The Espressif ESP-Modbus Library (esp-modbus) supports Modbus communication in the networks based on RS485, Wi-Fi, Ethernet interfaces. The ESP-IDF component freemodbus has been moved from ESP-IDF since version v5.0 to a separate repository:
The documentation can be found on the link below:
The examples below demonstrate the ESP-Modbus library of serial, TCP ports for slave and master implementations accordingly.
Please refer to the specific example README.md for details.
https://modbus.org/specs.php: Modbus Organization with protocol specifications.