BACnet - A Data Communication Protocol for Building Automation and Control Networks - see bacnet.org. This BACnet library provides a BACnet application layer and network layer written in Python for daemons, scripting, and graphical interfaces.
Excellent ever-evolving library for implementing BACnet applications. Well maintained and supported with a growing library of samples.
Very cool stack - cleverly engineered, easy to extend, debug and support. Kudos!