MQTT 5.0 (OASIS)

1. Structure of a control packet

   Fixed header, variable header and payload of MQTT control packets.

2. CONNECT

   Client ID, clean start, keep alive, will message and properties.

3. PUBLISH

   Topic name, QoS, retain flag, DUP and payload.

4. SUBSCRIBE

   Topic filters and subscription options.

5. Session state

   Session lifetime and state kept by client and server.

6. Quality of Service levels and flows

   QoS 0, 1 and 2 delivery flows.

7. Topic names and topic filters

   Topic levels and wildcards + and #, shared subscriptions.

8. Flow control and request/response

   Receive Maximum and request/response with response topic.

9. Enhanced authentication

   AUTH packet exchange for challenge-response methods.

10. Handling errors

    Reason codes and protocol error handling.

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