Qt Modbus

Modbus is a request/reply protocol that has one Modbus client in its network and may have many Modbus servers. Servers can control only their own internal states and clients can read and write data in them. Modbus is not restricted by the network type, in theory it can use any QIODevice. However, not every plugin supports all classes derived from QIODevice.

Each Modbus server has four tables in which it can store data.

name data range in one field permissions for client
Discrete Inputs 0-1 Read
Coils 0-1 Read/Write
Input Registers 0-65535 (0xffff) Read
Holding Registers 0-65535 (0xffff) Read/Write

The Modbus API provides some common API to access the Modbus devices:

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Licensed under the GNU Free Documentation License, Version 1.3.
https://doc.qt.io/qt-5.12/qtmodbus-backends.html