[2022] Can't connect to bros game? "a connection could not be established"

Can you confirm if UPnP is enabled in config for the host, and on the router for the host? If not using Upnp, you will need to make sure the ports are forwarded. Additionally, check firewall settings.

Originally posted by Gatekeeper019: Why do I need to do all of this to simply play a feature on the game? Game already refunded.

Using steam's inbuilt peer-to-peer has issues, and it also requires us to require the SteamSDK for all users. We have removed the requirement for this, making the game completely DRM free. This allows all users to play the game together, whether their copy is pirated, copied from someone else, or via steam or anywhere else. This means the game will survive even if our studio goes under, or steam stops operating etc...

Because of how security and routers work, unless customers "allow" an application through a firewall and router - the game is not visible. This is an important aspect of modern internet security, otherwise games and applications could cause havoc on peoples devices. UPnP slightly gets around this, but many don't like to use it (and it is often not default to on) due to the security concerns around it.

The only way around it is to do what steam does, and have a relay server do some magic to try and do "NAT punchthrough". This is extremely complicated, even for steam and games like CoD. The approach we take is the standard for many games, like Factorio, Space Engineers, Project Zomboid, Stormworks, Barotrauma.

Note that in the factorio multiplayer instructions[wiki.factorio.com] that if you do not play through steam, you don't get access to the steam SDK provided peer-to-peer or nat traversal features.

It is extremely expensive to support both the full steamSDK and maintain steam agnostic support. For most of Factorio's development, this was not supported. However, factorio is one of the best selling games on steam.

It is unfortunately not standard to provide this one click service, as there is no way to do it without fully integrating the steamSDK. This works if you are okay making your game entirely dependent on steam, or writing two completely different systems to handle those with steam and those without.

Originally posted by DigitizedSoul: Spot on!

After 5 years, the only real way to play being using a VPN is a joke.

You do not need to play via VPN.

However, you need to either:
* Port forward your router; or
* Enable UPnP

You also need to:
* allow the application through your firewall

I am not sure how VPN would help at all, in fact I think it would likely make things much worse.