Collabora Docker: Connection Server to Server or Client to Server?

Hi all,

I am planning installation of Collabora to an existing Nextcloud system. But one thing is a little unclear to me - how is the connection done?

Understood: I (Host A) connect to the Nextcloud Server (Host B). There the Collabora addon needs to be installed, where I put the hostname of the Host (Host C) that runs Collabora Docker and Reverse Proxy.

Unclear to me: how is the connection towards Host C running Collabora Docker done: Is this a direct connection from the NExtcloud User Client (Host A), or is this coming from Host B? I’m asking because in my setup both Hosts (B and C) are sitting behind a NAT’d firewall and I need to care for port forwardings.

Furthermore: if there is a connection needed between Host A and Host C (which is what I guess is required), can I change the SSL port the Apache Reverse Proxy on Host C (Docker Interface) listens at - and supply the hostname in the Nextcloud App Config in the way of, eg. (taking alternate port 8443) - does the addon understand this port number and will use it? I cannot take 443, as this is already used by the Nextcloud host (Host B) in the given configuration, and a NAT forward rule is present already for this port thus.

Best Regards, and thanks for your help,