I spent three years using Modbus Poll for commissioning industrial PLCs. It worked fine. Then last year, our team needed UDP support for a building automation project, and Modbus Poll didn't have it. That's when I found ModbusSimulator.
After six months of using both tools across different projects, here's my honest comparison. I'm not going to pretend one is perfect and the other is garbage. Both are solid tools. But they serve slightly different needs, and the price difference is significant.
| Feature | Modbus Poll | ModbusSimulator |
|---|---|---|
| Price (Single User) | $129 | $99 (Master + Slave) |
| Free Trial | 30 days (limited) | 30 days (full features) |
| Modbus TCP | Yes | Yes |
| Modbus RTU | Yes | Yes |
| Modbus ASCII | Yes | Yes |
| Modbus UDP | No | Yes |
| Master Mode | Yes | Yes |
| Slave Mode | Separate app ($129) | Included |
| Multiple Connections | Up to 10 | Unlimited |
| Data Logging | CSV export | CSV export |
| Scripting | OLE/Automation | Not yet |
| Request Log | Yes | Yes (with scrollback) |
| Register Types | All 4 | All 4 |
| OS Support | Windows only | Windows only |
| Updates | 1 year included | Lifetime |
This is where it gets interesting. Modbus Poll charges $129 for the master application. But here's the thing most people don't realize until checkout: the slave simulator is a separate product called Modbus Slave, also $129. So if you need both master and slave (and most engineers do for testing), you're looking at $258.
ModbusSimulator bundles Master and Slave in one application for $99. That's it. One license, both modes, $99 one-time payment. For our team of three engineers, switching saved us about $477.
Both tools handle the three standard Modbus protocols well:
The key differentiator: ModbusSimulator supports Modbus UDP. Building automation systems, IoT gateways, and some SCADA setups use UDP for lower-latency communication. When our BACnet-to-Modbus gateway project needed UDP testing, Modbus Poll simply couldn't do it.
In master mode, both tools let you poll slave devices, read/write registers, and monitor responses. The workflow is similar: set up connection, configure read/write requests, start polling.
Modbus Poll has an edge in its OLE automation interface. If you script automated tests using VBScript, Modbus Poll can be controlled programmatically. ModbusSimulator doesn't have this yet, though its request log with scrollback is more useful for debugging individual transactions.
For manual testing and commissioning — which is 90% of what most engineers do — both tools are equally capable.
This is where ModbusSimulator really wins. With Modbus Poll, you need to buy Modbus Slave separately ($129). ModbusSimulator integrates both modes into one app.
The slave simulator lets you:
I've used it to simulate temperature sensors, flow meters, and VFD controllers when the actual hardware wasn't available yet.
Choose Modbus Poll if: Your workflow depends on automated testing scripts via OLE. Large enterprises with existing VBScript test suites should stick with it.
Choose ModbusSimulator if: You need both master and slave, want UDP support, prefer a modern UI, or want to save $159 per seat. This covers most engineers.
Starting fresh today, ModbusSimulator wins. You get master + slave for $99 vs $258, UDP support, and a modern UI. The only reason to choose Modbus Poll is OLE scripting automation.
Full features, no limitations during trial. Master + Slave included.
Download Free TrialIt has a free 30-day trial with full features. After that, it's $99 one-time. No free permanent version, but the trial is unrestricted.
Yes. It supports Modbus RTU over any serial port, including USB-to-RS485 adapters.
Currently Windows only, same as Modbus Poll.
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More guides: All blog posts · Modbus Register Types Guide