OpenUaSim

OpenUaSim is an open source OPC UA simulation server with a desktop UI, built on Qt 6 and QUaServer.

Features

• Custom address spaces with folders, objects and typed scalar or array variables, configurable access levels, initial values and Good, Bad or Uncertain quality for testing client behavior.
• Variable simulation with sine, square, triangle, ramp, random and step waveforms, Boolean toggles, counters and value lists, with configurable timing, amplitude and offset.
• Callable OPC UA methods to reset variables or set their values, and configurable method scenarios with typed arguments, output sources and ordered variable assignments.
• Numeric limit alarms and Boolean off-normal alarms, with event notifications and client acknowledgement.
• In-memory value history accessible through HistoryRead, with configurable retention by value count and age.
• NodeSet2 companion model import, namespace export and instantiation of imported object types and standard variable types. Supported variables in imported models can use simulation, alarms and history.
• Variable icons published to clients as the standard Icon property (32×32 PNG, ImagePNG).
• opc.tcp endpoints with configurable security policies and message security modes, anonymous access, username/password and X.509 user certificate authentication, certificate trust validation and a configurable session limit.
• Local Discovery Server (LDS) registration with automatic renewal, allowing clients to find the server through FindServers.

Limitations

All enabled endpoints share one TCP port. Method scenarios currently support SET actions; delayed WAIT actions are not supported. Simulation sources produce scalar values.

Method scenarios

Create a Method with the Scenario action under a folder or object, then select it to add input and output arguments. Enter a built-in data type such as Double or UInt32[] for an array. Imported methods keep the signature defined by their model and offer the same source and action editors.

For each output, double-click its Source cell and choose a constant, an input argument, a variable or a simulation. Constants use semicolons between array elements; an empty constant uses the type's default value. Input and variable sources must match the target's underlying data type and scalar or array shape.

Use Add SET to assign a variable when the method is called. Enter its NodeId, double-click its Source cell, and use Up, Down or Enabled to control execution. Enabled assignments run in order, then output values are sampled. For example, a method can copy its first input into a setpoint variable and return that variable's updated value. A configured Bad response status performs no assignments. An unavailable source or target returns BadConfigurationError; already completed assignments are retained if a later runtime error occurs.

Simulation sources sample the existing waveform generator using elapsed time since the server's first scenario call. Project variable references retain namespace index 1; imported references use namespace URIs so model load order does not change their meaning. Scenarios are saved in project format 3; older project formats remain readable. Changing a project method's signature rebuilds the address space; changing its response sources or actions applies live.

Quick start

On first launch OpenUaSim opens a sample project: a FactoryLine_01 folder with a motor, a conveyor, a pump and a tank, each holding simulated variables. The sample includes endpoints with and without message security; the steps below use the unsecured endpoint with anonymous access.

1. Choose Server → Start Server.
2. Connect any OPC UA client — for example OpenUaExplorer — to opc.tcp://localhost:48400 with security None and anonymous login.
3. Browse Objects/FactoryLine_01 and subscribe to a variable to watch it change.

System requirements

The application runs on:

• Windows 10 or later (x64)
• macOS 13 or later (Apple silicon)
• Linux — x86-64, glibc 2.28 or newer

Linux binaries require compatible Qt and OpenSSL libraries. Compatibility with glibc 2.28 requires a build using a compatible toolchain and dependencies; see BUILDING.md.

Building

Requirements:

• CMake 3.22 or newer and a C++17 compiler.
• Qt 6.9 or newer (Core, Gui, Network, Widgets, Svg; Test for the test suite).
• Qt LinguistTools for the application translations.
• Git and Python 3 — QUaServer and open62541 are fetched and built during configuration.
• OpenSSL 3 for encryption (on by default). On Windows the OpenSSL from the Qt installer is found automatically.

The build is continuously tested on:

• Ubuntu Linux (latest GitHub runner)
• Windows (latest GitHub runner, MSVC)
• macOS (latest GitHub runner, Apple silicon)

The helper scripts prepare the dependencies and build a Release version with Ninja:

# Windows (PowerShell)
.\build.ps1
.\build.ps1 -Tests
.\build.ps1 -InstallPrefix "D:\Apps\OpenUaSim"

# Linux and macOS (Bash)
bash build.sh
bash build.sh --tests
bash build.sh --install="$HOME/.local"

Use -Help or --help for options. See BUILDING.md for dependency installation, build directories and installation details.

Alternatively, configure, build and run the tests with CMake, pointing CMAKE_PREFIX_PATH at your Qt kit. Omit -DOUASIM_BUILD_TESTS=ON to build without tests.

cmake -S src -B build -DCMAKE_PREFIX_PATH=/path/to/Qt/6.9/<kit> -DOUASIM_BUILD_TESTS=ON
cmake --build build --parallel
ctest --test-dir build --output-on-failure

Options:

Option	Default	Description
OUASIM_BUILD_TESTS	OFF	Build the Qt Test suites (needs Qt Test).
OUASIM_WITH_ENCRYPTION	ON	Build QUaServer with OpenSSL 3 encryption.
OUASIM_DEPLOY_RUNTIME	ON	Deploy Qt/OpenSSL on Windows/macOS install.
OUASIM_QUASERVER_TAG	master	QUaServer git tag or commit to fetch.

Feedback

Found a bug or missing a feature? Open an issue in the issue tracker. Pull requests are welcome.

MIT License

Copyright (c) 2026 Alexandr Ananev. See LICENSE for the full text.