Server 220.127.116.1185 running on FreeBSD
I have the server installed behind a linux router, NAT out to the internet. I have no (apparent) problem configuring remote access when I NAT the default port (32400) to the plex host.
I would prefer the public IP accept Plex connections on a non-default port. To this end, I've tried the 'Manually specify public port' option, but have observed a really strange behavior as soon as this is enabled. The server seems to drop off of the web UI entirely. Not unavailable or unreachable... not listed at all. The web UI only lists my other plex server running elsewhere.
I'm able to restore the instance by moving Preferences.xml aside and re-joining the server to my account. This of course also resets the public port, at which point things seem normal-ish again.