now;
            var port = 13;
            var socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp) { ReceiveTimeout = 2000 };
            try
            {
                var iphostinfo = Dns.GetHostEntry(url);
                var ip = iphostinfo.AddressList[0];
                var ipe = new IPEndPoint(ip, port);

                var iar = socket.BeginConnect(ipe, null, null);
                if (!iar.AsyncWaitHandle.WaitOne(5000))
                {
                    errMsg = "連接超時" + url;
                    return false;
                }
                var recvBuffer = new byte[1024];
                var sb = new StringBuilder();
                var myE = Encoding.UTF8;

                int nBytes;
                while ((nBytes = socket.Receive(recvBuffer, 0, 1024, SocketFlags.None)) > 0)
                {
                    sb.Append(myE.GetString(recvBuffer, 0, nBytes));
                }
                var o = sb.ToString().Split(‘ ‘);


                TimeSpan ts = DateTime.Now - startDt;

                var setDt = Convert.ToDateTime(o[1] + " " + o[2]).Subtract(-ts); // 減去中途消耗的時間


                dt = setDt.ToLocalTime();
                Console.WriteLine(@"服務器：{0}時間：{1}", url, setDt);
                errMsg = "";
                return true;
            }
            catch (Exception ex)
            {

                errMsg = ex.Message;
                return false;
            }
            finally
            {
                socket.Close();
            }
        }

源碼如下：

https://files.cnblogs.com/files/lizhijian/%E8%8E%B7%E5%8F%96%E7%BD%91%E7%BB%9C%E6%97%B6%E9%97%B4.rar

感謝閱讀

c#獲取網絡時間並同步本地時間