Cisco IOS show listening ports
You can see which ports the router is listening on with this command:
R1#show control-plane host open-ports Active internet connections (servers and established) Prot Local Address Foreign Address Service State tcp *:22 *:0 SSH-Server LISTEN tcp *:23 *:0 Telnet LISTEN tcp *:443 *:0 TCP Listener LISTEN
For the ASA, check this: