I have a habit of not typing the protocol (http:// or https://) when typing an URL. Except, when I enter a port in the address line. I hit the Home key and add the protocol then. I am pretty sure I picked up this habit to work around a problem.
I just tried not supplying the protocol for a URL using a port and did not encounter a problem. Maybe I was neurotic and just imagine I needed to do it. Still, I feel relieved to drop a habit.