Page 15 - DCAP202_Fundamentals of Web Programming

Fundamentals of Web Programming
Notes
8 LOVELY PROFESSIONAL UNIVERSITY
The order Preferred networks determines the order that Windows XP will automatically attempt
when seeking to make a wireless/Internet connection. You can set this order to your preference,
with the limitation that all infrastructure mode networks must appear ahead of all ad hoc mode
networks in the Preferred list.
Self Assessment
Fill in the blanks:
8. ........................... splits the signal in the telephone wire in two: voice and broadband.
9. The ........................... tab allows you to access the set of "Available" networks.
1.5 Client IP Address
It's pretty common the need for a web application to be able to detect the IP address of a client.
The IP address could be used either for statistic or authentication purposes.
You can also use the IP address to block multiple logins with the same credentials. This could be
useful for sites that offer content to users that have paid a subscription.
1.5.1 Using the Code
The code to do so is really easy, all you need to do is check a bunch of server variables. The good
thing is that those variables are not platform specific, so an equivalent code could also work
with PHP.
Function ClientIpAddress(ByVal myRequest As HttpRequest)
Dim myIP As String = “”
If (myIP = “”) Then
myIP = myRequest.ServerVariables(“HTTP_CLIENT_IP”)
If (myIP = “”) Then myIP =
myRequest.ServerVariables(“HTTP_X_FORWARDED_FOR”)
If (myIP = “”) Then myIP =
myRequest.ServerVariables(“HTTP_X_FORWARDED”)
If (myIP = “”) Then myIP =
myRequest.ServerVariables(“HTTP_ X_CLUSTER_CLIENT_IP”)
If (myIP = “”) Then
myIP = myRequest.ServerVariables(“HTTP_FORWARDED_FOR”)
If (myIP = “”) Then
myIP = myRequest.ServerVariables(“HTTP_FORWARDED”)
If (myIP = “”) Then
myIP = myRequest.ServerVariables(“REMOTE_ADDR”)
Return myIP
End Function
Sometimes though we do not have the actual IP address but we have the host name of the ISP
provider of the client. The host name can be easily resolved into an IP address easily. Using the
System.Net.Dns.GetHostEntry function we get a list of all the IP addresses this hostname resolves
to.
Function Host2Ip(ByVal HostName As String) As String
Try
Dim myIPs As System.Net.IPHostEntry
myIPs = System.Net.Dns.GetHostEntry(HostName)