Listen on a port other than 8080

[artyuum]

The port 8080 might be already taken by another service. The script should be able to automatically detect this and listen on another port. Or the end-user might specify a different port to the script (e.g. --port 3000)

[artyuum]

Spotify doesn't seem to work with wildcards for the redirect_uri parameter (e.g. localhost:*). One solution can be to register dozens of redirect_uri having a different port each, hoping that at least one of them is not already taken when running the script.