Hello,
I think about buying the game and just found this on the GOG page:
https://support.gog.com/hc/en-us/articles/18307455486237-The-Planet-Crafter-Multiplayer-setup-instructions?product=gog&_gl=1*1r1nv27*_gcl_au*MTY1OTEyNjE5Ni4xNzIwODkyNzE0

Is it possible to play with friends via LAN? So no internet connection required, just connect two computers (offline) and play multiplayer?

Thanks for your answers.

I have not been able to do it. Spent half day digging into port forwarding articles and searching for answers and still nothing. I did everything as in the instructions but the joining side only gets a black screen.
I have forwarded the port in the router and also set up a firewall exception but right now i have no idea what to do.

Edit: I also own Re:Volt and it also uses LAN for multiplayer. I have no problems launching multiplayers there. So what i did - i set up a multiplayer Re:Volt game and on both computers and i used command prompt to fetch the used ip address information ( i used netstat -aon command). I went through the ports and tried to understand which could be used for the multiplayer and then set that up in planetcrafter. And guess what - it did not work.
There is probably something else required for it to work and i hope they implement a working option in the game.

Thank you very much for that information. I'm really disappointed to read this.

Good news. After 3 days of research i stumbled upon cases where people use VPN tools.
So i tried RadminVPN and just after 5 minutues i had 3 laptops connected in one VPN and all of them able to join one game. Just download radmin VPN, register a new network and join the PCs you need.

A few things though:
* by default windows defender firewall blocks the game from accessing internet. It throws a pop-up when you launch jour first map. Be sure to do it.
* When joining a game you must specify the ip address that radmin server provides not your original
* and just to voice my opinion - it certainly should not be like this. The game itself should provide an easy way to connect to multiplayer

I think thats it. The coop certainly did not work with my network and router settings, port forwards and what not but it cleanely connencted using Radmin and with no changes to my network config.

Great, thank you very much for that information and the good news. Although I'm absolutely with you: " it certainly should not be like this. The game itself should provide an easy way to connect to multiplayer"

So just to be sure. By using RadminVPN you can play multiplayer and you don't have to be connected to the internet at any time?

No this will not work offline. Radmin vpn is a service that is hosted by a corporation and it is done via internet.

Ok, thanks again for that information.
I hope they'll provide a possible way to play multiplayer without internet.

I don't think you need internet access to play this game with other players in the same LAN. You can just give the local IP address of the server to connect to it with the client.
For me this works. But the LAN has also internet access over the router, so I can't be 100% sure it works without internet.

Thank you for that information. It would be really great to know if LAN multiplayer definitely works without internet connection.

For me the situation is like this: 3 laptops and all of them connected to a router with wifi.
Should be working right? The description says - just write your local ip when joining and make sure the port is open as well.

The reality: with so much security layers i'm not even sure which one is blocking the connection:
* windows defender
* router firewall
* antivirus software
* something else?

I was not able to figure out even by turning off router firewall and making firewall exception on my laptop. That is why i used radmin VPN which worked like a charm.

True, i have not tested a literal LAN - laptops connected to router via cable. But due to the router location in my house it would be a pain and i don't even want to try.

@Mc_Fox
That being said - the game is fun in single player as well. If you would want to play alone - take it.
And then you can join the multiplayer setup fun with the rest of us.

I take it there's still been no advancement in this area? Still getting black screen.
Not that invested that wanna fiddle with VPN.

For ze people of ze future: what worked for me in terms of being able to host was port forwarding port 7777 in router settings.