BACnet / BACnet-IP / BACnet MS/TP / BACnet-SC
BACnet is a building automation and control protocol used for HVAC, lighting, occupancy, alarms and supervisory integration. BACnet/IP, MS/TP and Secure Connect use different datalinks. Select the deployed datalink and device profile before preparing a network or wiring schedule.
Scope: Select BACnet/IP, BACnet/SC or BACnet MS/TP datalink
protocol · Catalog reviewed 2026-09-27
ASHRAE 135 / ISO 16484-5
Infrastructure Requirements
- Agree the BACnet objects and access permissions with the building-controls integrator. Select the datalink and network numbering
- for IP broadcast across subnets, design BBMD/foreign-device registration or a BACnet routing solution. SC additionally needs certificate trust and the configured hub URI
- MS/TP needs serial wiring and commissioning.
Network & Physical Requirements
| Port / allocation | Transport | Connection / signal flow | Feature and requirement | Evidence |
|---|---|---|---|---|
| 47808 (default) | UDP | BACnet/IP device → BACnet/IP peer / BBMD | Optional · BACnet/IP BACnet/IP messages BACnet/IP; BASrouter documented default and configurable listener Configure actual BACnet network/port. BBMD and foreign-device registration are separate routing/broadcast functions. | Source checked 2026-09-27 6.3 BACnet/IP Parameters: UDP PortUM-BASRTB03-AA9, FW3.0+ |
| Configured | TCP | SC node → SC hub | Optional · BACnet/SC BACnet/SC secure WebSocket connection BACnet/SC hub URI Use the actual wss URI port and mutual-certificate trust. TCP 47808 is not a universal SC default. | Source checked 2026-09-27 Addendum 135-2016bj, YY.7.2 WebSocket URIs and YY.7.4 Connection Security |
Physical, link and configuration requirements
physical · Optional · MS/TP
MS/TP uses an EIA-485 serial bus with token passing; configure baud, MAC, Max Master, topology and termination.
BACnet MS/TP EIA-485 bus; BASrouter commissioning example
Match baud and unique MAC addresses; set Max Master appropriately and follow device bias/termination/common-conductor requirements.
Gotchas & IT Notes
- ⚠Do not write one generic firewall line for "BACnet". Identify the datalink first: BACnet/IP, BACnet MS/TP, BACnet/SC, or a gateway exposing BACnet objects from another protocol.
- ⚠Classic BACnet/IP is normally UDP 47808 / 0xBAC0. IANA also registers TCP 47808, but that does not mean every classic BACnet/IP device needs TCP opened. Add TCP only when BACnet/SC or endpoint documentation actually requires it.
- ⚠Broadcast is the classic BACnet/IP routing trap. Local discovery and broadcast management collide with segmented enterprise networks unless BBMD, foreign-device registration, static routing, or a Secure Connect architecture is designed up front.
- ⚠Do not expose UDP 47808 or TCP 47808 broadly or to the public internet. Treat BACnet as an internal building-control/management-plane protocol and constrain it with VLANs, ACLs, firewalls, and named integration hosts.
- ⚠BACnet/SC is the better security direction, but it is not a checkbox. It introduces certificate authority, trust-store, DNS/URI, TLS policy, hub/failover, and operational ownership requirements that must be assigned in the scope.