# Open ModSim

[](https://github.com/sanny32/OpenModSim/releases)

[](https://github.com/sanny32/OpenModSim/releases/latest)

[](LICENSE.md)

Open ModSim is a free implimentation of modbus slave (server) utility for modbus-tcp and modbus-rtu protocols.

<img width="1292" height="759" alt="image" src=".github/assets/omodsim-dataview.png" />

<img width="1292" height="759" alt="image" src=".github/assets/omodsim-mapview.png" />

# Features

The following Modbus functions are available:

- Discrete Coils/Flags

```

0x01 - Read Coils

0x02 - Read Discrete Inputs

0x05 - Write Single Coil

0x0F - Write Multiple Coils

```

- Registers

```

0x03 - Read Holding Registers

0x04 - Read Input Registers

0x06 - Write Single Register

0x10 - Write Multiple Registers

0x16 - Mask Write Register

```

The following simulations are available:

- Discrete Coils/Flags

```

Random - simulate flag randomly

Toggle - simulate flag on/off periodicaly

```

- Registers

```

Random - simulate register randomly

Increment - simulate register from Low Limit to High Limit with a given Step

Decrement - simulate register from High Limit to Low Limit with a given Step

```

# Modbus Logging

<img width="1292" height="759" alt="image" src=".github/assets/omodsim-trafficview.png" />

# Extended Featues

- Modbus Message Parser

<img width="674" height="463" alt="image" src=".github/assets/omodsim-msg-parser.png" />

- Modbus Definitions

<img width="416" height="346" alt="image" src=".github/assets/omodsim-modbus-defs.png" />

- Error Simualtions

<img width="416" height="346" alt="image" src=".github/assets/omodsim-modbus-errsim.png" />

# Scripting

From version 1.2.0 Open ModSim supports scripting. Qt runtime implements the [ECMAScript Language Specification](http://www.ecma-international.org/publications/standards/Ecma-262.htm) standard, so Javascript is used to write code.

<img width="1288" height="749" alt="image" src=".github/assets/omodsim-script.png" />

Scripts can be launched in two modes: Once or Periodically. If you run script in Once mode the script will stop after it finishes executing. In Periodically mode, the script will start after a certain period of time until the user stops it or the method is called

```javascript

Script.stop();

```

> [!NOTE]

> In Periodically mode the whole script is re-executed on every period, so top-level variables are reset on each run. Only the code passed to `Script.onInit()` runs once, and only values kept in `Storage` persist between runs. Use `Storage.setItem()` / `Storage.getItem()` to keep state (counters, flags, etc.) across periods.

Here is an example of using the script in the Periodically mode

```javascript

/**************************************************************************/

/*

/* Example script that store value after 3 seconds

/*

***************************************************************************/

/* Set the server address base starts from one (1-based) */

Server.addressBase = AddressBase.Base1;

let deviceId = 1;

let address1 = 1;

let address10 = 10;

function reset()

{

/* Write to a Holding register at address1 zero value */

Server.writeHolding(address1, 0, deviceId);

}

/* init function */

function init()

{

reset();

/* Print server error if occured and stop script execution */

Server.onError(deviceId, (error)=> {

console.error(error);

Script.stop();

});

/* Runs when Hodling register value at address1 was changed */

Server.onChange(deviceId, Register.Holding, address1, (value)=>

{

if(value === 1)

{

/* Runs after 3 seconds and increase Holding register value at address10

* Then reset register value at address1 and stop script execution

*/

Script.setTimeout(function()

{

Server.writeHolding(address10, Server.readHolding(address10, deviceId) + 1, deviceId);

reset();

Script.stop();

}, 3000);

}

});

}

/* Runs once when script started */

Script.onInit(init);

```

# About supported operating systems

The following minimum operating system versions are supported for OpenModSim:

- <img src="docs/icons/logo_windows7.svg" width="16" height="16" /> **Microsoft Windows 7**

- <img src="docs/icons/logo_apple.svg" width="16" height="16" /> **macOS 15 (Sequoia)**

- <img src="docs/icons/logo_debian.svg" width="16" height="16" /> **Debian Linux 12**

- <img src="docs/icons/logo_ubuntu.svg" width="16" height="16" /> **Ubuntu Linux 22.04**

