Should work by running python3 server.py if you have mpv installed. On Windows this means having mpv.com in your PATH or mpv-remote files all over the mpv directory.

To set a password against unauthorized LAN access or CSRF, create preferences/login containing username:password.

You can add mpv-remote specific mpv configurations, such as fs-screen=1 or force-window=yes to preferences/mpv.conf. It will be loaded and appended to mpv command line.

Open http://example:9876 on your smartphone and you will be redirected to your home directory. Navigate to media files and click to play them on your HTPC.