ntp.tiny

#######################################################################
#
# Simple example of .NET socket programming with Tiny: an NTP client
# (Adapted from an MSDN C# sample).
#
#######################################################################

# The name of the NTP server to query
ntpServer = "time.windows.com"

# NTP message size - 16 bytes of the digest (RFC 2030)
ntpData = [<byte[]>].new(48)

# Setting the Leap Indicator, Version Number and Mode values
# LI = 0 (no warning), VN = 3 (IPv4 only), Mode = 3 (Client Mode)
ntpData[0] = [<byte>] 0x1b

# get the IP address of the NTP server
addresses = [<System.Net.Dns>].GetHostEntry(ntpServer).AddressList

# The UDP port number assigned to NTP is 123
ipEndPoint = [<System.Net.IPEndPoint>].new(addresses[0], 123)

# create the socket object; NTP uses UDP
socket = [<System.Net.Sockets.Socket>].new(
            [<System.Net.Sockets.AddressFamily>].InterNetwork,
            [<System.Net.Sockets.SocketType>].Dgram,
            [<System.Net.Sockets.ProtocolType>].Udp)

# Set timeout to prevent hang if NTP is blocked
socket.ReceiveTimeout = 3000

# Query the NTP server
socket.Connect(ipEndPoint)
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.
serverReplyTime = [<byte>] 40

# Get the seconds part
intPart = [<BitConverter>].ToUInt32(ntpData, serverReplyTime)

# Get the seconds fraction part
fractPart = [<BitConverter>].ToUInt32(ntpData, serverReplyTime+4)

# Utility to swap the endianness of a word
fn SwapEndianness word ->
    bor(
        bor(
            bshl(band(word, 0xff), 24),
            bshl(band(word, 0xff00), 8)),
        bor(
            bshr(band(word, 0xff0000), 8),
            bshr(band(word, 0xff000000), 24)))

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

# convert to milliseconds
milliseconds = intpart*1000 + fractPart*1000 / 0x1_0000_0000

# Compute the UTC time then add the milliseconds.
networkDateTime = [<DateTime>]
    .new(1900, 1, 1, 0, 0, 0, [<DateTimeKind>].Utc)
    .AddMilliseconds(milliseconds)

# Finally convert it to local time and return it.
networkDateTime.ToLocalTime()