With the recent Tailscale Funnel announcement, I briefly had my hopes up of perhaps finally being able to host one-off game sessions without asking everyone else to install clients or register accounts.
Simply give them a one-off URL that they type into their gameclient and they connect to it exactly like a public server, which I can then disable after the session.
However, it seems that Tailscale Funnel it is limited to TCP connections, for security reasons I suppose.
I then looked at ZeroTier but it seems like yet another Hamachi-clone, all participants are still required to install clients.
Is buying a VPS/opening your home internet firewall really still the only way in 2022?
I know that Steam Networking allows for p2p connections via their backbone, but it requires the game itself to have the API programmed, you cannot tunnel third-party programs through it.
I feel like this is a glaring product void that inexplicably nobody seems to have noticed? One would think that a gaming-focused company like Discord would have picked up on such a use case by now (coordinating short self-hosted gaming sessions with strangers without configuration).
The only other thing that can exist, semantically, is nat hole-punching, which unless you have very good coordination with your friends can only be done through software (and also involves a server but less so).
Maybe reconsider why you can't forward ports on your router? If the server isn't listening for connections on that port it's undistinguishable from a closed port, and if it is then it is available as a game server.