Cannot play with my friends

[Luna]

Hi there,
I ask for help because I cannot play with one of my friends at all. We start the game and try whichever one of us host the game it doesn't change the fact that the other one cannot joing at all. The message "An error occured" appears everytime.
What can we do to solve this please...

[Is This Your Card? 69]

Mods maybe?

[Ettanin]

The game uses peer to peer, therefore the ability to host and/or join depends on the individual player's internet connection.

Do this regardless of whether you have a dedicated IPv4 address or not:
* Set Steam Networking to always share your IP address for a faster connection. This will prioritize direct connections if they are possible.

Do this ONLY if you have a dedicated (also called public) IPv4 address (either static or dynamic) AND CAN open ports on your network:
* Forward UDP ports 27014, 27015, 27016, 27017, 27018, 27019, 27020, 27021, 27022, 27023, 27024, 27025, 27026, 27027, 27028, 27029, 27030, 3478, 4379, 4380. Otherwise, direct connections would be attempted by using STUN UDP hole punching which may or may not work (depends on the router).
* Do not use "Port Triggering". Port Triggering only applies if an outgoing connection is commenced beforehand, which does not work with how most peer-to-peer games perform netcode as a host. Port Triggering is intended for protocols that require server-to-client callbacks, such as FTP. Most peer-to-peer games as a host only accept incoming connections and do not perform callback connections.
* Forwarding ports will have no effect on connections that use CGNAT or Dual Stack Lite, because incoming connections will be dropped by the ISP due to their ambiguity.

If you have a dedicated IPv4 address AND forwarded the ports (see above):
* You can host without issues for other players. They can join you without using SDR whether they have a dedicated IPv4 address or not.
* You can join any game without issues, even if the host has CGNAT or Dual Stack Lite. Steam Networking will attempt a connection reversal, which means the host connects to you instead.

If you are behind CGNAT or Dual Stack Lite or cannot open ports on your network:
* Avoid hosting unless you KNOW that the players you play with all have a dedicated IPv4 address and forwarded the ports, otherwise SDR (which is buggy) is necessary.
* Avoid joining hosts that also have CGNAT or Dual Stack Lite because this makes SDR (which is buggy) necessary.
* Playing with randoms with this kind of connection flawlessly is hard. It hinges on a lot of circumstances. Ideally, you might be better off just joining and hoping that the host did the above steps.

In case both sides (host and client) use Dual Stack Lite, make sure IPv6 use is unrestricted and unimpeded, especially on the listed ports.