There are a lot of things that can go wrong on a LAN party. If you cannot play together, those are some of the causes that I have observed over time. Each block lists some symptoms. Sadly it is hard to have a differential diagnosis in each case. So one needs to check those things one by one.
Windows has a built-in firewall. Usually when you start a game or when you
start a server in that game, a pop-up will open. There you have to decide
whether you want to allow the outgoing connection. The pop-up might open under
the full-screen game. Therefore one has to
Tab out of the game to see this.
Other security programs can have a firewall installed as well. Those do not necessarily notify you with a pop-up window but via some different way.
One way to deal with this is to disable the firewall. Those personal firewalls are there to protect you again certain attacks. And when you have lots of foreign computers in your personal network (LAN party), then you want the protection against worms and other nasty things. Therefore I would recommend to deal with the firewall and add exceptions for the games that you need and not completely disabling it.
- You cannot see other games on the network.
- Other games can be seen, but one cannot connect. A connection attempt will time out after a while (like a minute).
Different game versions
Games occasionally get updates. Those updates are so rare that it is a special thing to have the updated version. Usually these get installed when you use the online mode. The game will connect to the server and download a patch or update.
If you have players on the network which just have installed the game via CD or DVD, they still have the old version. In Command & Conquer: Generals everybody needs to connect to the online servers in order to get the update in case anyone has done so. In Crysis one has to download the updates from the website and successively install the three updates.
Game versions bought via a platform like Steam or Origin usually get updated via this platform -- that is part of their value proposition. My version of Crysis bought over Origin does not update itself, though.
Every game has a different way of showing the version number, one has to click around in the various menus to see it.
- Other games cannot be seen in the lobby.
- If somebody else cannot see the game either, let that person host the game. If you can see that game, you two have the same version.
- The game actually tells you that the versions do not match.
- Connections fail directly without any timeouts.
Virtual LAN adapters
Software packages for virtual private LANs (VPN) like Hamachi or Tunngle create a virtual LAN adapter. Virtualization packages like VirtualBox also create those adapters to communicate with the virtual machine. In any case the priority of those adapters in Windows might be set in an unintended way.
The game could broadcast and search on one of the adapters only. This way you will not see any of the games and people will not see your games.
- You do not see any games at all, nobody sees your games.
There might be cases where the game is installed with the same license key. Sure, if you just share the license key with somebody else, this will eventually happen. That is not intended, you are supposed to buy the game yourself.
This can still happen in a subtle way: Crysis when bought over Origin will install the game with a fixed CD-key as the installer used there is just the CD version. Therefore the game is installed once with the key. A guest who owns the Crysis game on Origin logs in with their account. The game is still installed with my key, we cannot play that together. The solution is to uninstall Crysis and re-install from their account. This is a bad mixture of CD-key and download-based platform. Still it took a bit to figure this one out.
- The game tells you that the keys are in use already.
- All buildings explode at the beginning of the game (Command & Conquer).