netstat

Display network-related information such as open connections, open socket ports, etc. More information: https://manned.org/netstat.

• List all ports:

netstat --all

• List all listening ports:

netstat --listening

• List listening TCP ports:

netstat --tcp

• Display PID and program names:

netstat --program

• List information continuously:

netstat --continuous

• List routes and do not resolve IP addresses to hostnames:

netstat --route --numeric

• List listening TCP and UDP ports (+ user and process if you're root):

netstat --listening --program --numeric --tcp --udp --extend