MQTT

Publish a payload to a named MQTT topic so any subscribed client or device receives it instantly.

Open a persistent subscription to an MQTT topic or wildcard pattern so the agent receives all matching messages in real time.

Cancel an active subscription so the agent stops receiving messages on the specified topic pattern.

Establish an authenticated TCP or TLS session to an MQTT broker, setting client ID, keep-alive interval, and optional last-will topic.

Send a clean DISCONNECT packet to the broker and tear down the session, releasing the client slot gracefully.

Configure the Quality of Service level (0, 1, or 2) for a publish or subscribe operation to control delivery guarantees.

Publish a message with the retain flag set so new subscribers instantly receive the last known value when they connect to the topic.

Register a last-will-and-testament payload the broker automatically publishes if the client disconnects ungracefully.

Retrieve the current list of topic filters the active client is subscribed to, along with their QoS levels.

Read the last retained message stored on a specific topic without waiting for a new publish event.

Query the broker's $SYS topic tree to retrieve live metrics: connected clients, message rates, subscriptions, and uptime.

Fan a single payload out to a list of topic strings in one operation, useful when the same event must reach several partitioned consumers.

Poll or await a single inbound message on a subscribed topic and return its payload, topic string, QoS, and retain flag.

Clear a retained message from a topic by publishing a zero-byte payload with the retain flag, so future subscribers no longer receive stale data.

Verify whether the current broker session is active and return the connection state, client ID, and elapsed session time.

Map a full topic string to a short integer alias (MQTT 5.0) to reduce per-message overhead on high-frequency publish paths.

Fires when any message arrives on a subscribed topic, delivering the full payload, topic string, QoS level, and retain flag to the workflow.

Fires when a new MQTT client establishes a session with the broker, exposing the client ID, clean-session flag, and connection timestamp.

Fires when a client session ends, either cleanly or ungracefully, providing the client ID, disconnect reason code, and whether the last-will was sent.

Fires when the retained value on a monitored topic changes, delivering the old and new payloads so the agent can react to state transitions.

Fires when the numeric value in a message payload on a numeric topic exceeds or drops below a configured threshold, enabling level-based alerting.

Fires when the broker's $SYS metrics cross a monitored threshold — such as connected-client count, message rate, or queue depth — signalling infrastructure stress.

Fires when the broker publishes a client's pre-registered last-will payload following an ungraceful disconnect, indicating an unexpected device or service failure.