When you launch the server program, it opens specific ports (e.g., 80, 443, 8080). Then you modify your hosts file to redirect nfsworld.origin.com and world.needforspeed.com to 127.0.0.1 . The game client, thinking it’s talking to EA, happily logs you in with any username and password you type.
If you're looking to dive back in, would you prefer to focus on specific tracks, or are you interested in modding the car list once you get the server running? How to Install Need for Speed: World / Soapbox Race World nfs world offline server program for v1.9.3