Imports System
Imports System.Net
Imports System.Net.Sockets
Imports System.Runtime.InteropServices
Imports System.Text
Namespace InternetTime
'Leap indicator field values
Public Enum _LeapIndicator
NoWarning '0 - No warning
LastMinute61 '1 - Last minute has 61 seconds
LastMinute59 '2 - Last minute has 59 seconds
Alarm '3 - Alarm condition (clock not synchronized)
End Enum
'Mode field values
Public Enum _Mode
SymmetricActive '1 - Symmetric active
SymmetricPassive '2 - Symmetric pasive
Client '3 - Client
Server '4 - Server
Broadcast '5 - Broadcast
Unknown '0, 6, 7 - Reserved
End Enum
'Stratum field values
Public Enum _Stratum
Unspecified '0 - unspecified or unavailable
PrimaryReference '1 - primary reference (e.g. radio-clock)
SecondaryReference '2-15 - secondary reference (via NTP or SNTP)
Reserved '16-255 - reserved
End Enum
'///
'/// SNTPClient is a VB.NET# class designed to connect to time servers on the Internet and
'/// fetch the current date and time. Optionally, it may update the time of the local system.
'/// The implementation of the protocol is based on the RFC 2030.
'///
'/// Public class members:
'///
'/// LeapIndicator - Warns of an impending leap second to be inserted/deleted in the last
'/// minute of the current day. (See the _LeapIndicator enum)
'///
'/// VersionNumber - Version number of the protocol (3 or 4).
'///
'/// Mode - Returns mode. (See the _Mode enum)
'///
'/// Stratum - Stratum of the clock. (See the _Stratum enum)
'///
'/// PollInterval - Maximum interval between successive messages
'///
'/// Precision - Precision of the clock
'///
'/// RootDelay - Round trip time to the primary reference source.
'///
'/// RootDispersion - Nominal error relative to the primary reference source.
'///
'/// ReferenceID - Reference identifier (either a 4 character string or an IP address).
'///
'/// ReferenceTimestamp - The time at which the clock was last set or corrected.
'///
'/// OriginateTimestamp - The time at which the request departed the client for the server.
'///
'/// ReceiveTimestamp - The time at which the request arrived at the server.
'///
'/// Transmit Timestamp - The time at which the reply departed the server for client.
'///
'/// RoundTripDelay - The time between the departure of request and arrival of reply.
'///
'/// LocalClockOffset - The offset of the local clock relative to the primary reference
'/// source.
'///
'/// Initialize - Sets up data structure and prepares for connection.
'///
'/// Connect - Connects to the time server and populates the data structure.
'/// It can also update the system time.
'///
'/// IsResponseValid - Returns true if received data is valid and if comes from
'/// a NTP-compliant time server.
'///
'/// ToString - Returns a string representation of the object.
'///
'/// -----------------------------------------------------------------------------
'/// Structure of the standard NTP header (as described in RFC 2030)
'/// 1 2 3
'/// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
'/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
'/// |LI | VN |Mode | Stratum | Poll | Precision |
'/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
'/// | Root Delay |
'/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
'/// | Root Dispersion |
'/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
'/// | Reference Identifier |
'/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
'/// | |
'/// | Reference Timestamp (64) |
'/// | |
'/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
'/// | |
'/// | Originate Timestamp (64) |
'/// | |
'/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
'/// | |
'/// | Receive Timestamp (64) |
'/// | |
'/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
'/// | |
'/// | Transmit Timestamp (64) |
'/// | |
'/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
'/// | Key Identifier (optional) (32) |
'/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
