Error
code
HTTP
code
Message Note
401 400 Data storage mismatch No match between configured device and
data from data memory. Check device ID.
Processing error in the process data
501 400 I/Q is not configured as DIGI‐
TAL_OUTPUT
Writing process data on I/Q is not possi‐
ble
502 400 C/Q is not configured as DIGI‐
TAL_OUTPUT
Writing process data on C/Q is not possi‐
ble
503 400 IO-Link device has no output
process data
Error in the payload
701 400 Data set incomplete
702 400 Data set not applicable The entire data set is denied
703 400 Data set combination incompati‐
ble
The entire data set is denied
8.2.2 MQTT client
The SIG350 provides a MQTT interface with JSON data format for accessing the data of
the IO-Link Master and of the connected devices. These operating instructions provide
an overview of the available messages and the access mechanisms.
8.2.2.1 General description
The MQTT (Message Queuing Telemetry Transport) protocol is an open network protocol
for machine-to-machine communication that enables the transmission of telemetric
data between devices. The built-in MQTT client allows the device to publish a specific
set of information to an MQTT broker.
Messages are published once after the device is started and then when the corre‐
sponding value is changed. However, the sending of the message does not take place
immediately, but cyclically, every 5 seconds. In addition to the payload, so-called topics
are also transmitted in the messages. This allows for mapping and hierarchical identifi‐
cation.
The data structure of the messages is in JSON format and is directly oriented on the
schema of the REST API (see "API structure", page 44).
Quality of Service cannot be configured and is set to “At most once”, i.e. messages are
only sent once without confirmation from the client or broker.
If the connection is lost, a Last Will is sent with the following message:
Table 35: Last Will message
Topic Message
EXIT “Publisher”: “Offline”
The MQTT functions are activated in the delivery state. The MQTT client can be deacti‐
vated either via the web interface or directly via the rotary switches.
8.2.2.2 Messages – topics
The following gives an overview of the available messages. The composition of the
topics is based on the REST API schema and is composed as follows:
{client head topic}/[BasePath]/[Domain]/{Parameter}
8 OPERATION
50
O P E R A T I N G I N S T R U C T I O N S | Sensor Integration Gateway - SIG350 8027834./2022-06-10 | SICK
Subject to change without notice
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