/// <summary> /// Get time from internet server /// </summary> public static DateTime GetNetworkTime(string ntpServer = "time.windows.com") { // NTP message size - 16 bytes of the digest (RFC 2030) byte[] 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) IPAddress[] addresses = Dns.GetHostEntry(ntpServer).AddressList; //The UDP port number assigned to NTP is 123 IPEndPoint ipEndPoint = new IPEndPoint(addresses[0], 123); using (Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp)) { socket.SendTimeout = 15000; socket.ReceiveTimeout = 15000; socket.Connect(ipEndPoint); socket.Send(ntpData); socket.Receive(ntpData); } //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 = ByteTools.SwapEndianness(intPart); fractPart = ByteTools.SwapEndianness(fractPart); ulong milliseconds = (intPart * 1000) + ((fractPart * 1000) / 0x100000000L); //**UTC** time DateTime networkDateTime = (new DateTime(1900, 1, 1)).AddMilliseconds((long)milliseconds); return(networkDateTime); }