Modbus TCP

Modbus is a long-living communication standard in industrial automation. It has been developed to communicate via TCP and meeting security needs.

There are different Modbus implementations available, e.g. as a function block (available in the PLCnext Store). But using a function block, its instantiation is necessary for each and every Modbus connection, and also for each and every function code (FC) call. Therefore, when working within a larger structure that gets confusing and exhausting for developers.

There are already some other custom implementations, some programmed in high-level languages, that are more convenient to use in development. 

From firmware release 2024.6 on, there is a Modbus TCP Client and from firmware release 2026.0 LTS on, there is a Modbus TCP Server directly implemented into the Automation Runtime Platform (ARP) of PLCnext Technology.

This Modbus TCP Client and the Modbus TCP Server can be configured via the PLCnext Engineer programming software. The implementation depends on the libmodbus open source library, provided by libmodbus.org.

Here you will find a description to