'/// | |
'/// | |
'/// | Message Digest (optional) (128) |
'/// | |
'/// | |
'/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
'///
'/// -----------------------------------------------------------------------------
'///
'/// SNTP Timestamp Format (as described in RFC 2030)
'/// 1 2 3
'/// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
'/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
'/// | Seconds |
'/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
'/// | Seconds Fraction (0-padded) |
'/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
'///
'///
Public Class SNTPClient
'// NTP Data Structure Length
Private Const SNTPDataLength As Byte = 47
'// NTP Data Structure (as described in RFC 2030)
Dim SNTPData(SNTPDataLength) As Byte
'// Offset constants for timestamps in the data structure
Private Const offReferenceID As Byte = 12
Private Const offReferenceTimestamp As Byte = 16
Private Const offOriginateTimestamp As Byte = 24
Private Const offReceiveTimestamp As Byte = 32
Private Const offTransmitTimestamp As Byte = 40
'Leap Indicator
Public ReadOnly Property LeapIndicator() As _LeapIndicator
Get
'Isolate the two most significant bits
Dim bVal As Byte = (SNTPData(0) >> 6)
Select Case bVal
Case 0 : Return _LeapIndicator.NoWarning
Case 1 : Return _LeapIndicator.LastMinute61
Case 2 : Return _LeapIndicator.LastMinute59
Case 3 : Return _LeapIndicator.Alarm
Case Else : Return _LeapIndicator.Alarm
End Select
End Get
End Property
' Version Number
Public ReadOnly Property VersionNumber() As Byte
Get
'Isolate bits 3 - 5
Dim bVal As Byte = (SNTPData(0) And &H38) >> 3
Return bVal
End Get
End Property
Public ReadOnly Property Mode()
Get
'Isolate bits 0 - 3
Dim bVal As Byte = (SNTPData(0) And &H7)
Select Case bVal
Case 0, 6, 7
Return _Mode.Unknown
Case 1
Return _Mode.SymmetricActive
Case 2
Return _Mode.SymmetricPassive
Case 3
Return _Mode.Client
Case 4
Return _Mode.Server
Case 5
Return _Mode.Broadcast
End Select
End Get
End Property
'Stratum
Public ReadOnly Property Stratum() As _Stratum
Get
Dim bVal As Byte = SNTPData(1)
If (bVal = 0) Then
Return _Stratum.Unspecified
ElseIf (bVal = 1) Then
Return _Stratum.PrimaryReference
ElseIf (bVal <= 15) Then
Return _Stratum.SecondaryReference
Else
Return _Stratum.Reserved
End If
End Get
End Property
'Poll Interval
Public ReadOnly Property PollInterval() As Int32
Get
'// Thanks to Jim Hollenhorst
Return Math.Pow(2, SNTPData(2))
'Return Math.Round(Math.Pow(2, SNTPData(2)))
End Get
End Property
'Precision (in milliseconds)
Public ReadOnly Property Precision() As Double
Get
'// Thanks to Jim Hollenhorst
Return Math.Pow(2, SNTPData(3))
'Return (1000 * Math.Pow(2, SNTPData(3) - 256))
End Get
End Property
'Root Delay (in milliseconds)
Public ReadOnly Property RootDelay() As Double
Get
Dim temp As Int64 = 0
temp = 256 * (256 * (256 * SNTPData(4) + SNTPData(5)) + SNTPData(6)) + SNTPData(7)
Return 1000 * ((temp) / &H10000)
End Get
End Property
'Root Dispersion (in milliseconds)
Public ReadOnly Property RootDispersion() As Double
Get
Dim temp As Int64 = 0
temp = 256 * (256 * (256 * SNTPData(8) + SNTPData(9)) + SNTPData(10)) + SNTPData(11)
Return 1000 * ((temp) / &H10000)
End Get
End Property
'Reference Identifier
Public ReadOnly Property ReferenceID() As String
Get
Dim val As String = ""
Select Case Stratum
Case _Stratum.PrimaryReference Or Stratum.Unspecified
If SNTPData(offReferenceID + 0) <> 0 Then val += Chr(SNTPData(offReferenceID + 0))
If SNTPData(offReferenceID + 1) <> 0 Then val += Chr(SNTPData(offReferenceID + 1))
If SNTPData(offReferenceID + 2) <> 0 Then val += Chr(SNTPData(offReferenceID + 2))
If SNTPData(offReferenceID + 3) <> 0 Then val += Chr(SNTPData(offReferenceID + 3))
Case _Stratum.SecondaryReference
Select Case VersionNumber
Case 3 '// Version 3, Reference ID is an IPv4 address
Dim Address As String = SNTPData(offReferenceID + 0).ToString() + "." + SNTPData(offReferenceID + 1).ToString() + "." + SNTPData(offReferenceID + 2).ToString() + "." + SNTPData(offReferenceID + 3).ToString()
