Getting the IP Address of the user browsing your site?

 What I have right now gets an IP address but I think it's the IP of the server rather than the user and I need it to be unique to the user for preventing repeated voting in a poll.
 
    Function GetIP() As String
        Dim IP As IPHostEntry = New IPHostEntry
        IP = Dns.Resolve(Dns.GetHostName)

        Dim arrIP() As IPAddress = IP.AddressList
        Dim IPstring As String = arrIP(0).ToString()

        Label3.Text = IPstring
        Return IPstring

    End Function

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