Check for valid IMEI
Does anybody know how to check for a valid IMEI?
I have found a function to check on this page: http://www.dotnetfunda.com/articles/article597-imeivalidator-in-vbnet-.aspx
But it returns false
for valid IMEI's (f.e. 352972024585360
).
I can validate them online on this page: ht开发者_如何转开发tp://www.numberingplans.com/?page=analysis&sub=imeinr
What is the correct way(in VB.Net) to check if a given IMEI is valid?
PS: This function from above page must be incorrect in some way:
Public Shared Function isImeiValid(ByVal IMEI As String) As Boolean
Dim cnt As Integer = 0
Dim nw As String = String.Empty
Try
For Each c As Char In IMEI
cnt += 1
If cnt Mod 2 <> 0 Then
nw += c
Else
Dim d As Integer = Integer.Parse(c) * 2 ' Every Second Digit has to be Doubled '
nw += d.ToString() ' Genegrated a new number with doubled digits '
End If
Next
Dim tot As Integer = 0
For Each ch As Char In nw.Remove(nw.Length - 1, 1)
tot += Integer.Parse(ch) ' Adding all digits together '
Next
Dim chDigit As Integer = 10 - (tot Mod 10) ' Finding the Check Digit my Finding the Remainder of the sum and subtracting it from 10 '
If chDigit = Integer.Parse(IMEI(IMEI.Length - 1)) Then ' Checking the Check Digit with the last digit of the Given IMEI code '
Return True
Else
Return False
End If
Catch ex As Exception
Return False
End Try
End Function
EDIT: This is my working "checkIMEI"-Function:
Public Shared Function checkIMEI(ByRef IMEI As String) As Boolean
Const allowed As String = "0123456789"
Dim cleanNumber As New System.Text.StringBuilder
For i As Int32 = 0 To IMEI.Length - 1
If (allowed.IndexOf(IMEI.Substring(i, 1)) >= 0) Then
cleanNumber.Append(IMEI.Substring(i, 1))
End If
Next
If cleanNumber.Length <> 15 Then
Return False
Else
IMEI = cleanNumber.ToString
End If
For i As Int32 = cleanNumber.Length + 1 To 16
cleanNumber.Insert(0, "0")
Next
Dim multiplier As Int32, digit As Int32, sum As Int32, total As Int32 = 0
Dim number As String = cleanNumber.ToString()
For i As Int32 = 1 To 16
multiplier = 1 + (i Mod 2)
digit = Int32.Parse(number.Substring(i - 1, 1))
sum = digit * multiplier
If (sum > 9) Then
sum -= 9
End If
total += sum
Next
Return (total Mod 10 = 0)
End Function
IMEI numbers are validated using the Luhn algorithm. The linked page has implementations in various languages. This post also has a few more implementations and a general methodology on how to go about solving the Luhn algorithm.
IMEISV(IMEI software version) does not have Luhn algorithm check digit. Instead it has Software Version Number presented with two digits. Format of IMEI number has been evolving by years.
Wikipedia is the good source I think to see the changes in the format by years. If you look the new IMEI and IMEISV version format, you would see that Final Assembly Code(FAC) has removed and Type Allocation Code(TAC) was increased the 8 digit. There are free and commercial TAC lists exist on the internet.
it could be an option to validate TAC number by looking up the TAC lists on top of Luhn algorithm validation for new and old IMEI numbers. For old IMEI numbers FAC as 2 digit should be discarded and TAC validation should be done for 6 digits.
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