BACnet was designed to allow communication of building automation and control systems for applications such as heating, ventilating, and air-conditioning control (HVAC), lighting control, access control, and fire detection systems and their associated equipment. The BACnet protocol provides mechanisms for computerized building automation devices to exchange information, regardless of the particular building service they perform. From Wikipedia
Default port: 47808
PORT STATE SERVICE47808/udp open BACNet -- Building Automation and Control NetworksEnumerate
nmap --script bacnet-info --script-args full=yes -sV -p 47808 <IP>
This script does not attempt to join a BACnet network as a foreign device, it simply sends BACnet requests directly to an IP addressable device.