How to convert IP address to country name

• Download source code - 1.11 MB

How to retrieve a visitor's IP address

Every visitor to your site or web application has an IP address. It is quite handy to be able to get that address. It can be used for security logging, or perhaps tracing. It can also be used to determine where they are in the world, or at least where their ISP is.

The difficulty is when they are behind a proxy of some sort, and you can only see the IP address of the proxy server. So, here are the code snippets in ASP.NET that first check for an IP addresses that's forwarded from behind a proxy, and if there's none, then just gets the IP address. Here's the same IP retriever with proxy detection in .NET, but in VB.NET:

Dim nowip As String 
nowip = Request.ServerVariables("HTTP_X_FORWARDED_FOR") 
If nowip = "" Then
   nowip = Request.ServerVariables("REMOTE_ADDR")
End If

How do I convert an IP address to an IP number?

IP address (IPV4) is divided into four sub-blocks. Each sub-block has a different weight number, each powered by 256. The IP number is being used in the database because it is efficient to search between a range of numbers in the database.

The beginning IP number and the ending IP number are calculated based on the following formula:

IP Number = 16777216*w + 65536*x + 256*y + z (1)

where:

IP Address = w.x.y.z

For example, if the IP address is "202.186.13.4", then its IP number is "3401190660" based on the above formula.

IP Address = 202.186.13.4
So, w = 202, x = 186, y = 13 and z = 4

IP Number = 16777216*202 + 65536*186 + 256*13 + 4
          = 3388997632 + 12189696 + 3328 + 4
          = 3401190660

To reverse the IP number to the IP address:

w = int ( IP Number / 16777216 ) % 256
x = int ( IP Number / 65536 ) % 256
y = int ( IP Number / 256 ) % 256
z = int ( IP Number ) % 256

where, % is the mod operator and int returns the integer part of the division.

How do I retrieve the country name and the country code from the IP number?

Search the IP-country database to match a unique record that has the IP number that fits between the beginning IP number and the ending IP number.

For example, the IP address "202.186.13.4" is equivalent to the IP number "3401190660". It belongs to the following record in the database because it is between the beginning and the the ending of the IP number:

"3401056256","3401400319","MY","MALAYSIA"

From the recordset, the country name is Malaysia and the country code is MY. Here is a useful link.

How do I use this database

CSV file format

The CSV file contains four fields:

• Beginning of the IP address range
• Ending of the IP address range
• Two-character country code based on ISO 3166
• Three-character country code based on ISO 3166
• Country name based on ISO 3166

"0033996344","0033996351","GB","GBR","UNITED KINGDOM"
"0050331648","0083886079","US","USA","UNITED STATES"
"0094585424","0094585439","SE","SWE","SWEDEN"

Download CSV database

• Download the latest IP-to-Country database (Last updated on July 21 2008).
• The IP-to-Country Handbook

Convert to Access database

Here is the code-behind:

Partial Class How_to_Convert_IP_Address_Country _
        Inherits System.Web.UI.Page

    Protected Sub Page_Load(ByVal sender As Object,_
        ByVal e As System.EventArgs) Handles Me.Load
        Dim nowip As String
        nowip = Request.ServerVariables("HTTP_X_FORWARDED_FOR")
        If nowip = "" Then
            nowip = Request.ServerVariables("REMOTE_ADDR")
        End If

        If txtIPAddress.Text = "" Then
            txtIPAddress.Text = nowip
        End If
        lblError.Text = ""
    End Sub

    Protected Sub Button1_Click(ByVal sender As Object,_
        ByVal e As System.EventArgs) Handles Button1.Click
        On Error GoTo HandleError

        Dim dottedip As String
        Dim Dot2LongIP As Double
        Dim PrevPos As Double
        Dim pos As Double
        Dim num As Double

        dottedip = txtIPAddress.Text

            For i = 1 To 4
                pos = InStr(PrevPos + 1, dottedip, ".", 1)
                If i = 4 Then
                    pos = Len(dottedip) + 1
                End If
                num = Int(Mid(dottedip, PrevPos + 1, pos - PrevPos - 1))
                PrevPos = pos
                Dot2LongIP = ((num Mod 256) * (256 ^ (4 - i))) + Dot2LongIP
            Next

        txtIPNumber.Text = Dot2LongIP

HandleError:
        lblError.Text = Err.Description
    End Sub
End Class

Here is the output:

• Try a demo here.