BTW, I’ve just checked the port 80/443 and it seems that the Docker are using these ports.
root@discourse:~# netstat -punta | grep 443
tcp6 0 0 :::443 :::* LISTEN 1301/docker-proxy
root@discourse:~# netstat -punta | grep 80
tcp6 0 0 :::80 :::* LISTEN 1324/docker-proxy
tcp6 0 0 fe80::c0a:f3ff:fe81::53 :::* LISTEN 1115/dnsmasq
udp6 0 0 fe80::c0a:f3ff:fe81::53 :::* 1115/dnsmasq