Calculating CheckSum from String with VB6

Question

Hi there,

I need help please calculating the checksum of a string on Visual Basic 6!

String = "50 44 57 31 32" the checksum should be 14E but I cannot figure out a way of writing the VB6 formula.

In my code, I manipulate the string message, convert to HEX and then should calculate the CheckSum + add (i.e. not mathematical addition) to "newString"

My VB6 code:

Public Sub sendPDW()

Dim strTemp As String
Dim strTempPDWsData As String
Dim strTempPDWsData2 As String
Dim strReturn As String
Dim I As Long
Dim SendPDW As String
Dim strToHex As String
Dim hexTemp2 As String
'Declare CheckSum Variables... as Long?
...

...

PDWsData = " 12"

'STRING MANIPULATION BY REMOVING THE SPACE
strTempPDWsData = Mid$(PDWsData, 2) 'PDWsData = "12"

'COMBINE WITH COMMAND
strTempPDWsData2 = "PDW" & strTempPDWsData 'strTempPDWsData2 = "PDW12"

'STRING DATA CONVERSION TO HEX
For I = 1 To Len(strTempPDWsData2)
strTemp = Hex$(Asc(Mid$(strTempPDWsData2, I, 1)))
If Len(strTemp) = 1 Then strTemp = "0" & strTemp
strToHex = strToHex & Space$(1) & strTemp
Next I

'strToHex = " 50 44 57 31 32" & "CS"

'STRING MANIPULATION BY REMOVING THE SPACE
hexTemp2 = Mid$(strToHex, 2) 'hexTemp2 = "50 44 57 31 32 CS"

...
'CheckSum Calculation of hexTemp2 in VB6 + Replace CS with CheckSum value
'Define code here

'CheckSum value = ????
'hexTemp2 + CheckSum value = newString
'Expected newString = "50 44 57 31 32 14E"
...

SendPDW = newString

If Winsock1.State = 7 Then
Winsock1.SendData (SendPDW)
End If

End Sub

Thank you!!!

Answer 1

Hi

Since this is a "VB dot NET" forum, here is code that may help (it's up to you to amend for VB6)

 Dim input As String = "50 44 57 31 32"

 Dim hx() As String = Split(input, " "c)

 Dim tot As Integer = 0
 For i As Integer = 0 To hx.Count - 1
 tot += Convert.ToInt32(hx(i), 16)
 Next

 Dim res As String = Hex(tot)
 ' tot =  334  (Integer) = 14E  (Hex)
 ' res = "14E" (string)