Hi alagi,
thanks for getting in touch!
So if I understand you correctly, Fronius provides the meter data via Modbus/TCP on Unit-ID 240. If this is true, you should be able to copy the code from the SolarEdge Grid-Meter implementation (https://github.com/OpenEMS/openems/blob/develop/io.openems.edge.solaredge/src/io/openems/edge/solaredge/gridmeter/Config.java).
Regards,
Stefan