Modbus Gateway for Modbus TCP and RTU Connectivity

April 22, 2024

The Modbus gateway significantly enhances industrial automation by seamlessly connecting Modbus networks with other communication protocols and facilitating smooth data exchange. This technology aligns old systems with the new industrial networks, making IIoT systems highly efficient, reliable, and scalable.

Through familiarization with Modbus protocol basics and Modbus gateways, companies will get an opportunity to gain the upper hand in operation by having new levels of control, monitoring, and data analysis at their fingertips.

Let’s look at the importance, types, and benefits of Modbus gateways in transforming the communication infrastructures of industrial layouts.

What is Modbus?

Modbus stands as a well-established communication protocol in process automation and supervisory control systems. This network architecture was launched by Modicon in 1979 and it was mainly done to develop communication mediators for the client-server interaction between the different types of intelligent devices.

Modbus as a protocol facilitates the data exchange between the digital plant expressed through plug-and-play devices, which help achieve process efficiency and control flexibility. This protocol is widely adopted in industrial environments, and stands out due to its low operational and maintenance complexity, making it a preferred choice. Modbus supports either serial lines, Ethernet, or IP protocol suites for passing data between individual devices with a computer. This protocol allows the devices to connect to a single network and communicate with each other through a computer. 

The most commonly used is the supervisory computer for the supervisory control and data acquisition system that links to the remote terminal unit. Modbus comes in three kinds: the Modbus RTU, the Modbus ASCII, and the Modbus TCP. They are designed to fit a specific communication scenario.

Modbus is significant for its widespread usage as a communication protocol for industrial systems. It is one of the main communication protocols used in the automation and control industries, and it is used for interconnecting various devices like PLCs, sensors, and actuators.

Modbus is also widely used in IoT platforms to connect and manage IoT devices. By connecting Modbus devices to the IoT platform, users can benefit from centralized management, secure data collection and storage, real-time monitoring and alerting, remote device control and configuration, and easy integration with other IoT devices and applications. Read our connecting Modbus devices to the KaaIoT platform a step-by-step guide to make this process smoother. With the KaaIoT platform, you gain centralized control, secure data management, real-time monitoring, and the ability to integrate with other IoT devices.

Modbus RTU vs TCP

The straightforward response to this frequently asked question is: No. While they are interconnected and exhibit some similarities, the physical layer or interface (as noted at the outset of this article) remains distinct from the protocol and can thus vary. Specifically, one employs RTU (Remote Terminal Unit), while the other utilizes TCP (Transmission Control Protocol).

In Modbus RTU, the physical layer functions as a serial communication protocol employing a binary data representation. Although various standard transports exist, RS232 and RS485 are the most prevalent. RS232 preceded RS485, introduced to facilitate longer distances, increased speeds, and the ability to signal multiple devices. Modbus RTU employs a client-server architecture, wherein a single client device issues commands to one or more server devices, eliciting responses with data. Widely supported by legacy devices, Modbus RTU finds application in industrial automation, building control systems, and other contexts requiring long-distance communication.

Modbus TCP (also referred to as Modbus IP and Modbus TCP/IP) utilizes TCP/IP networking to facilitate communication between Modbus devices. It extends the functionality of Modbus RTU for use over Ethernet or other IP-based networks. Modbus TCP commonly serves to connect Modbus devices over extended distances or to integrate Modbus networks with diverse network types. Unlike Modbus RTU, the more contemporary Modbus TCP accommodates multiple clients (devices initiating and controlling communication with servers) and supports the transmission of parameters such as point name, resolution, and units. Modbus TCP predominates in enterprise-level applications, IoT contexts, or large-scale applications where relatively newer devices capable of network connectivity are employed.

Modbus RTU gateways, as well as Modbus TCP gateways, prove particularly valuable in scenarios where compatibility issues may arise due to Modbus's extensive usage and its application across diverse hardware and software configurations. These gateways are essential for integrating disparate systems.

4 Modbus gateway types

The Modbus gateways are essential devices that facilitate the conversion between different Modbus protocols, enabling seamless communication between various devices in industrial settings. A key component of IoT (Internet of Things) systems, these gateways play a crucial role in ensuring smooth and reliable data exchange between devices operating on different Modbus protocols.

For more information on IoT gateways, please refer to our article "What is an IoT Gateway?".

