Any way to test multiplayer game online without opening port on router?

I can’t open ports on my stupid router.

afaik epic online services has support for nat and port forwarding.
this works for client to server, but also for p2p scenarios https://dev.epicgames.com/docs/game-services/p-2-p
(they are different though)
you can also use another tool to forward a port, like ssh, hamachi, nomachine, etc.

Easiest is probably to pay a few dollars and rent a server online. Azure is pretty good for Windows servers. Google Cloud is great for Linux servers.
If you’ve never used a cloud before, you’ll need to learn some basics of online systems:

  • vpc – the “network” of your online “machines” (only one in this case)
  • volume – the “hard disk” if your online “machine,” which can be detached and re-used for another machine even when you delete/turn off one machine
  • VM/instance/node – the “machine” in question, given some amount of CPU and RAM resources. This will typically have the ability to be given a public network address, and can listen on whatever ports it wants.

Typically you can get away with some kind of instance that costs less than a dollar an hour, unless you need to actually build/develop on the machine, in which case you need more RAM, CPU, and maybe even a virtual GPU.
You’ll also pay a couple of bucks a month to keep the volume (hard drive) around if you don’t delete and re-create it each time you start a new testing machine. Typically worth it because re-installing things from scratch frequently is annoying. But if all you need is to unzip a folder with your server and assets, maybe that’s easy enough.