first of all, we have an application example to demonstrate how to properly configure our nginx reverse proxy that is embeded in the Industrial Edge Runtime.
See how to use it here: https://github.com/industrial-edge/hello-world
To communicate between two docker container you can have a look on our more comprehensive developer guide https://github.com/industrial-edge/Developer-Guide-Hands-on-App that demonstrate how to create multicontainer Edge application which are based on docker-compose.yml file.
In general if you use docker compose command to build your docker apps you can use the service name in the docker-compose.yml file as a DNS to communicatte with other containers in the same docker network.
Benefit of using our nginx sever is that we take care of the certificate handling for you so highly recomend to use it and also you can access your applicaton remotely from IEM on your IED.
For example here: To communicate with an MQTT broker you can use "mqtt-broker" instead of an IP address of the broker. docker-compose.yml