Compare Modbus test tools

Facts about other tools come from their own pages, read on 6 November 2026. Products change, so verify on the vendor site. Busscope is independent and not affiliated with any tool named here. Product names belong to their owners.

How to pick a Modbus test tool

Modbus tools fall into a few groups. Masters, also called clients, talk to devices and show what they answer. Slave simulators play the device. Loggers and viewers collect values over time. A few tools do more than one of these. The right choice depends on the job, the protocol variant, your operating system and your budget. The tables below set out what each project says about itself. Where a page does not state a fact, the table says so instead of guessing. Two questions help most: which protocol variant does your device speak, and do you need to poll it, simulate it or watch it over days? Answer those first, and the choice usually narrows to two or three tools that you can then try side by side.

Master and client tools

Slave and simulator tools

Logging and visualization

ModbusScope is an open-source project under GPL v3 for logging and visualizing data over Modbus. According to its project page it offers real-time visualization, zooming, markers, continuous logging, support for multiple devices, CSV export and calculations that combine several registers into one value. It is a graphing tool first, so it complements a master rather than replacing one. The names ModbusScope and Busscope sound alike, but the projects are unrelated.

Busscope Master has live charts and logging to CSV or Excel inside the same window as the poll windows, which suits quick checks. For long-term trend work with calculated values, a dedicated logger may serve you better.

What Busscope adds

• TLS in the master: Modbus/TCP Security with TLS 1.2 or newer, client certificate and CA file. See Modbus TCP Security (TLS).
• Request Runner and Register Probe: script a sequence of requests, and find readable and illegal address ranges on an undocumented device.
• Serial tools: RS-485 echo removal and RTS toggle. See the RS-485 echo and RTS guide.
• Both sides in one family: a master and a slave simulator with the same look and feel, each with its own license.
• Price: perpetual licenses from $39 per user while the launch price lasts.

What Busscope does not do

Busscope runs on Windows only. Busscope Master does not list UDP or RTU over TCP, and Busscope Slave answers over TCP and RTU only. It has no scripting API such as OLE Automation. It is also a young product with fewer years of field use than long-established tools. If any of that matters for your job, choose a tool that covers it.

Which tool for which job

• Check a PLC or meter on Windows: a master with poll windows and write dialogs. See the Modbus TCP tester and Modbus RTU tester pages.
• Test a SCADA screen with no hardware: a slave simulator with editable values. See Modbus slave simulator for Windows.
• Run on Linux or in a script: QModMaster or diagslave fit better than a Windows-only tool.
• Trend charts over days: a logger such as ModbusScope.
• Replace Modbus Poll on a budget: see the Modbus Poll alternative page.

Check the facts yourself

Run each candidate against the same device. Compare byte order, timeouts, error handling, how a write is confirmed and how the tool shows the raw frames. A free evaluation of Busscope Master and Busscope Slave is on the download page, and the documentation has reference pages on register addressing, exception codes and frame decoding that apply to any tool.

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