If you work in industrial automation, SCADA commissioning, PLC programming, or substation telemetry, you have almost certainly encountered Modbus Poll. Developed by Witte Software, Modbus Poll is one of the oldest and most widely used Modbus master simulation tools in the industry.
However, when setting up new test benches, outfitting field engineering teams, or renewing enterprise compliance licenses, navigating Modbus Poll's licensing structure can quickly become confusing and unexpectedly expensive. From separate licenses for Master vs. Slave modes to strict node-locking and 10-minute timeout limits, understanding your options before purchasing is essential.
This comprehensive guide breaks down all Modbus Poll license types, official 2026 pricing, trial restrictions, and how modern alternatives like ModbusSimulator deliver a unified Master + Slave experience at a fraction of the cost.
Key Takeaway for Buyers:
Modbus Poll licenses cost $129 for Master mode alone. To simulate Modbus devices as a Slave/Server, you must buy a second, separate $129 license for Modbus Slave ($258 total). Modern alternatives like ModbusSimulator bundle Master and Slave into a single $59 perpetual license.
Modbus Poll License Types & Pricing Structure (2026)
Modbus Poll is distributed under a commercial proprietary licensing model. Below is the breakdown of available license tiers:
| License Tier | Modbus Poll (Master) | Modbus Slave (Server) | Combined Cost |
|---|---|---|---|
| Single-User License | $129 USD | $129 USD | $258 USD |
| 5-User Multi-Pack | $549 USD | $549 USD | $1,098 USD |
| 10-User Multi-Pack | $899 USD | $899 USD | $1,798 USD |
| Site License (Single Facility) | $1,299 USD | $1,299 USD | $2,598 USD |
The Two-Application Dilemma: Master vs Slave
The most common complaint among control systems engineers is that Modbus Poll only acts as a Master (Client). If your testing scenario requires simulating a field device—such as a solar inverter, power meter, temperature transmitter, or remote RTU—to test your SCADA or PLC logic, Modbus Poll cannot perform this role.
You must download and purchase Modbus Slave as an entirely separate product. This means keeping two distinct application windows open, managing two separate license keys, and paying double the price.
Trial Restrictions: What Happens Without a Valid License Key?
Modbus Poll provides a 30-day evaluation trial. While functional for initial testing, the unactivated software imposes strict operational constraints:
- 10-Minute Disconnect Timeout: After the trial period, the software automatically cuts active TCP and serial polling connections every 10 minutes. This makes overnight endurance testing or automated test harness execution impossible.
- Modal Dialogue Interruptions: Periodic popups require manual user clicks to dismiss, pausing register acquisition loops.
- Limited Logging & Scripting: Advanced Excel VBA integration, automated OLE automation scripts, and continuous CSV data logging are restricted.
Feature & Pricing Comparison: Modbus Poll vs ModbusSimulator
To help engineers and project managers evaluate their options, here is a direct side-by-side technical comparison:
| Capability | Modbus Poll + Slave | ModbusSimulator.com |
|---|---|---|
| Total License Cost | $258 USD (Separate purchases) | $59 USD (Single license) |
| Master & Slave in One App | ❌ No (Two separate programs) | ✅ Yes (Instant 1-click toggle) |
| Protocols Supported | Modbus TCP, RTU, ASCII | All 8 Variants (TCP, RTU, ASCII, RTU/TCP, ASCII/TCP, UDP, RTU/UDP) |
| Dynamic Waveform Simulation | Basic increment/random | Sine, Cosine, Triangle, Ramp, Noise, Custom Math Formulas |
| High-DPI / Windows 11 UI | Legacy Win32 interface | Modern, Dark/Light mode, 4K high-DPI scaling |
| License Activation & Portability | Node-locked per PC | Flexible activation across development & laptop devices |
Why Engineers Choose ModbusSimulator Over Modbus Poll
- Save Nearly $200 per Engineer: By offering complete Master (Client) testing and Slave (Server) device simulation in a single package for $59, engineering departments cut their software testing budgets by over 75%.
- Test All 8 Protocol Variations: In modern industrial facilities, gateways frequently encapsulate Modbus RTU over TCP or ASCII over UDP. ModbusSimulator supports all 8 encapsulation variants out of the box.
- Realistic Field Device Simulation: Generate live dynamic process values—such as fluctuating kilowatt-hour power demands, fluctuating tank temperatures, or sine-wave vibration signals—to verify SCADA alarm setpoints and historian trending.
Frequently Asked Questions
How much does a Modbus Poll license cost in 2026?
A standard single-user commercial license for Modbus Poll costs $129 USD. However, this license only enables Modbus Master (Client) functionality. If you also require Modbus Slave (Server) simulation, you must purchase a separate license for Modbus Slave for an additional $129 USD, bringing the total combined cost to $258 USD per workstation.
What is the difference between Single-User, Multi-User, and Site Licenses for Modbus Poll?
A Single-User license ($129) permits one designated engineer to run the software on a single computer. Multi-user pack licenses offer slight per-seat volume discounts for 5 to 20 engineers. A Site License ($1,299+) grants unlimited installations for employees located within a single physical office or plant facility.
Does a Modbus Poll license include free lifetime updates?
Modbus Poll licenses typically include minor version bug fixes and updates within the same major version release. Major version upgrades or cross-platform migrations often require purchasing upgrade licenses.
What are the limitations of running Modbus Poll without a license key?
When running in unlicensed evaluation mode after the initial 30-day trial period, Modbus Poll automatically terminates communication sessions every 10 minutes, displaying modal registration dialogue boxes that block automated or continuous SCADA integration tests.
Is there an all-in-one alternative that includes both Master and Slave modes?
Yes. ModbusSimulator.com provides a modern, unified application that includes both full Modbus Master and full Modbus Slave simulation in a single license for $59 USD (perpetual). This eliminates the need to buy and switch between two separate applications while saving engineers nearly $200.
Can I transfer my Modbus license to a new PC or field laptop?
Yes. ModbusSimulator licenses use simple, flexible license keys that can be deactivated and transferred between development workstations, testing VMs, and field commissioning laptops without restrictive hardware-dongle locks.
Experience the Modern Modbus Alternative
Download ModbusSimulator today with a full 30-day free trial — no credit card, no 10-minute timeouts, and full Master + Slave support.