Modbus software: test, monitoring and
master emulation

Olga Weis
Modbus software

Modbus is an openly published communication protocol built on a master-slave architecture. It is implemented in a wide range of industries for establishing communication among various electronic devices. Modbus protocol can be used for sending data over serial lines RS-485, RS-422, RS-232, and TCP/IP (Modbus TCP) protocols. Modbus over UDP is also possible although not widely used.

Contents


  1. Types of Modbus Software and their usage
  2. Modbus monitoring software
  3. The challenge of splitting Modbus data
  4. Share Modbus devices over TCP
  5. Master and Slave Modbus Simulators
  6. What is Modbus and how it works - basic principles

Types of Modbus Software and their usage


As mentioned before Modbus protocol is very widely implemented, especially the serial versions of it (RTU and ASCII ones). Modbus RTU is actually the most common usage of Modbus protocol. Are you developing software that communicates with electronic devices through Modbus RTU? In this case you will surely appreciate a high-quality Modbus RTU software for monitoring and analysis of data sent via this protocol. Same with Modbus ASCII variation.

Modbus monitoring software

SPM logo

Serial Port Monitor [Professional Edition]


Requirements: Windows (32-bit and 64-bit): XP/2003/2008/ Vista/7/8/10, Windows Server 2012. 9.16MB free space. Version 7.0.342. (16th Jan, 2018). 4.8 Rank based on 41+ users, Reviews(75)
Category: Serial Port Software
Serial Port Monitor developed by Eltima Software helps monitor and analyze messages sent through both variations of Modbus protocol. Its friendly interface shows comprehensive views of data and offers flexible filters for precise analysis.
Modbus monitoring tool

Modbus Protocol Analyzer offers a convenient way to track down the possible problems during development of an application or a driver, test and optimize serial devices, etc.

This professional Modbus test software allows you to:

  • Connect to a serial port that is already in use by a different program and start monitoring it right there. All data received by the port is shown in real time for immediate tracking of any possible issues.
  • Monitor several serial ports at the same time. You can analyze the activity of several Modbus ports in one session synchronously. Data flowing in both directions is conveniently recorded in a single log on a first-in first-out basis.
  • See the captured data in a table, terminal, line, and dump views at the same time. You can use various filters for precise monitoring.
  • Emulate the data transfer to a serial device to see exactly how it will react to specific commands.

The challenge of splitting Modbus data


As you already know, a typical Modbus communication is established between multiple sensors and a single controller (or a server) that receives the incoming data via a serial communication interface. This COM port is usually controlled by a specialized serial app. In many cases, however, it may be required to open the receiving port with several applications at a time. As a rule, this does not seem possible unless you use a dedicated Modbus splitter software.

Modbus splitter software

VSPD PRO logo

Virtual Serial Port Driver PRO


Requirements: Windows (32-bit and 64-bit): XP(only Standard)/2003(only Standard)/2008/ Vista/7/8/10, Windows Server 2012, Windows Server 2016. 6.54MB free space. Version 9.0.270. (13th Apr, 2018). 4.8 Rank based on 85+ users, Reviews(91)
Category: Serial Port Software
Virtual Serial Port Driver PRO — an advanced all-in-one utility to create and manage real and virtual RS485 port bundles.
Virtual Serial Port Driver PRO

Virtual COM Port Driver Pro by Eltima is probably the most optimal solution for this task. The program works as a serial port splitter able to duplicate data coming into one COM port to an unlimited number of real and virtual serial interfaces. Virtual COM Port Driver Pro will help you create as many virtual RS485 (RS232, RS422) ports as you need in your system. So if you want your Modbus traffic to be received by several apps simultaneously, you can simply create virtual copies of the master’s receiving COM port and connect the required apps to them. Virtual COM Port Driver Pro will duplicate the traffic to all of the virtual copies of the real COM port and this way several apps will be able to receive the same data at a time.

Share Modbus devices over TCP


Another special option that really deserves your attention is sharing Modbus over Ethernet. You can make a local Modbus device accessible to multiple remote users with the help of a handy network solution - Serial to Ethernet Connector.

Sec logo

Serial to Ethernet Connector


Requirements: Requirements for Windows (32-bit and 64-bit): XP/2003/2008/ Vista/7/8/10, Windows Server 2012. 4.66MB free space. Version 7.1.876. (29th Jan, 2017). 4.9 Rank based on 52+ users, Reviews(86)
Category: Serial Port Software
The software will let you both share Modbus over TCP (or UDP) among several users of your network and connect to remote Modbus equipment even when it is located miles away from your PC.
Serial to Ethernet Connector

This advanced utility makes it possible for you to work with up to 500 remote Modbus devices at a time. A really nice thing about the Modbus over IP software is that it can run in the background as a service, which means you don’t need to always keep it open. What’s more, the program is able to backup a configuration and move it to another machine this way saving you time and effort.

For now, Modbus to Ethernet Connector is available for Windows and Linux platforms. And the version for Linux is a command-line solution.

Master and Slave Modbus Simulators


  • QModMaster is a Qt-based app simulating a Modbus master. This software is free of charge and offers a comprehensive graphical interface and a bus monitor for traffic analysis.
  • SimplyModbusMaster -can simulate a Modbus RTU or a Modbus ASCII Master. It displays all information in a single window.
  • Modbus RTU Slave and Modbus ASCII Slave Software - works as a Modbus RTU Slave or a Modbus ASCII Slave and monitors master requests. One window is used for entering and displaying the settings, and the second window - for the data.
  • Modbus Poll features a multiple document interface and simulates a Modbus master. A good helper app for those who are developing the Modbus slave devices. This Modbus software can monitor several Modbus slaves and/or data areas simultaneously. Developers have the possibility to create and send their own test strings in the "test center" and get the result from the slave in hexadecimal format.

What is Modbus and how it works - basic principles


Modbus protocol is a messaging structure of a master-slave communication between intelligent electronic devices. As a rule signals are transferred from devices back to a main controller or a resource gathering the data. A master device can direct a request individually to a slave device or broadcast it to all slaves. When individual signal is received, the slave will respond, whereas when the signal is broadcast, the response is usually not anticipated. The first byte the master sends is the slave address. This way each slave device knows whether to ignore the message or to listen to it after this first byte.

There are two variations of Modbus protocol used in serial communication:

  • Modbus ASCII - uses ASCII characters for protocol communication. The longitudinal redundancy check checksum is used and the messages are framed by a leading colon (":") and a trailing newline (CR/LF).
  • Modbus RTU - this protocol shows data in a compact binary view. RTU checks info for errors by following the commands with a cyclic redundancy check checksum. Bytes are sent consecutively without spaces between them with a 3.5 character space between messages for a delimiter. This is how the software knows that a new message has started. RTU messages are framed by idle periods.

Serial Port Monitor

Requirements: Windows XP/2003/2008/Vista/7/8/10/Server 2012 , 9.16MB size
Version 7.0.342 (16th Jan, 2018) Release notes
Category: Serial Port Software