For testing on our UOW project I needed two virtual machines each running Ubuntu and nginx to be able to talk to one another and the outside world without interfering with the server already running on port 80 on my machine.
I made it work by adding an additional Network adapter configured as Host-only to each machine and then adding a static mapping to /etc/hosts on the client.
This way each machine can talk to the outside world (for updates, getting software, etc) and they can talk to each other both using port 80.
Only trick is I need to start the server first. There is probably some way to fix that but this is ok for now.