/// <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);
}