Re: How to check what ports are filtered on a public network?

[Pascal Hambourg <pascal@plouf.fr.eu.org>]

jugree@lavabit.com a écrit :
> 
> Some public networks don't allow to connect to port 25 or forbid
> non-http traffic. How to check what ports are filtered/blocked? I
> think it can be done with nmap, but I have never used it.

Yes, but you need to have a remote host with the TCP ports your want to
check opened and listening, and ideally, UDP ports you want to check
opened, listening and replying to incoming datagrams (such as an "echo"
service).