Try
Dim Host As IPHostEntry = Dns.GetHostByAddress(Address)
val = Host.HostName + " (" + Address + ")"
Catch e As Exception
val = "N/A"
End Try
Case 4 '// Version 4, Reference ID is the timestamp of last update
Dim time As DateTime = ComputeDate(GetMilliSeconds(offReferenceID))
'// Take care of the time zone
Dim offspan As TimeSpan = TimeZone.CurrentTimeZone.GetUtcOffset(DateTime.Now)
val = (time.Add(offspan)).ToString()
Case Else
val = "N/A"
End Select
End Select
Return val
End Get
End Property
'// Reference Timestamp
Public ReadOnly Property ReferenceTimestamp() As DateTime
Get
Dim time As DateTime = ComputeDate(GetMilliSeconds(offReferenceTimestamp))
'// Take care of the time zone
Dim offspan As TimeSpan = TimeZone.CurrentTimeZone.GetUtcOffset(DateTime.Now)
Return time.Add(offspan)
End Get
End Property
'// Originate Timestamp
Public ReadOnly Property OriginateTimestamp() As DateTime
Get
Return ComputeDate(GetMilliSeconds(offOriginateTimestamp))
End Get
End Property
'// Receive Timestamp
Public ReadOnly Property ReceiveTimestamp() As DateTime
Get
Dim time As DateTime = ComputeDate(GetMilliSeconds(offReceiveTimestamp))
'Take care of the time zone
Dim offspan As TimeSpan = TimeZone.CurrentTimeZone.GetUtcOffset(DateTime.Now)
Return time.Add(offspan)
End Get
End Property
'// Transmit Timestamp
Public Property TransmitTimestamp() As DateTime
Get
Dim time As DateTime = ComputeDate(GetMilliSeconds(offTransmitTimestamp))
'Take care of the time zone
Dim offspan As TimeSpan = TimeZone.CurrentTimeZone.GetUtcOffset(DateTime.Now)
Return time.Add(offspan)
End Get
Set(ByVal Value As DateTime)
SetDate(offTransmitTimestamp, Value)
End Set
End Property
'// Destination Timestamp
Public DestinationTimestamp As DateTime
'// Round trip delay (in milliseconds)
Public ReadOnly Property RoundTripDelay() As Int64
Get
'// Thanks to DNH
Dim span As TimeSpan = DestinationTimestamp.Subtract(OriginateTimestamp).Subtract(ReceiveTimestamp.Subtract(TransmitTimestamp))
Return span.TotalMilliseconds
End Get
End Property
'// Local clock offset (in milliseconds)
Public ReadOnly Property LocalClockOffset() As Int64
Get
'// Thanks to DNH
Dim span As TimeSpan = ReceiveTimestamp.Subtract(OriginateTimestamp).Add((TransmitTimestamp.Subtract(DestinationTimestamp)))
Return span.TotalMilliseconds / 2
End Get
End Property
'// Compute date, given the number of milliseconds since January 1, 1900
Private Function ComputeDate(ByVal milliseconds As Decimal) As DateTime
Dim span As TimeSpan = TimeSpan.FromMilliseconds(milliseconds)
Dim time As DateTime = New DateTime(1900, 1, 1)
time = time.Add(span)
Return time
End Function
'// Compute the number of milliseconds, given the offset of a 8-byte array
Private Function GetMilliSeconds(ByVal offset As Byte) As Decimal
Dim intPart As Decimal = 0, fractPart As Decimal = 0
Dim i As Int32
For i = 0 To 3
intPart = Int(256 * intPart + SNTPData(offset + i))
Next
For i = 4 To 7
fractPart = Int(256 * fractPart + SNTPData(offset + i))
Next
Dim milliseconds As Decimal = Int(intPart * 1000 + (fractPart * 1000) / &H100000000L)
Return milliseconds
End Function
'// Compute the 8-byte array, given the date
Private Sub SetDate(ByVal offset As Byte, ByVal dateval As DateTime)
Dim intPart As Decimal = 0, fractPart As Decimal = 0
Dim StartOfCentury As DateTime = New DateTime(1900, 1, 1, 0, 0, 0)
Dim milliseconds As Decimal = Int(dateval.Subtract(StartOfCentury).TotalMilliseconds)
intPart = Int(milliseconds / 1000)
fractPart = Int(((milliseconds Mod 1000) * &H100000000L) / 1000)
Dim temp As Decimal = intPart
Dim i As Decimal
For i = 3 To 0 Step -1
SNTPData(offset + i) = Int(temp Mod 256)
temp = Int(temp / 256)
Next
temp = Int(fractPart)
For i = 7 To 4 Step -1
SNTPData(offset + i) = Int(temp Mod 256)
temp = Int(temp / 256)
Next
End Sub
'// Initialize the NTPClient data
