Failed to Bind to Port/IP

So in my mission to get admin rights on my schools network (i have premission)

I've thought of using metasploit to make a reversetcp connect back to me.

how ever when i set up the payload it errors saying it cannot bind it IP handler.

Very annoyed i wrote a python web server script (a very simple one) and long behold same error howerver ! if i ran the python server on my LAN ip adress (10.0.0.X) it works fine and even then website "Can you see me?" Finds the port and is happy with it. But i don't understand how? if i close the webserver the port closers with it. Perhaps it's some kind of port trigger? even so how does "Can you see me ?" only find my port once the python web server is running on LAN IP ? everystrange.

Any help would be amazing thanks !