Adeunis RF COMFORT MQTT, Руководство пользователя

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User Guide | COMFORT SERENITY MQTT | NB-IoT / LTE-Cat-M1 53
Adeunis recommends importing 2 certificates into the product as certificates cannot
be updated remotely.
The COMFORT Serenity product does not support advanced security modes
(X509 client certificate). Therefore, the product is not compatible with AWS and
Azure servers.
Quality of Service (QoS)
Three levels of Quality of Service (QoS) determine how the MQTT protocol handles
message transmission (client-to-broker publish messages and broker-to-subscriber
messages). Subscribed clients can specify the maximum QoS level they wish to
receive.
The COMFORT Serenity product supports QoS level 1.
QoS 1 "At least once"
This level ensures that the message sent by the COMFORT Serenity product
(PUBLISH) will be received at least once. The sender retains the message until it
receives an acknowledgment (PUBACK).
After a certain period, if no acknowledgment with the corresponding message
identifier is received, the sender resends the message. The message can be sent
multiple times until a confirmation is received.
Furthermore, when the recipient receives a QoS level 1 message, it can process it
immediately before sending an acknowledgment. For example, when the broker
receives a message, it sends that message to all subscribers and then
acknowledges the message to the recipient.
Therefore, a message can be sent and received multiple times. This duplicate will
contain a DUP flag that will not be processed by the receiver. The receiver will send
an acknowledgment without considering the DUP flag.