Industrial integration guide

OPC UA to MQTT Gateway

Expose selected OPC UA values as structured MQTT topics without giving the broker direct access to the control network. Sync Connect reads the server, applies the route configuration and publishes only the data the IT side needs.

Architecture.

Deploy Sync Connect at the OT/IT boundary. It opens a client connection to the OPC UA server and a separate connection to the MQTT broker, so neither endpoint needs to reach through the other network zone.

OPC UA server

Sync Connect integration layer

MQTT broker

When this route fits.

Publish PLC and SCADA values to an edge or enterprise MQTT broker.

Feed condition monitoring, dashboards or event-driven applications.

Replace one-off OPC UA polling scripts with version-controlled routes.

Configuration pattern.

This minimal pattern uses the same provider, connector and route model as the production configuration. Replace the endpoint, broker and node identifiers with values from your environment.

config.yaml

resources:
  line-metrics:
    temperature: ns=4;i=1
    pressure: ns=4;i=2

providers:
  line-opc:
    driver: opcua
    config:
      endpoint: opc.tcp://192.168.10.20:4840

connectors:
  production-mqtt:
    driver: mqtt
    config:
      broker: 192.168.20.15
    routes:
      factory/line-1/metrics:
        mode: read
        provider: line-opc
        resource: line-metrics

Node IDs, certificate policy and credentials are project-specific and must be validated against the OPC UA server and broker before commissioning.

Technical fit.

Source protocol: OPC UA over opc.tcp
Target protocol: MQTT
Data direction: Read routes; controlled write-back where required
Deployment: Linux or Windows, ARM or x86

Security and network.

Allow the gateway to reach the OPC UA endpoint; do not expose the PLC network to the broker.
Use certificate trust lists and an OPC UA account limited to the required nodes.
Use authenticated, encrypted MQTT and restrict the client to its assigned topic prefix.
Synchronize time across the server, gateway and broker so event timestamps remain comparable.

Failure and recovery behaviour.

OPC UA unavailable

Treat loss of source quality as a separate state from a valid zero value. Test reconnect timing and the quality signal consumed by downstream systems.

Broker unavailable

Define the permitted buffer window and recovery rate during acceptance. Size it from message volume and the maximum tolerated outage.

Write-back

Keep routes read-only unless a documented setpoint use case exists. Test authorization, value ranges and the safe state independently.

Limitations and better alternatives.

The gateway does not repair an inconsistent OPC UA information model or missing source timestamps.
High-frequency waveform data may require aggregation or a purpose-built transport rather than one MQTT message per sample.
A broker topic model still needs ownership, naming and retention rules; protocol conversion alone does not provide data governance.

More integration guides.

Siemens S7 to MQTT IntegrationOpen guide Modbus TCP to MQTT GatewayOpen guide PLC to Database IntegrationOpen guide

Validate your OPC UA-to-MQTT route

Bring the server endpoint, representative node IDs, broker requirements and expected update rates. We will map the route and identify the commissioning checks.

Check technical fit