I entered the command, here is the output:
Chain INPUT (policy ACCEPT 9 packets, 648 bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
16012 108M DOCKER-USER all -- * * 0.0.0.0/0 0.0.0.0/0
16012 108M DOCKER-ISOLATION-STAGE-1 all -- * * 0.0.0.0/0 0.0.0.0/0
7953 107M ACCEPT all -- * docker0 0.0.0.0/0 0.0.0.0/0 ctstate RELATED,ESTABLISHED
86 4460 DOCKER all -- * docker0 0.0.0.0/0 0.0.0.0/0
7973 807K ACCEPT all -- docker0 !docker0 0.0.0.0/0 0.0.0.0/0
0 0 ACCEPT all -- docker0 docker0 0.0.0.0/0 0.0.0.0/0
Chain OUTPUT (policy ACCEPT 8 packets, 600 bytes)
pkts bytes target prot opt in out source destination
Chain DOCKER (1 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- !docker0 docker0 0.0.0.0/0 172.17.0.2 tcp dpt:443
15 780 ACCEPT tcp -- !docker0 docker0 0.0.0.0/0 172.17.0.2 tcp dpt:80
Chain DOCKER-ISOLATION-STAGE-1 (1 references)
pkts bytes target prot opt in out source destination
7973 807K DOCKER-ISOLATION-STAGE-2 all -- docker0 !docker0 0.0.0.0/0 0.0.0.0/0
16012 108M RETURN all -- * * 0.0.0.0/0 0.0.0.0/0
Chain DOCKER-ISOLATION-STAGE-2 (1 references)
pkts bytes target prot opt in out source destination
0 0 DROP all -- * docker0 0.0.0.0/0 0.0.0.0/0
7973 807K RETURN all -- * * 0.0.0.0/0 0.0.0.0/0
Chain DOCKER-USER (1 references)
pkts bytes target prot opt in out source destination
16012 108M RETURN all -- * * 0.0.0.0/0 0.0.0.0/0
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
1ddff40f95d2 local_discourse/app "/sbin/boot" 4 minutes ago Up 4 minutes 0.0.0.0:80->80/tcp, 0.0.0.0:443->443/tcp app