To list the open ports together with the listening processes:
netstat -tulpn
Here is an example output:
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 695/sshd tcp6 0 0 :::22 :::* LISTEN 695/sshd udp 0 0 0.0.0.0:55872 0.0.0.0:* 407/avahi-daemon: r udp 0 0 0.0.0.0:68 0.0.0.0:* 694/dhcpcd udp 0 0 10.7.0.70:123 0.0.0.0:* 722/ntpd udp 0 0 127.0.0.1:123 0.0.0.0:* 722/ntpd udp 0 0 0.0.0.0:123 0.0.0.0:* 722/ntpd udp 0 0 0.0.0.0:5353 0.0.0.0:* 407/avahi-daemon: r udp6 0 0 :::546 :::* 694/dhcpcd udp6 0 0 fe80::a9be:bf0c:367:123 :::* 722/ntpd udp6 0 0 2a02:810d:19c0:7748:123 :::* 722/ntpd udp6 0 0 ::1:123 :::* 722/ntpd udp6 0 0 :::123 :::* 722/ntpd udp6 0 0 :::5353 :::* 407/avahi-daemon: r udp6 0 0 :::51486 :::* 407/avahi-daemon: r