Arduino-based Modbus RTU to Modbus TCP/UDP gateway with web interface. Allows you to connect Modbus RTU slaves (such as sensors, energy meters, HVAC devices) to Modbus TCP/UDP masters (such as home automation systems). You can adjust settings through web interface.
For a reliable non-blocking Serial.write we need this is commit in Arduino core to be merged: https://github.com/arduino/Arduino/pull/3737