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RunCommand Constants

Terms of Use


 

General: Validate an IP Address

Author(s)
Paul Overway
Here is a snippet of code for validating an IP address. It is a string function that assures that the IP address is correctly formed.
'   ***** Code Start *****
Function IsValidIP(Arg As String) As Boolean

On Error Resume Next

Dim i As Integer
Dim intCount As Integer
Dim strTemp As String
Dim strOut As String
Dim strToken As String

'Too many or not enough characters
If Len(Arg) > 15 Or Len(Arg) < 7 Then
Arg = ""
Exit Function
End If

For i = 1 To Len(Arg)
If Mid(Arg, i, 1) = "." Then
intCount = intCount + 1
End If

'Bail if bad character
If InStr("1234567890.", Mid(Arg, i, 1)) = 0 Then
Arg = ""
Exit Function
End If

Next

'Not enough periods
If intCount <> 3 Then
Arg = ""
Exit Function
End If

'Can't start with period
If Mid(Arg, 1, 1) = "." Then
Arg = ""
Exit Function
End If

strTemp = Arg

For i = 1 To 4

If InStr(strTemp, ".") Then
strToken = Mid(strTemp, 1, InStr(strTemp, ".") - 1)
Else
strToken = strTemp
End If

'Empty token...bail
If Len(strToken) = 0 Then
Arg = ""
Exit Function
End If

If CInt(strToken) > 255 Then
'Token value too high
Arg = ""
Exit Function
Else
'OK
strOut = strOut & CInt(strToken) & "."
End If

'Lop it for next part
If InStr(strTemp, ".") Then
strTemp = Mid(strTemp, InStr(strTemp, ".") + 1)
End If
Next

strOut = Left(strOut, Len(strOut) - 1)

If strOut = Arg Then
IsValidIP = True
Else
'Arg was bad, but fixable. Return corrected version of Arg
Arg = strOut
IsValidIP = False
End If

End Function
'   ***** Code End  *****

1998-2009, Dev Ashish & Arvin Meyer, All rights reserved. Optimized for Microsoft Internet Explorer