Serious Sam 3: BFE via LAN without the Steam client active, you typically need a Steam emulator to bypass the game's built-in DRM and networking requirements. The most common and reliable method involves using a tool like the Goldberg Steam Emulator
Click LAN Games (not Internet).
If the built-in multiplayer feature does not work or is not convenient, a third-party tool like Hamachi can be used to create a virtual LAN network. Here's how: how to play serious sam 3 multiplayer lan without steam
If you own a legitimate Steam copy but want to play purely over LAN without logging into Steam: Serious Sam 3: BFE via LAN without the
Third-party tools can trick the game into seeing other computers as if they are on a local network, often bypassing the need for an active Steam connection to find lobbies. LAN parties without internet People who hate forced