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MQTT Connector

Direction: Write Only | Type: mqtt

Publish messages to MQTT brokers with support for TLS/SSL, authentication, and Quality of Service levels.

Operations

Operation Direction Description
publish Write Publish a message to an MQTT topic

Connector Configuration

Field Required Default Description
Broker URL Yes - MQTT broker address (mqtt:// or mqtts:// for TLS)
Client ID No Auto MQTT client identifier
Username No - Broker username
Password No - Broker password
Keepalive No 60 Keepalive interval in seconds
Clean Session No true Start with a clean session
TLS No - TLS/SSL configuration (see below)
Topic No - Default publish topic (can be overridden per operation)
QoS No 0 Default Quality of Service level
Timeout No 30 Connection timeout in seconds
Retain No false Retain messages on the broker

TLS/SSL Configuration

For brokers that require encrypted connections (mqtts://):

json

{
  "tls": {
    "enabled": true,
    "ca_certs": "/path/to/ca-cert.pem",
    "certfile": "/path/to/client-cert.pem",
    "keyfile": "/path/to/client-key.pem",
    "cert_reqs": "required",
    "tls_version": "tlsv1.2"
  }
}
Field Default Options
enabled false Enable TLS/SSL
ca_certs - CA certificate file for server validation
certfile - Client certificate for mutual TLS
keyfile - Client private key for mutual TLS
cert_reqs required none, optional, required
tls_version tlsv1.2 tlsv1.1, tlsv1.2, tlsv1.3

Quality of Service (QoS)

Level Delivery Description
0 At most once Fire and forget: fastest, no acknowledgment
1 At least once Broker acknowledges receipt; may deliver duplicates
2 Exactly once Four-step handshake guarantees single delivery (slowest)

Per-Operation Configuration

When using an MQTT connector in a flow node:

Field Required Description
Topic Yes MQTT topic to publish to (supports Jinja2)
QoS No Override connector default QoS
Retain No Override connector default retain flag
Payload No Message payload (defaults to event payload as JSON)
Timeout No Override connector default timeout

Output

The full event payload is published to the configured topic as the message body. The flow step records the standardized result:

json

{
  "status": "completed",
  "data": {
    "status": "published",
    "broker": "mqtts://broker.example.com:8883",
    "topic": "events/device-42/telemetry",
    "client_id": "contact-publisher",
    "qos": 1,
    "retain": false,
    "bytes": 64
  }
}

On a connection or publish failure the step is recorded with status error and the broker error message; it is never reported as a success when delivery did not happen.

Example

Connector Setup:

json

{
  "broker_url": "mqtts://broker.example.com:8883",
  "username": "${secrets.mqtt_user}",
  "password": "${secrets.mqtt_pass}",
  "tls": { "enabled": true, "cert_reqs": "required" },
  "qos": 1
}

Operation:

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