Errors

ciplink tells two kinds of failure apart:

• A failed tag is data in that tag's result: an error message, an error kind and, for a controller error, the CIP status. The other tags of the same call are unaffected.
• A failed call (no connection, a broken session, a bad argument) is an exception in Python, C# and C++, an Err in Rust and a status code in C. Python's exceptions derive from ciplink.PycommError; C# throws CiplinkException and C++ ciplink::Error, both carrying the status below.

Error kinds

Kind	Meaning
not_found	no such tag, member, element or bit
bad_value	the value doesn't fit the type (rejected locally or by the controller)
bad_request	a malformed request: syntax, element count, a bit of a REAL, path size
access	the tag exists but isn't accessible: External Access, AOI local tag, keyswitch or password
refused	nothing was done and it may work later: reload backoff, a state conflict, busy
table_changed	the tag table changed during the request, so the result was discarded
comm	the request or reply was lost or couldn't be parsed
device	any other controller status
other	not classified

In Python it's tag.error_kind (ciplink.ErrorKind, a str enum), in Rust error.kind (ciplink::ErrorKind), and in C#, C++ and C the lowercase name.

Call failures

Failure	Python	Rust (ciplink::Error)	C# (CiplinkException.Status)	C++ (ciplink::Error::status())	C (CiplinkStatus)
connection: refused, timed out, reset	CommError	Error::Comm	Comm	CIPLINK_STATUS_COMM	CIPLINK_STATUS_COMM
a value couldn't be encoded or decoded	DataError	Error::Data	Data	CIPLINK_STATUS_DATA	CIPLINK_STATUS_DATA
the reply couldn't be used	ResponseError	Error::Response { .. }	Response	CIPLINK_STATUS_RESPONSE	CIPLINK_STATUS_RESPONSE
the request couldn't be built	RequestError	Error::Request { .. }	Request	CIPLINK_STATUS_REQUEST	CIPLINK_STATUS_REQUEST
bad argument	ValueError	– (the types prevent it)	InvalidArgument	CIPLINK_STATUS_INVALID_ARGUMENT	CIPLINK_STATUS_INVALID_ARGUMENT
the driver kind doesn't support the call	– (no such method)	– (no such method)	Unsupported	CIPLINK_STATUS_UNSUPPORTED	CIPLINK_STATUS_UNSUPPORTED

In C, ciplink_last_error(handle) returns the message of the handle's latest failure, and ciplink_last_error(NULL) the calling thread's latest failure (use it after a constructor, a handle-less call, or with a handle shared by threads). Free the message with ciplink_string_free.

After a connection failure the driver has dropped its connection; open it again to reconnect. Failed requests are not replayed.

CIP status codes

A controller error carries the CIP general status (status) and the first extended status word (ext). Common general statuses:

Status	Meaning
0x04	path segment error (often: tag not found)
0x05	path destination unknown
0x06	partial transfer (the driver continues with fragments)
0x08	service not supported
0x0F	privilege violation
0x10	device state conflict (e.g. the keyswitch)
0x13	not enough data
0x1E	embedded service error (one service of a multiple service packet failed)
0xFF	general error; see ext (e.g. 0x2105 out of range, 0x2107 type mismatch)