- <img src="docs/icons/logo_mint.png" width="16" height="16" /> **Mint Linux 22**

- <img src="docs/icons/logo_zorin.png" width="16" height="16" /> **Zorin OS 18**

- <img src="docs/icons/logo_fedora.svg" width="16" height="16" /> **Fedora Linux 43**

- <img src="docs/icons/logo_rocky.png" width="16" height="16" /> **Rocky Linux 9.7**

- <img src="docs/icons/logo_opensuse.svg" width="16" height="16" /> **OpenSuse Linux 15.6**

- <img src="docs/icons/logo_alt.png" width="16" height="16" /> **Alt Linux 11**

- <img src="docs/icons/logo_astra.png" width="18" height="18" /> **Astra Linux 1.7**

- <img src="docs/icons/logo_redos.png" width="16" height="16" /> **RedOS 8**

- <img src="docs/icons/logo_arch.svg" width="16" height="16" /> **Arch** (manual building only)

# Building

Building is available via cmake (with installed Qt version 5.15 and above) or Qt Creator. Supports both OS Microsoft Windows and Linux.

> [!NOTE]

> Building from source requires CMake version @CMAKE_MIN_REQ_VERSION@ or newer.

## Microsoft Windows Building

The minimum supported version of Microsoft Windows for building OpenModSim from sources is Windows 10.

1. Install latest [git](https://git-scm.com/downloads/win) version

2. Run Windows PowerShell terminal as an Administrator

3. Clone OpenModSim sources from github repository

```powershell

git clone https://github.com/sanny32/OpenModSim.git

```

4. Go to OpenModSim folder

```powershell

cd OpenModSim

```

5. Allow script execution in PowerShell terminal

```powershell

Set-ExecutionPolicy -Scope Process -ExecutionPolicy Bypass

```

6. Run the build script

```powershell

.\build.ps1

```

If you need to specify Qt framework major version (5 or 6), you can do it in the parameters

- `.\build.ps1 -qt5` or `.\build.ps1 -qt6`

To enable the experimental [Qlementine](https://github.com/oclero/qlementine) application style (requires Qt6 >= 6.8):

- `.\build.ps1 -qlementine`

The build script supports building the application only for 64-bit architecture.

## Linux Building

1. Install [git](https://git-scm.com/downloads/linux) for your Linux distribution

2. Run the following commands from the console:

```bash

git clone https://github.com/sanny32/OpenModSim.git

```

```bash

cd OpenModSim

```

```bash

./build.sh

```

If you need to specify Qt framework major version (5 or 6), you can do it in the parameters

- `./build.sh -qt5` or `./build.sh -qt6`

To enable the experimental [Qlementine](https://github.com/oclero/qlementine) application style (requires Qt6 >= 6.8):

- `./build.sh -qlementine`

## macOS Building

The minimum supported version of macOS for building OpenModSim from sources is macOS 15 (Sequoia).

1. Install [Homebrew](https://brew.sh) if not already installed

2. Install required dependencies:

```bash

brew install qt@6 cmake ninja

```

3. Clone OpenModSim sources from github repository:

```bash

git clone https://github.com/sanny32/OpenModSim.git

```

4. Go to OpenModSim folder:

```bash

cd OpenModSim

```

5. Run the build script:

```bash

./build-macos.sh

```

> [!NOTE]

> On macOS, OpenModSim uses [**Qlementine**](https://github.com/oclero/qlementine) style and [**Qlementine Icons**](https://github.com/oclero/qlementine-icons) by default when building with **Qt6 >= 6.8**.

> These dependencies are fetched automatically during CMake configure and improve icon/theme consistency on macOS.

> If you build with Qt5 or Qt6 < 6.8, OpenModSim falls back to the standard built-in style.

