BACnet error, reject and abort codes

Updated 7 November 2026

Short answer

When a read or write fails, the device answers with an Error (class + code), a Reject or an Abort. Each is a number. Here is what every one means, with notes on the ones you will actually see. Examples: 2 = property.

Looking for a number but not sure which list it belongs to? Use the BACnet number lookup, which searches every table at once.

Error classes (8)

Number	Error class	Notes
0	device
1	object
2	property	Most failed reads and writes are in this class.
3	resources
4	security
5	services
6	vt
7	communication

Error codes (229)

Number	Error code	Notes
0	other	A catch-all: the device refused but gave no specific reason.
1	authentication-failed (newer)
2	configuration-in-progress
3	device-busy	The device is busy; try again shortly.
4	dynamic-creation-not-supported
5	file-access-denied
6	incompatible-security-levels (newer)
7	inconsistent-parameters
8	inconsistent-selection-criterion
9	invalid-data-type	Wrong data type, e.g. a Real written to a binary point, or Unsigned where Enumerated is expected.
10	invalid-file-access-method
11	invalid-file-start-position
12	invalid-operator-name (newer)
13	invalid-parameter-data-type
14	invalid-time-stamp
15	key-generation-error (newer)
16	missing-required-parameter
17	no-objects-of-specified-type
18	no-space-for-object
19	no-space-to-add-list-element
20	no-space-to-write-property
21	no-vt-sessions-available
22	property-is-not-a-list
23	object-deletion-not-permitted
24	object-identifier-already-exists
25	operational-problem
26	password-failure	The device wants a password for this service (often DeviceCommunicationControl or ReinitializeDevice).
27	read-access-denied	The device will not let you read this property.
28	security-not-supported (newer)
29	service-request-denied	The device refused the request as a whole, often because of a lock or its current state.
30	timeout	The device timed out handling the request (often while talking to a sub-network).
31	unknown-object	That object type and instance do not exist on this device. Check the instance number and the device.
32	unknown-property	The object exists but does not have that property.
34	unknown-vt-class
35	unknown-vt-session
36	unsupported-object-type
37	value-out-of-range	The value is outside the object's limits, e.g. a setpoint min/max or a state that does not exist.
38	vt-session-already-closed
39	vt-session-termination-failure
40	write-access-denied	The property is read-only, or the device blocks writes (local mode, hand/off/auto switch, lock).
41	character-set-not-supported
42	invalid-array-index	The array index does not exist, e.g. priority 17 or a state number past Number_Of_States.
43	cov-subscription-failed
44	not-cov-property
45	optional-functionality-not-supported
46	invalid-configuration-data
47	datatype-not-supported
48	duplicate-name
49	duplicate-object-id
50	property-is-not-an-array	An array index was given for a property that is not an array.
51	abort-buffer-overflow
52	abort-invalid-apdu-in-this-state
53	abort-preempted-by-higher-priority-task
54	abort-segmentation-not-supported
55	abort-proprietary
56	abort-other
57	invalid-tag
58	network-down
59	reject-buffer-overflow
60	reject-inconsistent-parameters
61	reject-invalid-parameter-data-type
62	reject-invalid-tag
63	reject-missing-required-parameter
64	reject-parameter-out-of-range
65	reject-too-many-arguments
66	reject-undefined-enumeration
67	reject-unrecognized-service
68	reject-proprietary
69	reject-other
70	unknown-device
71	unknown-route
72	value-not-initialized
73	invalid-event-state
74	no-alarm-configured
75	log-buffer-full
76	logged-value-purged
77	no-property-specified
78	not-configured-for-triggered-logging
79	unknown-subscription
80	parameter-out-of-range
81	list-element-not-found
82	busy
83	communication-disabled
84	success
85	access-denied
86	bad-destination-address
87	bad-destination-device-id
88	bad-signature
89	bad-source-address
90	bad-timestamp
91	cannot-use-key
92	cannot-verify-message-id
93	correct-key-revision
94	destination-device-id-required
95	duplicate-message
96	encryption-not-configured
97	encryption-required
98	incorrect-key
99	invalid-key-data
100	key-update-in-progress
101	malformed-message
102	not-key-server
103	security-not-configured
104	source-security-required
105	too-many-keys
106	unknown-authentication-type
107	unknown-key
108	unknown-key-revision
109	unknown-source-message
110	not-router-to-dnet
111	router-busy
112	unknown-network-message
113	message-too-long
114	security-error
115	addressing-error
116	write-bdt-failed
117	read-bdt-failed
118	register-foreign-device-failed
119	read-fdt-failed
120	delete-fdt-entry-failed
121	distribute-broadcast-failed
122	unknown-file-size
123	abort-apdu-too-long
124	abort-application-exceeded-reply-time
125	abort-out-of-resources
126	abort-tsm-timeout
127	abort-window-size-out-of-range
128	file-full
129	inconsistent-configuration
130	inconsistent-object-type
131	internal-error
132	not-configured
133	out-of-memory
134	value-too-long
135	abort-insufficient-security
136	abort-security-error
137	duplicate-entry
138	invalid-value-in-this-state
139	invalid-operation-in-this-state (newer)
140	list-item-not-numbered
141	list-item-not-timestamped
142	invalid-data-encoding
143	bvlc-function-unknown
144	bvlc-proprietary-function-unknown
145	header-encoding-error
146	header-not-understood
147	message-incomplete
148	not-a-bacnet-sc-hub
149	payload-expected
150	unexpected-data
151	node-duplicate-vmac
152	http-unexpected-response-code
153	http-no-upgrade
154	http-resource-not-local
155	http-proxy-authentication-failed
156	http-response-timeout
157	http-response-syntax-error
158	http-response-value-error
159	http-response-missing-header
160	http-websocket-header-error
161	http-upgrade-required
162	http-upgrade-error
163	http-temporary-unavailable
164	http-not-a-server
165	http-error
166	websocket-scheme-not-supported
167	websocket-unknown-control-message
168	websocket-close-error
169	websocket-closed-by-peer
170	websocket-endpoint-leaves
171	websocket-protocol-error
172	websocket-data-not-accepted
173	websocket-closed-abnormally
174	websocket-data-inconsistent
175	websocket-data-against-policy
176	websocket-frame-too-long
177	websocket-extension-missing
178	websocket-request-unavailable
179	websocket-error
180	tls-client-certificate-error
181	tls-server-certificate-error
182	tls-client-authentication-failed
183	tls-server-authentication-failed
184	tls-client-certificate-expired
185	tls-server-certificate-expired
186	tls-client-certificate-revoked
187	tls-server-certificate-revoked
188	tls-error
189	dns-unavailable
190	dns-name-resolution-failed
191	dns-resolver-failure
192	dns-error
193	tcp-connect-timeout
194	tcp-connection-refused
195	tcp-closed-by-local
196	tcp-closed-other
197	tcp-error
198	ip-address-not-reachable
199	ip-error
200	certificate-expired (newer)
201	certificate-invalid (newer)
202	certificate-malformed (newer)
203	certificate-revoked (newer)
204	unknown-security-key (newer)
205	referenced-port-in-error (newer)
206	not-enabled (newer)
207	adjust-scope-required (newer)
208	auth-scope-required (newer)
209	bind-scope-required (newer)
210	config-scope-required (newer)
211	control-scope-required (newer)
212	extended-scope-required (newer)
213	incorrect-client (newer)
214	install-scope-required (newer)
215	insufficient-scope (newer)
216	no-default-scope (newer)
217	no-policy (newer)
218	revoked-token (newer)
219	override-scope-required (newer)
220	inactive-token (newer)
221	unknown-audience (newer)
222	unknown-client (newer)
223	unknown-scope (newer)
224	view-scope-required (newer)
225	incorrect-audience (newer)
226	incorrect-client-origin (newer)
227	invalid-array-size (newer)
228	incorrect-issuer (newer)
229	invalid-token (newer)

