BACnet/IP Server

In Server mode inSCADA publishes its own values as one BACnet device. A client on the building automation side — an upper BMS, an operating panel, another inSCADA — connects to that device and reads the values.

The shape

Level	What it becomes
Connection	The server’s UDP endpoint (47808 is standard)
Device	The published BACnet device — one per connection
Frame	One BACnet object
Variable	That object’s Present_Value

A Present_Value has no address of its own: the frame is the object and the variable is its value.

Connection

Parameter	Default	Description
Port	47808	The UDP port to listen on
APDU Timeout (ms)	3000	100 – 60000
Retries	3	0 – 10
Announce Period (s)	—	How often it announces itself (10 – 86400, 0 = off)
Max Subscriptions	—	The total COV subscription limit
Max Subscriptions Per Subscriber	—	The per-subscriber limit

Caution

The server port must be open to incoming connections in the firewall.

Device

Parameter	Description
Device Instance	The published device’s instance number
Vendor Id	The vendor identifier (0 – 65535)
Model Name	The model name (max 64 characters)
Scan Time	The polling interval — see the note below
Scan Type	PERIODIC or FIXED_DELAY

Scan time is the ceiling on COV latency

Scan Time here is the upper bound on how long a change takes to reach a subscriber: the library has no thread of its own, so a notification goes out on the next tick, and that tick is driven by the device poll. If subscribers need to hear quickly, this has to come down.

Frame — the published object

Each frame is one BACnet object.

Parameter	Description
Object Type	The object type to publish
Object Instance	The object’s instance number
Units	An analogue object’s unit (0 – 65535)
COV Increment	The notification threshold on an analogue object
Number of States	The number of states on a multi-state object (1 – 65535)
Writable	Whether the field may write to it
Relinquish Default	The value that applies once every priority is relinquished

The object types that can be published:

Analog Input	Analog Output	Analog Value
Binary Input	Binary Output	Binary Value
Multi-state Input	Multi-state Output	Multi-state Value

Choose the COV increment deliberately

An analogue object must have one. 0 is legitimate and means “notify on every change” — but on a live analogue point that floods every subscriber continuously. Enter the amount of change that actually matters for that point.

Give a multi-state object its number of states

Without one, the object looks single-state and client-side tools show something inconsistent like “state 2 of a 1-state object”.

An object is either fed or written

An object’s value is either fed by inSCADA or written by the field — never both. Input objects publish what inSCADA writes; output objects are opened to outside writes with Writable and carry a relinquish default.

Related

• BACnet overview — objects and COV
• BACnet Client — the client role