The build script generates a macOS application bundle (`omodsim.app`). To run the application:

```bash

open build-omodsim-Qt_*/omodsim.app

```

# Install from [binary distributions](https://github.com/sanny32/OpenModSim/releases/latest)

Below are the methods for installing the OpenModSim for different OS

## <img src="docs/icons/logo_windows.svg" width="16" height="16"> Microsoft Windows

Run the installer:

- For 32-bit Windows: `qt5-omodsim@VERSION_MAJOR@-@PROJECT_VERSION@_x86.exe`

- For 64-bit Windows: `qt5-omodsim@VERSION_MAJOR@-@PROJECT_VERSION@_x64.exe` or `qt6-omodsim@VERSION_MAJOR@-@PROJECT_VERSION@_x64.exe`

## <img src="docs/icons/logo_apple.svg" width="16" height="16"> macOS

### Install

Open the DMG package:

```bash

open qt6-omodsim@VERSION_MAJOR@-@PROJECT_VERSION@_arm64.dmg

```

Then drag `Open ModSim @VERSION_MAJOR@.app` to the `Applications` folder.

Before the first launch, allow the application to run in `System Settings` > `Privacy & Security`, or remove the quarantine attribute from the command line:

```bash

xattr -dr com.apple.quarantine "/Applications/Open ModSim @VERSION_MAJOR@.app"

```

Run the application:

```bash

open "/Applications/Open ModSim @VERSION_MAJOR@.app"

```

### Remove

To remove the application, move it to Trash or run:

```bash

rm -rf "/Applications/Open ModSim @VERSION_MAJOR@.app"

```

## <img src="docs/icons/logo_debian.svg" width="20" height="20"> Debian • <img src="docs/icons/logo_ubuntu.svg" width="20" height="20"> Ubuntu • <img width="20" height="20" src="docs/icons/logo_mint.png" /> Mint • <img src="docs/icons/logo_zorin.png" width="20" height="20"> Zorin • <img width="22" height="22" src="docs/icons/logo_astra.png" /> Astra Linux

### Install

Install the DEB package from the command line:

```bash

sudo apt install ./qt6-omodsim@VERSION_MAJOR@_@PROJECT_VERSION@-1_amd64.deb

```

or if you want to use Qt5 libraries:

```bash

sudo apt install ./qt5-omodsim@VERSION_MAJOR@_@PROJECT_VERSION@-1_amd64.deb

```

### Remove

To remove the DEB package run:

```bash

sudo apt remove qt6-omodsim@VERSION_MAJOR@

```

or for Qt5 package:

```bash

sudo apt remove qt5-omodsim@VERSION_MAJOR@

```

## <img src="docs/icons/logo_redhat.svg" width="24" height="24"> RedHat • <img src="docs/icons/logo_fedora.svg" width="20" height="20"> Fedora • <img src="docs/icons/logo_rocky.png" width="20" height="20"> Rocky • <img width="20" height="20" src="docs/icons/logo_redos.png" /> RedOS Linux

### Install

Install the RPM package from the command line:

```bash

sudo dnf install ./qt6-omodsim@VERSION_MAJOR@-@PROJECT_VERSION@-1.x86_64.rpm

```

### Remove

To remove the RPM package run:

```bash

sudo dnf remove qt6-omodsim@VERSION_MAJOR@

```

## <img src="docs/icons/logo_alt.png" width="24" height="24"> Alt Linux

### Install

Install the RPM package from the command line as root user:

```bash

apt-get install ./qt6-omodsim@VERSION_MAJOR@-@PROJECT_VERSION@-1.x86_64.rpm

```

### Remove

To remove the RPM package run as root user:

```bash

apt-get remove qt6-omodsim@VERSION_MAJOR@

```

## <img width="20" height="20" src="docs/icons/logo_suse.png" /> SUSE • <img src="docs/icons/logo_opensuse.svg" width="24" height="24" /> OpenSUSE Linux

### Install

Import qt6-omodsim@VERSION_MAJOR@.rpm.pubkey to rpm repository:

```bash

sudo rpm --import qt6-omodsim@VERSION_MAJOR@.rpm.pubkey

```

Install the RPM package using Zypper:

```bash

sudo zypper install ./qt6-omodsim@VERSION_MAJOR@-@PROJECT_VERSION@-1.x86_64.rpm

```

### Remove

To remove the RPM package run:

```bash

sudo zypper remove qt6-omodsim@VERSION_MAJOR@

```

# Code Signing Sponsor

Windows binaries for this project are signed thanks to **SignPath Foundation**.

* 🔐 **Free code signing service:** [SignPath.io](https://signpath.io)

* 📜 **Certificate provider:** [SignPath Foundation](https://signpath.org)

# MIT License

Copyright 2023-2026 Alexandr Ananev [mail@ananev.org]

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.