This is the list of all ports required by a regular ggRock installation
Debian Control Panel
Prometheus Node Exporter (Stats collection)
Additionally we configure port forwarding on ggRock server (we use it as the default gateway for client PCs that forwards Internet/external traffic to the main gateway in LAN). In such configuration all ports, that should be forwarded to internet/external networks, should also be opened in local firewall.
See the ggRock FAQ for additional information.