SOLVED - Help - Exposing container port outside

I’m a developer and I’m completely new with
I’m having an issue exposing the port of a container to the outside.

I deploy my container in the device, which has an exposed port 8443.
I log on the device and I add the port redirection from the device to the container. (as instructed in the FAQs:

iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 8443 -j REDIRECT --to-port 8443

But when I try to access the public webpage, I get no page.

PS: when using docker directly in my PC (using Docker toolbox)
1 - replacing base image: resin/raspberrypi3-alpine-openjdk:openjdk-8-jre for openjdk:8-jre
2 - I can run and access the published webpage using the following command:

docker run -it -d -p 8443:8443 --name sample-site joaocarloscg/container-sample:latest

Am I missing any important step?

Edit: the ports are automatically exposed, the issue was elsewhere. to close/delete