Unreachable content (Docker containers) on other ports than 80

Hello everybody,

I have a problem accessing Docker containers for any other port than 80. Previously it worked and I had services accessibles on ports 5000 and 7000 in addition to a nginx server installed directly on the droplet. I recently do a dist-upgrade to Ubuntu 18.04.1 LTS and that may have broken stuff.

What works:

• accessing a page on port 80 or 443 served by nginx (without docker)
• accessing my docker container from another machine if bind on port 80
• accessing my docker container from the localhost regardless of port

What doesn’t work:

• accessing a page on port 81 served by nginx (without docker)
• accessing my docker container if bind to port 5000 or 7000

So it seems there is a problem with other ports than 80 and 443 for serving content on the internet. I have no digital ocean firewall configured. I tried to look iptables stuff but I understand very little and don’t manage to find anything suspicious.

I would need your help to solve this case.