The NODA Modbus Gateway Addon can communicate with Modbus devices over either Modbus TCP (Ethernet) or Modbus RTU (RS-485).

The solution uses the same protocol over MQTT as the NODA Modbus Gateway.

Modbus TCP

Communication with any Modbus TCP compatible Modbus Slave is possible over any port.

See the Setup section for more details about configuring the Modbus TCP support.

Modbus RTU

The communication protocol does not support specifying an RS-485 target. Instead, only IP targets are supported.

To get around this limitation, the NODA Modbus Gateway Addon assigns special meaning to the IPv4 loopback addresses. The loopback address of is used as a way to forward a request to the RS-485 interface. The TCP port (typically 502) is silently ignored in such a request.

See the Setup section for more details about how to configure the RS-485 support.