netstat

sudo netstat -tnlp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 127.0.1.1:53            0.0.0.0:*               LISTEN      1268/dnsmasq
tcp        0      0 0.0.0.0:21              0.0.0.0:*               LISTEN      1105/sshd
tcp        0      0 127.0.0.1:631           0.0.0.0:*               LISTEN      766/cupsd
tcp6       0      0 :::21                   :::*                    LISTEN      1105/sshd
tcp6       0      0 ::1:631                 :::*                    LISTEN      766/cupsd