Wikipedia
OpenPlay
OpenPlay is the name of an open source cross-platform networking library created by Apple Inc. OpenPlay compiles and runs on the Mac OS, Mac OS X, Windows and Linux operating systems. OpenPlay is a high-level networking solution for game applications. It is known for its abstraction of game and player on top of an automatically managed networking core.
As of version 2.0, it includes the NetSprockets API from Mac OS 9. NetSprockets was a subset of Apple's now obsolete Game Sprockets.