MQTT

OV Spark has a built-in MQTT client. It connects to your broker, on your network or in the cloud, and:

• publishes every inspection result as JSON, with no script at all
• publishes a heartbeat and its online status
• receives values, such as the current lot number, into variables

It supports MQTT 3.1.1 and 5, with plain TCP, TLS or mutual TLS (client certificates).

Open Integration > Data Connectors and choose MQTT.

Set it up

Setup has three steps.

1. Connect to the broker

Pick the kind of broker to fill in typical settings, which you can change:

Broker type	Typical
Plant broker (Mosquitto, HiveMQ, EMQX)	Port 1883, or 8883 with TLS
Ignition / SCADA (Ignition MQTT Distributor and similar)	Port 1883
Cloud broker (AWS IoT, Azure, HiveMQ Cloud and similar)	Port 8883 with TLS
Something else	Any MQTT 3.1.1 or 5 broker; you set every field

Setting	Notes
Address and Port	The broker's host name or IP address. Default port 1883
MQTT version	5 (default) or 3.1.1
Security	None, TLS, or Mutual TLS (client certificate). TLS without a CA certificate uses the camera's built-in trust store; mutual TLS needs a CA, a client certificate and a client key
Username and password	Leave empty if the broker allows anonymous connections
Advanced	Client ID (the camera's serial by default), keep-alive (30 s) and clean session (on)

The connection check runs a second after you stop typing: it looks up the host name, connects to the port, checks TLS and logs in, one step at a time. Settings are saved when you press Save and continue at each step, and MQTT stays off until step 3.

Use TLS across the plant network

None sends everything unencrypted, including the password. That is fine on an isolated machine network. Use TLS if the traffic crosses the plant or office network, and mutual TLS for cloud brokers that require client certificates.

2. Choose what to send

Message	Default topic	Notes
Inspection results	overview/<serial>/results	One message per production inspection, at the QoS you choose (1 by default). Summary leaves out each tool's detail; Full includes it
Heartbeat	overview/<serial>/heartbeat	Every N seconds (5 or more, or off), at QoS 0
Online status	overview/<serial>/status	A retained {"status":"online"}, and a last-will {"status":"offline"} the broker sends if the camera drops off

You can change each topic, for example to plant/line3/results.

3. Turn on MQTT

Turn MQTT on, then watch every message go out under Monitor > Topics and messages.

Results are not retained

Result messages are published with retain off, so a subscriber that connects later does not receive an old result as if it were new. To keep the last result available, publish it yourself from the camera script with retain: true, or read it from the HTTP API.

What a result message looks like

The same document is used by MQTT, the HTTP API and the camera script's onResult. A Full result, shortened:

{
  "schema_version": 1,
  "serial": "5F9FE801",
  "id": "01a17216-f035-7ec5-adae-b90b6a0868a8",
  "recipe": { "id": 3, "name": "Kit tray" },
  "trigger": { "id": 420596, "source": "plc" },
  "image": { "width": 2592, "height": 1944, "url": "/api/integration/v1/results/01a17216-f035-7ec5-adae-b90b6a0868a8/image" },
  "captured_at": "2026-10-25T08:04:28.341Z",
  "processing_ms": 82,
  "judgment": "fail",
  "pass": false,
  "not_inspected": false,
  "reason": "serial differs",
  "judgment_source": "script",
  "rules": { "judgment": "pass", "pass": true, "not_inspected": false },
  "vars": { "serial": "SN-24-118734" },
  "tools": [
    {
      "id": "01a15f8b-da07-7e42-8b3e-d3edaff79428",
      "type": "classical.barcode",
      "name": "Label",
      "plc_slot": 1,
      "judgment": "pass",
      "score": 1,
      "execute_ms": 4,
      "detail": { "decoded": true, "data": "0104012345678901", "symbology": "data_matrix" }
    }
  ],
  "metadata": {},
  "tags": [],
  "plc_inspection_id": 1234,
  "phase": "production"
}

• judgment_source says what decided the verdict: the rules, the recipe script, or script_error when the script failed
• rules is the rules' verdict, even when the script decided
• vars holds the variables the inspection saved
• image.url fetches the image over the HTTP API

The heartbeat is small:

{"schema_version":1,"serial":"5F9FE801","hostname":"line3-cam","recipe":"Kit tray","phase":"production","uptime_s":3600,"mqtt":"connected","ts":"2026-10-25T08:04:28.341Z"}

Receive values

To bring a value in, declare a variable with MQTT as its source: the topic, and for JSON the path to the field. Every inspection then saves the latest value. For anything more involved, such as picking a field out of a vendor's message or answering requests, use the camera script.

Exports come in switched off

MQTT settings travel with recipe exports, but passwords and certificates are never exported. If the source camera used credentials the target camera does not have, MQTT arrives switched off. Otherwise it keeps the source's on or off setting, so an import onto a camera that can reach an anonymous broker can start publishing straight away. Check Data Connectors after every import.

Where to go next

• Camera script, for your own topics and message formats
• Variables
• HTTP API