netstat

Displays network-related information such as open connections, open socket ports, etc. More information: https://www.unix.com/man-page/osx/1/netstat.

List all ports:

netstat -a

List all listening ports:

netstat -l

List listening TCP ports:

netstat -t

Display PID and program names for a specific protocol:

netstat -p {{protocol}}

Print the routing table:

netstat -nr