RealVNC Cloud Connect needs port 5900 open to work

I am trying to use RealVNC 6.1.x as a remote control application over the internet. The documentation is not very clear but from my experiments it seems like it needs port 5900 needs to be opened to the internet.

So RealVNC Cloud Connect is not similar to TeamViwer. This can be deal breaker in NAT (home configuration) or small office where only ports 80 and 443 are allowed.