My school has a firewall which limits most outgoing ports. There're only
TCP/21 allowed. Is there's a way to find out all the outgoing port allowed by the firewall?
My current idea: open all TCP ports with
nc on a remote server, then use
nmap to scan which ports are accessible. But how do I do if I don't have a remote server? or is there a public server that opens all the ports for this kind of tests?