Modbus protocol software.
Monitor, split and emulate Modbus data.

Modbus software

What is Modbus? Simply put, it is a method used to transmit serial information between electronic devices. Modbus is an open protocol that is free to use for commercial applications. It was developed by Modicon to control their programmable logic controllers (PLCs). The protocol is based on master-slave architecture.

In Modbus communication, the master broadcasts requests to the slave devices which return a response. Slave devices each have a distinct identifying address. The master can send messages and requests to individual slaves or to all of them simultaneously. When a response is required, the message is usually sent to a specific slave device. The slave address is the first byte in a request so the slaves know whether to listen or ignore the message.

Many industries use the Modbus protocol to establish serial communication between devices. It supports the TCP/IP and RS232/RS433/RS485 protocols. Also supported but less often seen is Modbus over UDP.


Table of contents:

  1. Modbus monitoring software
  2. Why split Modbus data?
  3. Share Modbus over Ethernet
  4. Third-party utilities for Modbus protocol

Modbus monitoring software


The serial implementations of Modbus are the ones most used in industry. There are two different variations of serial Modbus:

Modbus ASCII - uses ASCII characters for more human-readable communication. Checksums are derived using a longitudinal redundancy check (LRC). Messages begin with a colon (“:") and end with a newline character (CR/LF).

Modbus RTU is the variation most often employed. It presents data in a compact, binary format. A message is comprised of consecutive bytes with no spaces between them. Error checking is performed by appending a cyclic redundancy check (CRC) checksum to commands. Modbus RTU software identifies the end of a message by a 3.5 character space that acts as a delimiter.

If you are a software developer working with either Modbus ASCII or RTU, you could greatly benefit by using professional-grade Modbus software that can help you monitor and analyze data sent with the protocol.

Modbus monitoring software

Serial Port Monitor by Eltima Software analyzes and monitors both Modbus RTU and ASCII messages. It features a user-friendly interface and flexible filtering options that let you perform detailed analysis on Modbus communication.
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Serial Port Monitor

Log and analyze serial port activity
4.8 Rank based on 41+ users, Reviews(75)
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Serial Port Monitor

Modbus Protocol Analyzer is a Modbus utility that can be instrumental when troubleshooting issues with driver or application development. It can also be used for testing and optimization efforts in a Modbus network.

This professional Modbus monitoring software enables you to:

  • View monitored data in terminal, line, table or dump view for easier analysis. Filters can be used to limit the data and views can be employed singly or all at once for monitoring flexibility.
  • Multiple serial ports can be observed simultaneously in a single monitoring session. Data is captured on a first-in-first-out basis, making it easier to pinpoint serial communication issues.
  • Emulate serial data transfer to compare how a device or application responds. This feature is great for troubleshooting.
  • Serial ports that are in use by another program can be monitored immediately with no impact to the first application. Real-time data display facilitates the identification and monitoring of any problems.

Why split Modbus data?


A typical Modbus implementation is made up of a single controller or master and multiple sensors or slaves. They communicate with each other through a serial interface which is controlled by specialized serial software. Sometimes, several applications may need access to the port simultaneously. In order to accomplish this, you need to use 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. (12th Apr, 2018). 4.8 Rank based on 85+ users, Reviews(91)
Category: Communication Application
Virtual Serial Port Driver PRO is an advanced all-in-one utility that can be used to create and manage real and virtual RS485 port bundles.
Virtual Serial Port Driver PRO

Virtual COM Port Driver Pro by Eltima is an excellent solution for splitting Modbus data.

  • The application splits serial port traffic by duplicating data received by a COM port and forwarding it to an unlimited number of virtual or real serial interfaces.
  • Virtual COM Port Driver Pro allows duplication of data transmitted to a serial port so you can have multiple applications access it at the same time
  • Virtual COM Port Driver Pro enables the creation of an unlimited number of virtual RS232/RS422/RS485 ports as your system needs. This allows you to split Modbus traffic by creating virtual copies of a Modbus master’s COM port and using them to transmit data to the connected applications.

Share Modbus over Ethernet


The ability to share Modbus communication over Ethernet is another valuable feature of Serial to Ethernet Connector. It allows remote users to connect to a local Modbus device over an IP-based network.

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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. (26th Jan, 2017). 4.9 Rank based on 52+ users, Reviews(86)
Category: Communication Application
This communication application enables Modbus data to be shared with multiple network-attached users over TCP to UDP. There are no distance limitations enforced so you can access the data from any network-connected machine.
Serial to Ethernet Connector

  • The Modbus over IP application can be run as a background service. This fact enables you to close the application when you are not actively using it.
  • You can access up to 500 Modbus devices remotely at one time with this software tool.
  • You can back up the app’s configuration and easily move it to another computer to save yourself time and extra work.
  • There are Windows and Linux versions of Modbus to Ethernet Connector available. Please note that the Linux solution operates with a command-line interface.

Third-party utilities for Modbus protocol


QModMaster is a Qt-based app that simulates a master Modbus device. It’s a free tool that provides the user with a bus monitor with which to analyze traffic and a graphical user interface for ease of use.

SimplyModbusMaster - is an application that enables you to simulate a Modbus master using either the ASCII or RTU format. All information is displayed using a single window.

Simply Modbus Slave - Modbus slave software monitors master requests and can also be used in the RTU or ASCII Modbus formats. It uses one window for configuring and displaying settings. Another window is used for the data.

Modbus Poll is another application that is used to simulate a Modbus master device. It can be very helpful for developers working with Modbus slave devices. With this program, you can monitor multiple Modbus slaves or data areas at the same time. Testing is facilitated by creating and sending strings of test data in the app’s test center and reviewing the slave response in hex format.

Serial Port Monitor

Requirements: Windows (32-bit and 64-bit): XP/2003/2008/Vista/7/8/10, Windows Server 2012, Windows Server 2012/2016/2019 , 9.16MB size
Version 7.0.342 (13th Jan, 2018) Release notes
Category: Communication Application