How to change the http port for play framework 2.4.1?

Question

I come from a play 1.2.7 application and currently getting started with play framework 2.4.1 and scala. For a start I use the activator web ui to manage applications and the

Answer 1

Just a short note concerning the run command (tested with Play! 2.4):

At least on Windows activator run -Dhttp.port=80 does NOT work, but activator (hit enter) and then run -Dhttp.port=80 works