how to force a flask web app to run on specific port in local development?

 when I execute flask run to launch the flask web app in my laptop. I usaully encoutered an error as following.

    "OSError: [WinError 10013] An attempt was made to access a socket in a way forbidden by its access permissions " 

since the windows firewall had block this port.

I can assign the port during the launch to void this issue. i assing 300 for this app.

flask run -h localhost -p 3000