Modbus over Ethernet
Access Modbus data over IP

Modbus is a standard protocol for serial communication. Popular across industries, it is often used to connect various industrial electronic devices and instruments to a system that gathers data or a main controller. A common example would be a device that measures temperature and humidity level and sends collected data to the control center via a computer.


What is Modbus?

The serial communication protocol known as Modbus was developed and published in 1979 by Modicon® with the intent to deploy it in their programmable logic controllers (PLCs). The protocol is basically a technique of enabling data transmission between devices via a serial interface. The Modbus Master is the name for the device that requests data. Its data requests are handled by devices known as Modbus Slaves. There is a single Master in the standard Modbus network configuration, and up to 247 Slave devices uniquely identified by a Slave Address from 1 to 247. The Master has the ability to write to the Slave devices.


The official specifications of the Modbus protocol are defined here

Uses of Modbus

Manufacturers can incorporate Modus into their equipment royalty-free since it was developed as an open protocol. It is widely used when connecting industrial electronic devices and has evolved to become a common communications protocol used extensively in industry and manufacturing. The protocol is primarily used to enable the data transmission that is required between remote instruments and the central data server or controller. An example is a pressure monitoring device that updates the central computer through serial communication. Supervisory control and data acquisition (SCADA) systems often use the Modbus protocol to communicate between a remote terminal unit (RTU) and the supervisory computer. There are versions of the Modbus protocol available for (Modbus RTU and Modbus ASCII) and for Ethernet (Modbus TCP).

What is Modbus TCP/IP protocol?

Modbus TCP/IP is one kind of Modbus protocols designed for controlling and supervising equipment over TCP or IP. It is possible to use Modbus over Internet or Intranet if a device supports TCP/IP sockets and you know how to execute a TCP driver.
Else, there are alternative ways of doing it, we’ll talk about them below.

To start working with a COM port, download and install the app, it will display a list of devices available to you, find the one you need and connect to it. Serial to Ethernet Connector enables access to serial port in Hyper-V, VMWare, Citrix XenDesktop and other virtualization software.
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Sharing Modbus RTU/ ASCII over Ethernet

Software solution

This is special software - Serial to Ethernet Connector that allows you to work with Modbus to Ethernet. It enables you to provide shared access to a local Modbus device over network, so other network users can reach its content and functionality as if it were attached directly to their machines. In a similar way you too can access a remote Modbus over Ethernet regardless your physical proximity to the device. The number of devices you can work with over network can be up to 500, and it is possible to access all of them simultaneously.

Serial to Ethernet Connector

To start using Serial to Ethernet Connector, download and install it on a computer that shares a local device (server) and computers that need to access it remotely over network (clients). Launch the app on the server and ‘Share’ a required device, then ‘Connect’ to it from remote computers – the device’s functionality becomes available to network users as it were a local device.

Serial to Ethernet Connector redirects Modbus RTU over TCP/ IP to remote computers. They, in return, display a virtual serial connection through which the software can communicate with the port.

Please note that this Modbus Ethernet converter runs like a Windows service. What does it mean? It means that whenever the system reboots, all connections get reconfigured automatically. The application runs in the background, and you don’t need to keep it open all the time. Another thing we’d like to bring to your attention is that the software can backup a configuration by moving it to another computer – that proves to be really handy at times.

The software is compatible with Windows and Linux operating systems, i.e. you can share a device on a Windows laptop and access it from a Linux desktop, or the other way round. The Linux edition is now available only as a command-line solution. Serial to Ethernet Connector can also be broadcast over UDP.

Serial Port Tunneling

Encapsulate Modbus messages

There is another way to use Modbus over IP or any other network called ‘serial port tunneling’. What you have to do here is to encapsulate a "standard Modbus message" in to a TCP/IP packet or a UDP/IP packet and send it. This method can be used for sending nearly any serial protocol as if it were serial data flow.

However there is a catch here – if you are sending standard Modbus RTU over Ethernet, framing messages might require a while. Unless you have a good control over it, your messages might be split between packages and you will not receive them simultaneously. No content is lost, but because of delay the message won’t be received in a correct way.

To make sure your message is delivered in a single packet, you can use Modbus ASCII instead - this protocol allows you to specify Start of Message and End of Message characters.


You now have been introduced to the Modbus protocol. Users can work with the Modbus RTU over TCP IP protocol, but that does not solve all the issues involved with using Modbus over IP. In some cases, a Modbus RTU to TCP converter will need to be employed. An efficient software application is needed to assist with implementing Modbus RTU over Ethernet. When you need to use Modbus over the Internet, Serial to Ethernet Connector is a software solution that works as a Modbus to TCP IP converter. This application can be used to enact the Modbus RTU over TCP to connect PLCs as well as other electronic industrial equipment. Serial to Ethernet Connector is the most effective way to implement a software Modbus RTU to Ethernet converter.

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