Convert Dotted Quad IP Address to Long IP Address and Vice Versa

Category:

Network/Internet

Type:

Snippets

Difficulty:

Intermediate

Author:

Rick

Version Compatibility:

More information:

IP Addresses are 32-bit values which are typically represented as 8-bit quadruplets (or "dotted quads"). These functions allow you to convert between dotted quad values and long IP addresses (the 32-bit values). You can use the 32-bit value in most internet clients (i.e., web browser, FTP client) instead of the dotted quads or the domain name.

Instructions: Copy the declarations and code below and paste directly into your VB project.

Declarations:
' (None)

Code:

Public Function Dotted2LongIP(DottedIP As String) As Variant
    ' errors will result in a zero value
    On Error Resume Next

Dim i As Byte, pos As Integer
    Dim PrevPos As Integer, num As Integer

' string cruncher
    For i = 1 To 4
        ' Parse the position of the dot
        pos = InStr(PrevPos + 1, DottedIP, ".", 1)

' If its past the 4th dot then set pos to the last
        'position + 1

If i = 4 Then pos = Len(DottedIP) + 1

' Parse the number from between the dots

num = Int(Mid(DottedIP, PrevPos + 1, pos - PrevPos - 1))

' Set the previous dot position
        PrevPos = pos

' No dot value should ever be larger than 255
        ' Technically it is allowed to be over 255 -it just
        ' rolls over e.g.
         '256 => 0 -note the (4 - i) that's the 
         'proper exponent for this calculation

Dotted2LongIP = ((num Mod 256) * (256 ^ (4 - i))) + _
         Dotted2LongIP

End Function

' convert long IP to dotted notation

Public Function LongIP2Dotted(ByVal LongIP As Variant) As String

On Error GoTo ExitFun

If LongIP = "" Or LongIP < 0 Then Err.Raise vbObjectError + 1

Dim i As Integer, num As Currency

' big number cruncher
    For i = 1 To 4
        ' break off individual dot values - math out the wazoo
        num = Int(LongIP / 256 ^ (4 - i))

' sets up the value for the next calculation
        LongIP = LongIP - (num * 256 ^ (4 - i))

' a generic error to flag the exception handler - 
        'no dot value should ever be larger than 255
        ' technically it is allowed to be over 255
        ' but it's not possible from this calculation so 
        'raise an error
        If num > 255 Then Err.Raise vbObjectError + 1

' string builder
        If i = 1 Then
            ' 1st dot value has no leading dot
            LongIP2Dotted = num
        Else
            ' other dot values have a leading dot
            LongIP2Dotted = LongIP2Dotted & "." & num
        End If
    Next

Exit Function
ExitFun:
     LongIP2Dotted = "0.0.0.0" '"Invalid Input" ' whatever
End Function