Is Port 8766 Required?

[SuckaFreeSunday]

I am running a Project Zomboid server on my Synology DS920+ NAS via the renegademaster docker image, and I'm wondering why port 8766 is required if it's not something you can specify in your client "Join Server" settings. I disabled that port on the docker container, and I was able to connect to the server just fine with just 16261. I'm hoping to run at least two Zomboid servers on the same machine, so I'm trying to understand which ports I actually need opened. If 8766 doesn't need to be open, then I'm in the clear. If 8766 IS required, then I need to figure out how my players would specify that in their settings.

 

Thank you!