Private Sub Initialize()
'Set version number to 4 and Mode to 3 (client)
SNTPData(0) = &H1B
'Initialize all other fields with 0
Dim i As Int32
For i = 1 To 47
SNTPData(i) = 0
Next
'Initialize the transmit timestamp
TransmitTimestamp = DateTime.Now
End Sub
Public Sub New(ByVal host As String)
TimeServer = host
End Sub
'// Connect to the time server and update system time
Public Function Connect(ByVal UpdateSystemTime As Boolean) As Boolean
Try
'Resolve server address
Dim hostadd As IPHostEntry = Dns.Resolve(TimeServer)
Dim EPhost As IPEndPoint = New IPEndPoint(hostadd.AddressList(0), 123)
'Connect the time server
Dim TimeSocket As UdpClient = New UdpClient
TimeSocket.Connect(EPhost)
'Initialize data structure
Initialize()
TimeSocket.Send(SNTPData, SNTPData.Length)
SNTPData = TimeSocket.Receive(EPhost)
If IsResponseValid() = False Then
Throw New Exception("Invalid response from " + TimeServer)
End If
DestinationTimestamp = DateTime.Now
Catch e As SocketException
Throw New Exception(e.Message)
End Try
'// Update system time
If (UpdateSystemTime) Then
SetTime()
End If
End Function
'// Check if the response from server is valid
Public Function IsResponseValid() As Boolean
If (SNTPData.Length < SNTPDataLength Or Mode <> _Mode.Server) Then
Return False
Else
Return True
End If
End Function
'// Converts the object to string
Public Overrides Function ToString() As String
Dim str As String
Dim sb As New StringBuilder("")
sb.Append("Leap Indicator: ")
Select Case LeapIndicator
Case _LeapIndicator.NoWarning
sb.Append("No warning")
Case _LeapIndicator.LastMinute61
sb.Append("Last minute has 61 seconds")
Case _LeapIndicator.LastMinute59
sb.Append("Last minute has 59 seconds")
Case _LeapIndicator.Alarm
sb.Append("Alarm Condition (clock not synchronized)")
End Select
sb.Append(vbCrLf & "Version number: " + VersionNumber.ToString())
sb.Append(vbCrLf & "Mode: ")
Select Case Mode
Case _Mode.Unknown
sb.Append("Unknown")
Case _Mode.SymmetricActive
sb.Append("Symmetric Active")
Case _Mode.SymmetricPassive
sb.Append("Symmetric Pasive")
Case _Mode.Client
sb.Append("Client")
Case _Mode.Server
sb.Append("Server")
Case _Mode.Broadcast
sb.Append("Broadcast")
End Select
sb.Append(vbCrLf & "Stratum: ")
Select Case Stratum
Case _Stratum.Unspecified
Case _Stratum.Reserved
sb.Append("Unspecified")
Case _Stratum.PrimaryReference
sb.Append("Primary Reference")
Case _Stratum.SecondaryReference
sb.Append("Secondary Reference")
End Select
sb.Append(vbCrLf & "Local time: " + TransmitTimestamp.ToString())
sb.Append(vbCrLf & "Precision: " + Precision.ToString() + " ms")
sb.Append(vbCrLf & "Poll Interval: " + PollInterval.ToString() + " s")
sb.Append(vbCrLf & "Reference ID: " + ReferenceID.ToString())
sb.Append(vbCrLf & "Root Delay: " + RootDelay.ToString() + " ms")
sb.Append(vbCrLf & "Root Dispersion: " + RootDispersion.ToString() + " ms")
sb.Append(vbCrLf & "Round Trip Delay: " + RoundTripDelay.ToString() + " ms")
sb.Append(vbCrLf & "Local Clock Offset: " + LocalClockOffset.ToString() + " ms")
sb.Append(vbCrLf)
Return sb.ToString
End Function
'// SYSTEMTIME structure used by SetSystemTime
Private Structure SYSTEMTIME
Public year As Int16
Public month As Int16
Public dayOfWeek As Int16
Public day As Int16
Public hour As Int16
Public minute As Int16
Public second As Int16
Public milliseconds As Int16
End Structure
Private Shared Function SetLocalTime(ByRef time As SYSTEMTIME) As Int32
End Function
'// Set system time according to transmit timestamp
Private Sub SetTime()
Dim x As Boolean
Dim st As SYSTEMTIME
Dim trts As DateTime = DateTime.Now.AddMilliseconds(LocalClockOffset)
st.year = trts.Year
st.month = trts.Month
st.dayOfWeek = trts.DayOfWeek
st.day = trts.Day
st.hour = trts.Hour
st.minute = trts.Minute
st.second = trts.Second
st.milliseconds = trts.Millisecond
SetLocalTime(st)
End Sub
'// The URL of the time server we're connecting to
Private TimeServer As String
End Class
End Namespace