The attribute "ports" defines the mapping from external to internal port of a docker container (left=external, right = internal: 8080:8080).
Don't change the internal port, only the external port when setting up a new FROST-Server container (i.e. keep 8080 AND 1883 fixed).

For the (default) case that FROST-server shall be reachable at the standard server adresse (can be URL or IP) but with generic port adress:

services:

  web:

    image: fraunhoferiosb/frost-server:latest

    environment:

      - serviceRootUrl=http://<IP-adresse/main-server-URL>:<PORT-number>/FROST-Server

      - ...

    ports:

      - 8080:8080

      - 1883:1883

For the case that FROST-server shall be reachable at a specific URL, it must be specified to be reachable inside only from the localhost (127.0.0.1) and from outside only by a reverse proxy (needs to be configured elsewhere at e.g. apache or Tomcat server):

services:

  web:

    image: fraunhoferiosb/frost-server:latest

    environment:

      - serviceRootUrl=https://sensor-server.hef.tum.de/frost

      - ...

    ports:

      - 127.0.0.1:8080:8080

      - 127.0.0.1:1883:1883