Pass thoses firewalls and other corporates proxy/VPN/… that block most ports. If what you build is at least partly used where user have internet access, you know this port is open. Even if 22, 8080 and all the others are closed.

Are you the one user of this OS Server side? /s

Nextcloud.

And a subsonic app. There is also another protocol available so you have quite the choice for which you prefer. Currently using Tempo.