Protocol
These pages define the rules that every command and event follows. The operation pages under Management, Control, and Events assume them.
One Exchange, End to End
| Stage | What happens | Specified on |
|---|---|---|
| Address | Your application builds the reader's command and response topics from the endpoint's configuration. | Topics and Channels |
| Subscribe | Your application subscribes to the response topic, and to the event topic if the command finishes asynchronously. | Delivery and Retry Semantics |
| Publish | Your application publishes a command envelope at QoS 1. The broker's PUBACK means only that the broker received it. | Message Envelopes and Correlation, Delivery and Retry Semantics |
| Reply | The reader publishes one response with your requestId. Most commands finish with this reply; three acknowledge with code 1 and finish later. | Message Envelopes and Correlation |
| Outcome | Your application reads response.code, or waits for the event that reports the outcome. | Response Codes |
Choose a Page
| If you need to… | Read |
|---|---|
| Connect the reader to your broker, and understand its session | Connection and Session |
| Encrypt the connection, and authenticate the reader and your application | TLS and Authentication |
| Build a topic, or find which topic carries which traffic | Topics and Channels |
| Look up the topic slots of each endpoint type | Endpoints and Topic Slots |
| Build a command, recognize an event, and pair a reply with its request | Message Envelopes and Correlation |
| Handle lost and duplicate messages, retained messages, and the Last Will | Delivery and Retry Semantics |
In This Section
Connection and Session
How the reader reaches your broker, and how the connection is secured.
TLS and Authentication
Selecting MQTT_TLS, verification levels, and the certificates the reader uses.
Topics and Channels
Topic segments, topic slots, direction, and limits.
Endpoints and Topic Slots
Endpoint types, the publish-topic slot table, and per-endpoint limits.
Message Envelopes and Correlation
Command, response, and event shapes, and how to tell events apart.
Delivery and Retry Semantics
Declared QoS per message, duplicates, repeat safety, and loss.