MQTT In

This is an enhanced version of the standard MQTT In node, designed exclusively for FlowFuse users. The node features automatic configuration upon deployment. The MQTT broker client is created automatically alongside the node configuration when added to the canvas.

Configuration Options

Server Configuration

The server is automatically configured and managed by the FlowFuse platform. All FlowFuse MQTT nodes within an instance share a single broker connection, ensuring efficient resource utilization and consistent connection management across all flows. Access control can be managed through the broker client management interface, where permissions for subscribe and publish operations can be configured.

Note: When the first node is added to the canvas, a new Team Broker User linked to the FlowFuse instance is automatically created. By default, this user has subscribe-only permissions.

Subscription Mode

The node supports two operational modes:

  • Single topic mode: Allows subscription to a fixed topic configured directly in the node settings
  • Dynamic subscription mode: Enables runtime control of subscriptions through input messages

Topic Configuration

When operating in single topic mode, specify the MQTT topic to subscribe to in the node configuration. The topic field supports MQTT wildcard patterns for flexible message routing.

Quality of Service

Select from three QoS levels:

  • Level 0: Fire-and-forget delivery
  • Level 1: At-least-once delivery
  • Level 2: Exactly-once delivery (default)

Output Format

The node can automatically detect the message format or convert it to a specific type including:

  • Buffer
  • String
  • Parsed JSON object
  • Base64 encoded string

Message Output Properties

Each received message includes the following properties:

  • msg.payload: The message content as string or buffer
  • msg.topic: The MQTT topic from which the message was received
  • msg.qos: The quality of service level (0, 1, or 2)
  • msg.retain: Boolean indicating whether the message was retained on the broker
  • msg.responseTopic: MQTT version 5 response topic for request-response patterns
  • msg.correlationData: MQTT version 5 correlation data for message tracking
  • msg.contentType: MQTT version 5 content type descriptor
  • msg.userProperties: MQTT version 5 custom user properties
  • msg.messageExpiryInterval: MQTT version 5 message expiry time in seconds

Dynamic Control Operations

When dynamic subscription mode is enabled, the node accepts control messages through the msg.action property. The following actions are supported:

Connect

Establishes connection to the MQTT broker.

msg.action = 'connect';

Disconnect

Terminates the broker connection.

msg.action = 'disconnect';

Get Subscriptions

Retrieves the list of current topic subscriptions.

msg.action = 'getSubscriptions';

Subscribe

Subscribes to one or more topics.

// Single topic
msg.action = 'subscribe';
msg.topic = 'sensors/temperature';

// Single topic with QoS
msg.action = 'subscribe';
msg.topic = { topic: 'sensors/temperature', qos: 1 };

// Multiple topics
msg.action = 'subscribe';
msg.topic = ['sensors/temperature', 'sensors/humidity'];

// Multiple topics with QoS
msg.action = 'subscribe';
msg.topic = [
  { topic: 'sensors/temperature', qos: 1 },
  { topic: 'sensors/humidity', qos: 2 }
];

Unsubscribe

Removes subscriptions from one or more topics.

// Single topic
msg.action = 'unsubscribe';
msg.topic = 'sensors/temperature';

// Multiple topics
msg.action = 'unsubscribe';
msg.topic = ['sensors/temperature', 'sensors/humidity'];

Topic Wildcard Patterns

MQTT supports two wildcard characters for flexible topic matching:

  • Plus sign (+): Single-level wildcard
  • Hash symbol (#): Multi-level wildcard

Note:* The # wildcard can only be used at the end of a topic when defining subscriptions.

Example Patterns

  • sensors/+/temperature - Receives temperature readings from all sensor locations
  • factory/# - Receives all messages published under the factory topic hierarchy
  • devices/+/status - Receives status updates from all devices
  • building/floor1/# - Receives all messages from floor 1 of the building

Version Support

This node fully supports MQTT version 5 features including response topics, correlation data, content types, user properties, message expiry intervals, and topic aliases. It maintains backward compatibility with earlier MQTT versions.