Works offline. Every calculation runs on your device, no signal needed. Install the BAS Field Reference app to keep it on your phone.

Filter type to narrow the list

Type	Common reasons and what they usually mean
Error — Object	unknown-object — the object identifier doesn't exist on that device. Check the instance number and that you're talking to the right device.
Error — Property	unknown-property — the object exists but doesn't support that property. Common when a tool assumes optional properties are present.
Error — Property	write-access-denied — the property exists but isn't writable as configured. On JCI controllers this often traces back to CCT mapping.
Error — Property	value-out-of-range — the write was understood and refused on its value.
Error — Security	authentication-failed or similar — increasingly seen on BACnet/SC deployments rather than classic BACnet/IP.
Reject	buffer-overflow — the response won't fit the device's APDU size. Read fewer properties per request.
Reject	invalid-parameter-data-type — the request was built wrong, usually a client or gateway issue rather than the device.
Reject	unrecognized-service — the device doesn't implement that service at all.
Abort	buffer-overflow — same as above but the conversation was dropped entirely. Reduce the read size.
Abort	segmentation-not-supported — the response needs segmentation and the device can't do it. Request less data in one go.
Abort	application-exceeded-reply-time — device didn't answer in time. Look at trunk loading and MS/TP token rotation.

How to use it

In Wireshark, bacapp.type > 4 isolates every error, reject and abort in a capture.
Errors come from the application — the request was understood and refused.
Rejects and aborts are lower level — the request was malformed or the conversation broke down.

Go deeper

These tools come out of the book — a field reference for BACnet, Modbus, LonWorks, OPC UA and the diagnostic method that works across all of them.

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BACnet Error, Reject and Abort Reasons