5 Best Modbus Simulator Tools in 2026

Modbus simulator tools are essential for automation engineers, system integrators, and developers who need to test, debug, and validate Modbus communication. Whether you're testing a new PLC, developing a SCADA system, or troubleshooting a field device, having the right tool saves significant time.

This guide compares the five best Modbus simulator and poll tools available in 2026, covering features, protocol support, pricing, and best use cases.

What to Look For in a Modbus Simulator

Before choosing a tool, consider these key criteria:

• Protocol support — Does it support TCP, RTU, ASCII, and hybrid variants?
• Master and Slave modes — Can it both poll devices and simulate them?
• Function codes — How many function codes are supported? Basic tools only do FC01–FC06.
• Display formats — Can it show data as float, signed, hex, BCD, and handle byte-order variations?
• Data logging — Can it log to CSV/XLSX for analysis?
• Diagnostics — Address scanner, raw frame sending, communication logger?
• Price — One-time purchase vs. subscription? Master and Slave included or separate?

1. Modbus Simulator (ModbusSimulator)

Best for: Engineers who need Master + Slave in one tool with comprehensive protocol support

Modbus Simulator is a professional desktop application that bundles both Master and Slave modes in a single license. It supports 8 protocol variants (TCP, UDP, RTU, ASCII, and all four cross-framing combinations), 14 function codes, and 21+ display formats.

Key Features

• Master and Slave modes included in one license
• 8 protocol variants: TCP, UDP, RTU, ASCII, RTU-over-TCP, ASCII-over-TCP, RTU-over-UDP, ASCII-over-UDP
• 14 function codes including FC08 Diagnostics, FC22 Mask Write, FC23 Read/Write, FC43 Device Info
• 21+ display formats with 4 byte-order options
• Address scanner for device discovery on serial buses
• Test center for sending raw Modbus frames
• Data logging to CSV and XLSX with real-time recording
• Live data charts with up to 8 simultaneous traces
• REST API for Excel/VBA integration
• Scaling, offset, and conditional color rules
• ENRON/DANIEL extended addressing support

Pricing

$99 one-time purchase for a perpetual license. Volume pricing available at $79/license for 3 or more. Free lifetime updates and email support included.

Platform

Windows 10/11 (64-bit)

2. Modbus Poll (Witte Software)

Best for: Users who only need a Master (client) tool

Modbus Poll by Witte Software is a well-known Modbus master simulator. It can poll Modbus slave devices using TCP, RTU, and ASCII protocols. It supports multiple simultaneous poll windows and various data display formats.

Key Features

• Master mode only (Slave sold separately as "Modbus Slave")
• TCP, RTU, ASCII support
• Multiple poll windows
• OLE/ActiveX automation support
• Data logging to text files
• Print and export functionality

Pricing

$129 for Modbus Poll (Master only). Modbus Slave is an additional $129. Total for both: $258.

Platform

Windows

3. Simply Modbus

Best for: Quick, simple testing with a lightweight tool

Simply Modbus offers separate Master and Slave applications with a straightforward interface. It focuses on simplicity over advanced features, making it suitable for basic testing needs.

Key Features

• Separate Master and Slave applications
• TCP and RTU support
• Basic function codes (FC01–FC06, FC15, FC16)
• Simple tabular data display
• Lightweight and easy to learn

Pricing

$79 for Master, $79 for Slave. Both needed: $158.

Platform

Windows

4. QModMaster

Best for: Open-source/free option for basic testing

QModMaster is a free, open-source Modbus master application built with Qt. It provides basic master functionality for TCP and serial connections and is a good option for engineers on a budget who only need simple polling capabilities.

Key Features

• Free and open-source
• Master mode only
• TCP and serial RTU support
• Basic function codes (FC01–FC06, FC15, FC16)
• Bus monitor for viewing raw traffic
• Cross-platform (Windows, Linux)

Pricing

Free (open-source)

Platform

Windows, Linux

5. ModRSsim2

Best for: Free Modbus slave/server simulation

ModRSsim2 is a free Modbus slave simulator that can emulate multiple Modbus servers. It supports TCP, RTU, and ASCII and allows you to configure register values for testing your master applications.

Key Features

• Free to use
• Slave/server mode only
• TCP, RTU, ASCII support
• Simulate multiple slave IDs
• Edit register values interactively
• Script-based value simulation

Pricing

Free

Platform

Windows

Feature Comparison

Feature	ModbusSimulator	Modbus Poll	Simply Modbus	QModMaster	ModRSsim2
Master Mode	Yes	Yes	Yes	Yes	No
Slave Mode	Yes	No*	Yes*	No	Yes
Protocol Variants	8	3	2	2	3
Function Codes	14	8	8	8	8
Display Formats	21+	10+	5+	3	3
Data Logging	CSV, XLSX	Text	No	No	No
Address Scanner	Yes	No	No	No	No
Live Charts	Yes	No	No	No	No
REST API	Yes	OLE	No	No	No
Price (Both Modes)	$99	$258	$158	Free	Free

* Separate purchase required for slave mode

Which Tool Should You Choose?

The right tool depends on your needs and budget:

• Need both Master and Slave with full feature set? — Modbus Simulator offers the most features at the best price point ($99 for both modes).
• Only need a basic master for quick tests? — QModMaster is free and covers the basics.
• Need a free slave simulator? — ModRSsim2 is a solid choice for testing your master applications.
• Already using Witte Modbus Poll? — It's a mature product, though you'll pay extra for slave mode and get fewer features.

For a hands-on guide to using these tools, see our step-by-step testing guide. If you're new to the protocol, start with what is Modbus protocol.