I'm going through some tutorials right now and I don't understand this one thing. Why do I have to open port 80 when I use HTTPS? Isn't port 443 enough?
Or is port 80 open to handle the redirect from http to https?
Best practice is to listen on http and redirect to https. But this is not mandatory.
It isn't mandatory. You can listen only for secure HTTPS connection on port 443.
Try to comment out the port 80 and it should work.