Reject reasons (11)

Number	Reject reason	Notes
0	other
1	buffer-overflow
2	inconsistent-parameters
3	invalid-parameter-data-type	A parameter in the request had the wrong data type.
4	invalid-tag
5	missing-required-parameter
6	parameter-out-of-range	A parameter in the request was out of range.
7	too-many-arguments
8	undefined-enumeration
9	unrecognized-service	The device does not support that service, e.g. ReadPropertyMultiple. Read one property at a time.
10	invalid-data-encoding (newer)

Abort reasons (12)

Number	Abort reason	Notes
0	other
1	buffer-overflow	The request or reply did not fit the device's buffer.
2	invalid-apdu-in-this-state
3	preempted-by-higher-priority-task
4	segmentation-not-supported	The reply was too big for one packet and the device cannot split it. Ask for fewer properties at once.
5	security-error
6	insufficient-security
7	window-size-out-of-range
8	application-exceeded-reply-time
9	out-of-resources
10	tsm-timeout
11	apdu-too-long

Values come from the open-source bacnet-stack 1.6.1 (bacenum.h), which follows ANSI/ASHRAE Standard 135, and were cross-checked one by one against two other independent BACnet stacks (bacpypes and @bacnet-js/client). Entries marked (newer) are in bacnet-stack only, because the other two stacks predate them. Numbers 0-255 (and the higher ASHRAE ranges) are standard; vendors may use proprietary numbers above them.

More BACnet reference

Easy BACnet reads these values straight off the device from an Android phone and shows them as words, not numbers.