Testing for a firewall

akm2 has asked for the wisdom of the Perl Monks concerning the following question:

My fellow monks I have yet another question to put before you.

I need a .cgi that will test and see if a user is behind a firewall. If so I need to make sure that ports 3380 and 3389 are not blocked. if they are blocked, I need to display an error message.

I need this script so I can test and see if said user is going to be able to connect to our Windows 2000 Terminal Server.

Can anybody give me some example code, ideas, thoughts, or advice on how to do this?

Thanks in advance,

Andrew Kenton Mitchell
Andrew@AndrewKMitchell.com

Comment on Testing for a firewall

Replies are listed 'Best First'.
Re: Testing for a firewall by echo (Pilgrim) on Aug 22, 2001 at 19:15 UTC
The client might be able to connect to port 3380, while a connection from the server to the client might be forbidden. In other words the firewall might (and they usually do) implement a different ruleset for outgoing connections and incoming ones. Therefore I wager there is no way you can achieve what you want, short of asking the client to connect (or triggering that with a Java applet) and seeing if it comes through.	[reply]
Re: Testing for a firewall by MZSanford (Curate) on Aug 22, 2001 at 19:12 UTC
Hmmmm, If you want to be able to connect to them on ports 3380 and 3389, i would probably use `IO::Socket` and open a connection with a short (maybe 10 sec ?) timeout, and then use the return code to say if the ports are open. About the only real way i can think of. but, if i am confussed, and i am quite a bit lately, and you want to find out if they could connect to you ... i am not sure of anyway ... but, i am not a CGI programmer. Update : Could you possibly pop another browser window to another http server on port 3380 of you machine (or any machine) and ask the user to confirm that that has loaded ? but, beware, users lie _{can't sleep clowns will eat me} -- MZSanford	[reply] [d/l]


Come for the quick hacks, stay for the epiphanies.
	PerlMonks