| ModbuxPloxc | Modbus Poll / SlaveWitte Software | QModMasteropen source | ModbusToolsopen source | |
|---|---|---|---|---|
| Price | Free | $129 each, perpetual | Free | Free |
| Source available | Yes | No | Yes | Yes |
| Client (master) | Yes | Yes, Modbus Poll | Yes | Yes |
| Server (slave) simulation | Yes, included | Yes, Modbus Slave sold separately | No | Yes |
| Windows | Yes | Yes | Yes | Yes |
| macOS | Yes, Intel and Apple Silicon | No | Build from source | No |
| Linux | Build from source, .deb and AppImage | No | Build from source | Yes |
| Built with | Electron and React | Native Windows | Qt and libmodbus | C++ and Qt |
Modbus Poll is the tool most people in industrial automation learn Modbus on, and it has earned that position over more than twenty years. It is dependable, it is fast, and it does exactly what it says.
It is also Windows-only, and the master and slave sides are two separate purchases. A commissioning engineer who wants to poll a device and simulate one pays $258 and still cannot run either on a Mac. Modbux puts the client and the server in one free application, and adds a Split mode that runs both side by side in separate windows so you can test a PLC implementation against your own simulation before you are on site.
This is the gap that is hardest to fill. The commercial tools are Windows-only. The open-source Qt projects, QModMaster and ModbusTools, publish Windows binaries and expect macOS users to build from source, which means installing Qt and a toolchain before you can read a single register.
Modbux ships Intel and Apple Silicon builds as a normal .dmg, alongside the Windows installer. Serial ports are discovered automatically on both platforms, and RTU over TCP covers serial-to-Ethernet gateways such as a Moxa in transparent mode.
One caveat, stated plainly: Modbux is not yet signed with an Apple Developer certificate, so macOS Gatekeeper may report it as damaged on first launch. It takes one command in Terminal to clear, and the getting started guide walks through it.
Modbus tooling is visually stuck around 2005. That is not only a matter of taste: it shows up as grey grids that make you guess which data type is correct, and register values you have to reinterpret by hand.
Modbux is an Electron and React application with a dark interface built for long sessions, and its Advanced Mode shows every numeric interpretation of a register side by side, so you stop guessing. There are 12 data types, including 64-bit integers, doubles, UTF-8 strings, Unix timestamps and IEC 870-5 datetimes, assignable per register with scaling and linear interpolation.
Bitmaps get an expandable 16-bit panel with per-bit toggles, colour coding, invert logic and inline comments. Read configuration mode polls only the registers you have configured, grouping them automatically and showing errors inline. Unit ID and register range scanning find devices and data when the documentation is wrong.
You need Linux today. ModbusTools has proper Linux support. Modbux can be built for Linux from source, but there is no published Linux release yet.
You need Modbus ASCII, or Modbus over UDP. Modbux covers Modbus TCP, Modbus RTU and RTU over TCP. ModbusTools covers a wider set of protocol variants.
Your employer requires a commercial support contract. Witte Software sells one and has done for two decades. Modbux is supported through GitHub issues, by one maintainer.
You want the smallest possible footprint. An Electron application is larger than a native Qt one, roughly 80 MB on Windows against a few megabytes for QModMaster.
Yes. Modbux is a free, open-source Modbus client and server for Windows and macOS. Modbus Poll is Windows-only and costs $129 per licence, with the matching Modbus Slave server sold separately for another $129. Modbux includes both the client and the server in one application.
Modbux runs natively on macOS, on both Intel and Apple Silicon, as well as on Windows. Most established Modbus test tools are Windows-only, and the open-source Qt-based alternatives ship Windows binaries but leave macOS users to build from source.
Yes. Modbux includes a server mode that simulates Modbus devices over TCP or RTU, with up to 10 TCP servers of 256 unit IDs each and value generators for realistic test data. Split mode runs the client and server side by side so you can test a PLC implementation before going on site.
Modbux is an Electron and React desktop application. That is what allows a single modern interface to run identically on Windows and macOS, instead of the Qt and native Win32 interfaces most Modbus tooling still uses.