IBH Link UA:MQTT Description

IBH Link UA: MQTT Function

This page summarizes the MQTT functionality of the IBH OPC UA Server/Client.

Overview

Supports MQTT publish and subscribe Multiple parallel connections to different brokers Configuration via ibhlinkua-mqtt.xml Web interface for configuration management and diagnostics Supports JSON and Sparkplug B Includes TLS, certificates, buffering, and persistent storage

Web Interface

The MQTT section allows:

Upload / download configuration Restart connections Delete configuration View diagnostics (broker, client ID, status)

Basic Concept

Publish: OPC UA → MQTT Subscribe: MQTT → OPC UA Structure defined via XML configuration

Communication Modes

JSON (Standard)

OPC UA values are sent as JSON Incoming JSON is parsed into variables Supports structures and arrays

Sparkplug B

Uses protobuf encoding Supports standard Sparkplug topics (DBIRTH, DDATA, etc.) Automatic birth messages on connect Rebirth supported

Connection Configuration

Defined in XML:

Broker address, client ID Authentication (username/password) TLS (CA, client certificate, private key) Last will message Auto reconnect Proxy support Message buffering and persistence

Security

TLS with certificates supported Optional server certificate validation PSK supported (if configured)

Buffering

Controlled via maxBufferedMessages Enables offline buffering Persistent storage via PersistDir

Cloud Support

Azure IoT Hub

Uses connection string Only one topic per hub

AWS IoT

Certificate-based authentication

Topics

Defined under Publish / Subscribe.

Key parameters:

qos (0–2) retain trigger_mode (rising_edge, falling_edge, value_change) status_var deadband

Data Types

Supported:

Numeric types (Int, UInt, Float, Double) Boolean, String, DateTime Arrays and structured data

Runtime Behavior

Subscribe

Parses incoming data (JSON / Sparkplug) Writes values into OPC UA variables Errors reflected in status

Publish

Sends values on change or trigger Uses configured QoS and retain Sparkplug generates birth/data messages

Operation & Diagnostics

Typical workflow:

Upload configuration Restart connections Check status

For troubleshooting:

Broker address Client ID Connection status XML configuration Certificates Topics and triggers