Here is code to get the IP Address For User Tracking

Public Shared Function GetIPAddress() As String
        Dim sIPAddress As String
        sIPAddress = HttpContext.Current.Request.ServerVariables("HTTP_X_FORWARDED_FOR")
        If sIPAddress = "" Then
            sIPAddress = HttpContext.Current.Request.ServerVariables("REMOTE_ADDR")
        End If
        Return sIPAddress
    End Function

if ( isset( $_SERVER['HTTP_X_FORWARDED_FOR'] ) && $_SERVER['HTTP_X_FORWARDED_FOR'] != '')
		{ 
 	   $sIP = $_SERVER['HTTP_X_FORWARDED_FOR']; 
 	   $sProxy = $_SERVER['REMOTE_ADDR']; 
 	   $sHost = @gethostbyaddr($_SERVER['HTTP_X_FORWARDED_FOR']); 
		}
		elseif ( isset( $_SERVER['REMOTE_ADDR'] ) )
		{ 
 	   $sIP = $_SERVER['REMOTE_ADDR']; 
 	   $sHost = @gethostbyaddr($_SERVER['REMOTE_ADDR']); 
		}