maximqad 

The engine's net_ws transport layer — the code that owns the UDP sockets and moves packets in and out — was replaced with stubs. They compile, they get called, they return cleanly, and they do nothing. Look at the executable's import table and there is no winsock at all: the binary has no way to open a socket even in principle.

The gutting goes past the transport. Chunks of the client that only matter when other players exist were trimmed or narrowed on the assumption that nobody would ever be online. The multiplayer menu leads nowhere.

And the disc's copy of Windows CE was built without a networking component either, so even a fully repaired game would have nothing underneath it.