There are four main types of Modbus gateways, each catering to specific communication needs:

  • Modbus RTU to Modbus TCP Gateway: This gateway enables communication between devices operating on Modbus RTU and Modbus TCP protocols.
  • Modbus TCP to Modbus RTU Gateway: This gateway enables communication between devices operating on Modbus TCP and Modbus RTU protocols.
  • Modbus RTU to Ethernet Gateway: This gateway enables communication between devices operating on Modbus RTU and Ethernet protocols.
  • Modbus TCP to Ethernet Gateway: This gateway enables communication between devices operating on Modbus TCP and Ethernet protocols.

Benefits of Modbus gateway

Benefits of modbus gateway

Protocol translation

Protocol translation converts data between Modbus, typically used in industrial automation systems and other communication protocols. This translation enables devices operating on different protocols to communicate with each other effectively. For example, a Modbus gateway can translate Modbus RTU data into Modbus TCP/IP or other protocols such as Ethernet/IP, Profinet, or MQTT, allowing interoperability between legacy Modbus devices and modern industrial networks or IoT platforms.

Legacy system compatibility

Legacy system compatibility refers to the capacity of a technology or solution to smoothly integrate with and support older, pre-existing systems, commonly known as legacy systems. These systems may include devices such as programmable logic controllers (PLCs), sensors, actuators, and other industrial equipment that communicate using the Modbus protocol. As industries evolve and adopt new technologies, there is a need to integrate these legacy Modbus systems with modern industrial networks or IoT platforms.

Enhanced monitoring and control

Enhanced monitoring and control offer operators precise oversight, efficiency, and adaptability. Real-time data monitoring allows operators to gain instant access to important information, facilitating proactive decision-making and swift issue resolution. Centralized management streamlines operations, enabling operators to efficiently monitor and control diverse devices from a single interface. Remote access capabilities enhance operational flexibility, allowing operators to manage processes from anywhere with an internet connection.

Reduced downtime

With the ability to quickly diagnose and troubleshoot communication issues, Modbus gateways minimize downtime and ensure continuous operations in industrial environments. By providing real-time insights into network performance and device connectivity, these gateways enable operators to identify and address communication issues, reducing the risk of production interruptions and equipment failures. Modbus gateways streamline maintenance and repair processes by facilitating remote access to devices and systems, allowing technicians to diagnose problems, apply fixes, and perform updates without the need for physical intervention.

Improved data management

By facilitating bi-directional data exchange between different devices and systems, Modbus gateways serve as a conduit for seamless integration and interoperability within industrial environments. This enables efficient data collection with analysis and opens avenues for advanced functionalities such as predictive maintenance, machine learning-based optimization, and real-time monitoring and control.

Modbus gateway applications

These applications demonstrate the versatility and importance of Modbus gateways in various industries, ranging from renewable energy systems like solar power to industrial automation, remote monitoring, and smart manufacturing processes.

Let’s take a look at the examples of Modbus gateway applications.

Monitoring solar power systems

Modbus gateways monitor the performance of solar panels, inverters, battery systems, and metering systems connected to the same solar network, enabling real-time monitoring and control of critical equipment in solar installations.

Industrial automation and building control systems

Modbus gateways find extensive use in industrial automation and building control systems, where they facilitate communication between legacy devices supporting Modbus RTU and modern devices using Modbus TCP/IP, ensuring seamless data exchange and system integration.

SCADA system integration

Modbus gateways are important links between SCADA iot systems and various devices, facilitating access to internal memory. They act as bridges, enabling seamless communication between devices using Modbus TCP and Modbus RTU protocols. For instance, the uPAC-7186/I-7188 Modbus Gateway from ICP DAS is used to connect a supervisory computer with a remote terminal unit (RTU) in SCADA systems. The Modbus gateway enables the communication between the SCADA system and the RTU, allowing for the collection and analysis of data for monitoring and control purposes.

Smart manufacturing processes

Modbus gateway is an important component in smart manufacturing by enabling communication with PLCs, reading, sending, and connecting data to various sources like databases and custom applications, facilitating informed decision-making and efficient manufacturing processes.


In conclusion, Modbus gateways stand out as important components in industrial automation. They bridge the gap between traditional Modbus protocol and contemporary communication needs. They offer invaluable benefits such as seamless protocol translation, legacy system integration, enhanced monitoring, and reduced system downtime. With four main types of gateways available, Modbus devices cater to specific networking requirements, ensuring businesses can leverage their existing infrastructures while embracing modern IoT capabilities.