OPC UA -> MQTT Gateway client

The purpose of this client software is to allow the transfer of OPC UA node value data to a target MQTT broker.

I made it as an assignment for the class "network programming" at my school Seinäjoki University of Applied Sciences.

Dependencies

• Compiler that supports C++11
• Qt 5.5
• FreeOpcUa library
  • Boost libraries
• Mosquitto library
  • C-Ares
  • PThread
  • OpenSSL

I personally used Qt 5.5 & MinGW32 4.9.2 while developing this and I only provide compiled library files for MinGW32 in this repository. Compiling & linking on linux shouldn't be an issue but you will probably struggle if you want to compile and link some of those libraries under Windows with MSVC.

Repository structure

• client_qt_project: This folder contains the source code of the client & Qt Creator project files.
• images: Contains images related to the gateway client project.
• libraries: This folder contains pre-compiled Windows library files for FreeOpcUa/Mosquitto & include headers.

UML Diagram, clientside relations

Very rough diagram showing the interaction between the MQTT & OPC UA client objects.

1. Subscription to node data change events is made on the OpcUa-side via client GUI.
2. Node value changes.

• DataChange event function is executed in OPCUASubClient object,
• Node value is transformed into a c-string (char *) & size of data is calculated.
• MQTTClient::publish(...) is called, arguments passed are topic, node value and size in bytes.

3. Node value is published on the MQTT server.

• Topic is "ChosenMainTopic/NodeNamespace/NodeBrowseName"
• ChosenMainTopic can be changed via the client GUI.

Screenshot of client GUI

Screenshot of the Gateway client.

Screenshot showing the GUI of the client. Connected to a FreeOpcUa python server & a Mosquitto MQTT broker.