MQTT publisher

Publishes every incoming EventData record as a message to an MQTT topic. Use it to send events or telemetry to an MQTT broker.

Pins

Pin	Kind	Types	Description
Input	input	Viaducta.Plugins.Event.Types.EventData	Record to publish.

The plugin has no output pin; it ends its branch of the flow.

Configuration

Field	Type	Default	Description
Topic	string (max 255)		Required. Topic to publish to.
ClientId	string		MQTT client id. Empty: a random id at every start. A fixed id must be unique on the broker: two clients with the same id disconnect each other.
Host	string		Required. Broker host name or IP for TCP. With WebsocketConnection the full WebSocket URI (for example ws://broker:8080/mqtt).
Port	integer (1-65535)	1883	Broker port for TCP. Ignored with WebsocketConnection.
Username	string (max 256)		User name. Credentials are sent when Username is set.
Password	password (max 256)		Password.
WebsocketConnection	boolean	false	true: connect over WebSocket, Host is the URI.
UseMqtt5	boolean	false	true: MQTT 5.0, false: MQTT 3.1.1.
UseRetainFlag	boolean	false	true: messages are published with the Retain flag.
QoS	dropdown: 0 QoS0 (At most once), 1 QoS1 (At least once), 2 QoS2 (Exactly once)	0	Quality of service of published messages.

Behaviour

• The connection is opened at flow start. An empty Host or Topic, an invalid QoS or a refused or failed first connect stops the flow with an unrecoverable error. After that, a lost connection is reconnected in the background (after 1 s, doubling up to 30 s) and logged as warnings. The plugin keeps the flow running (KeepAlive) and disconnects when the flow stops.
• For every record a message is published to Topic with QoS, UseRetainFlag and EventData.Data as the body (empty when null), and the plugin waits for the publish result.
• With UseMqtt5 also: DataContentType → content type, ReplyTo → response topic, Headers → user properties. With MQTT 3.1.1 these are not sent.
• While the client is disconnected, or when the publish fails or is refused, the record fails with a recoverable error.

Notes

• EventData.Channel is ignored: the topic is always Topic. Id, Source, Type, Subject and Time are not sent.
• No TLS options for TCP connections; use a wss:// URI with WebsocketConnection for encryption.
• Keep secrets in expression settings, e.g. "Password": "=Secrets.MqttPassword".

Example

{ "Topic": "plant/line1/status", "Host": "mqtt.local", "Port": 1883, "QoS": 1, "UseMqtt5": true }

Timer → Script (builds EventData with a UTF-8 JSON Data) → MQTT publisher