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the publisher to newly connected subscribers. One possibility to prevent sending of these
messages by the broker is to send an empty message (0 bytes) to the broker.
● QoS
You use the "Quality of Service" parameter to specify the transfer performance of the
messages for this topic:
– QoS 0
– QoS 1
– QoS 2
When a connection is aborted, the data frames are buffered for QoS 1 and QoS 2. See
also the section "Connection abort" below.
● User data format
You use this button to open the User data editor to specify the format of the transferred
user data. For a description, see section User data format (Page 89).
● Data point assignment
Using the drop-down list, you assign the configured data points to a previously created
topic or a group. For a description, see section Data point assignment (Page 94).
You assign the transferred user data to the topics in the data point configuration.
● Delete
By clicking the button, the topic of the respective row is deleted.
Note
Delete
Note that if you accidentally delete a topic or a group, you cannot undo the deletion.
SIMATIC CC7
Operating Instructions, 10/2019, C79000-G8976-C503-02
Transfer no more than once
The device sends the topic once to the broker. The device does not expect an
acknowledgment. If the topic is not received by the broker, it is lost.
Transfer at least once
The device sends the topic to the broker until it receives a PUBACK packet as
acknowledgment from the broker.
Transfer exactly once
The device sends the topic and waits until it receives the two-step acknowledgment
from the broker as specified.
This version represents the highest level of quality, but it is also associated with the
highest administrative burden for the client as well as the server.
Configuration
4.9 Cloud configuration
87
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