How is it not clear? The first sentence in the first section is:
"I happily dove into Quake World source code." "I happily dove into Quake World source code."> QW is "Quake World" project, where Server and Client are meant to run on different machine (notice the client staring point is WinMain (in sys_win.c), whereas the Server stating point is main (also in sys_win.c)).