This post originally appeared on the Annexe.

A useful set of flags is the delightful “plunt”

# netstat -plunt

For example, on a PostgreSQL box with custom ports:

Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address       Foreign Address         State       PID/Program name
tcp    0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      1077/sshd       
tcp    0      0 127.0.0.1:5432          0.0.0.0:*               LISTEN      2288/postgres   
tcp6   0      0 :::22                   :::*                    LISTEN      1077/sshd       
tcp6   0      0 ::1:5432                :::*                    LISTEN      2288/postgres