Hi everyone

I’d like to introduce OpenModSim, a lightweight and flexible open source Modbus TCP/RTU simulation server designed for developers, testers, and automation engineers.

If you work with PLCs, SCADA, HMIs, or any Modbus-enabled systems, this tool helps you simulate real devices without needing physical hardware.

https://sanny32.github.io/OpenModSim/

 

I'd love to download it but too many options.

My pc runs Windows 11, Version 25H2, Windows 11, Version 25H2 10.0.26200 x64-based

So which download do I choose? Qt5 or Qt6 or the x86?

 

My pc runs Windows 11, Version 25H2, Windows 11, Version 25H2 10.0.26200 x64-based

Prefer use Qt6 package for Windows 10 and above.

 

It works for me ! ! ! 5 stars * * * * *

I normally only use the data display, but I really like the traffic display with easy-to-read separate lines for Tx and Rx. Modscan's Master app just jams all the traffic in successive lines/rows and it's hard to read.

The flowmeter crowd that has totalizers using 64 bit registers should like this app.

I'll recommend it.

 

2.0.0 beta 1

This is a major beta version release with significant new features and platform support.

macOS Support

Native macOS build with DMG package, proper app icon, and .omsim file association. Available for Apple Silicon (arm64).

New Visual Theme Engine

Complete UI theming overhaul with light/dark mode support (macOS only).

Register Map View

New FormDataMapView with major improvements:

• Byte Order column
• Per-register descriptions and timestamps
• Row insert / move / delete
• Print support
• Auto-generate map from incoming master requests (#110)

Application Logging

Centralized log output panel (Log) with:

• Copy / export log
• Auto-show on warning or error
• Script start/stop events logged

JS Scripting: server.onRequest()

New JS API to intercept Modbus requests and return custom responses from scripts. See demos/ for examples.

UI & UX

• Welcome dialog on first launch
• Connected clients count in status bar
• Address Base and Hex View controls moved to main toolbar
• Redesigned force registers dialogs
• "Delete All", "Run All Scripts", "Stop All Scripts" in project tree context menu

Project Format

Project files renamed to .omsim. Settings format updated for version 2 (INI).

Platform Packages

• Windows: NSIS installer (Qt5 / Qt6)
• Linux: DEB (Ubuntu/Astra), RPM (Fedora/RHEL), Arch Linux
• macOS: DMG (Apple Silicon)