* arduino-cli compile --fqbn arduino:mbed_opta:opta examples/opta_opcua_server -v --build-property compiler.cpp.extra_flags="-DUSE_MODBUS_SENSOR_MD02=1" -u -p /dev ...
return ""; // if not handeled above then let the HTTP server send the reply itself (server files stored in /var/www/html directory or send 404 reply) ...