Minecraft server opened twice. Oh no right?

Do some work on the server once, and then you want to stop it to upload files.
You can quickly enter / stop in the console of the new server and upload your files.

A little later you start the server, but then you notice that the server is open twice. Auto start…
Well, what happens if you accidentally have a Minecraft server open twice at the same time?

A server can actually only be started once, since the port can only be used once. The console message "Can't bind the port" should appear on the second server, as a server is already running on it.

DeFakto: Nothing happens, only one server is started correctly.