Has anyone seen a serial protocol sniffer for MODBUS


Thread Starter

Pierre Hinse CET

I'm looking for a serial protocol analyser that would sit in a laptop, and understands MODBUS.

Anyone out there have an idea?

Have a good weekend!


Sage, Pete (IndSys, GEFanuc, Albany)

I think a company called Frontier located in Charlottesville VA has the product you want. It comes with a couple different protocol decoders and I believe Modbus was one of them.

Just search for them on the web.
Good day,

As a functional tester for Allen Bradley, I am require to use Comlab. Of course, an understanding of the link layer is required.


I have played with a demo of a product developed by Calta Computer Systems. It is ideal for this problem. Try www.calta.com
If you want to monitor both sides of the communication it is easy to make a simple y cable. If you want the details of this let me know.

Craig Smith
The one I've used is by Prosoft Technology (www.psft.com) is called Data Analyzer Plus. It's cheap and easy to use but the inherent problem is that you need two serial ports if you want to see both sides of a Modbus conversation. I've used it with RTUs in wastewater applications and it's very clear and reliable. I couldn't find a part number on their website for it anymore,
so I assume that they're providing it as a utility to their hardware customers. A demo version is available from their FTP site.

Judging from the conversations on the A-list about Modbus character break specifications, you'll hear a lot of informed suggestions on this topic. Does anyone know of a protocol sniffer for

Ken Roach
A-B Seattle
Actually it is called "Frontline Test Equipment" and it is in Charlottesville VA (www.fte.com). They sent ISA some demo packages for use in the Industrial Networking course labs and I was impressed. It offered some excellent tools that
I typically only see in HP, Fireberd or Navtel $$$$ telco test units.

They have since called me and started asking alot of questions about both Modbus and DF1 and stated that they intend to develop decodes for both. Trouble is that I don't think they really believe there is a market, since DF1 doesn't exactly have the market awareness of say, PPP. So if everyone calls or emails Steve Liberman at Frontline Test Equipment and expresses interest in these decodes,
maybe they will actually do it. His email address is [email protected] and his telephone # is 804-984-4500. I would love to see a decent industrial analyzer finally hit the market.

Eric Byres, P.Eng.
ISA Instructor - TS05 Industrial Data Communications

[email protected]