Ok, I untherstand perfectly how use a MODBUS.
Please, I hope you make questions before responds incorrectly.
This solution not use a MODBUS, so e need use a multiple unicasting.
1.- The device RUT receive data over RS-232.
2.- The device RUT needs send the data received over RS232 to multiples IP addresses.
2.1- Is necesary stablish or indicate to device RUT the remotess IPs addresses.
3.- The app can't send to multiples IP addresses.
If you needs learn more about multiple unicasting, please read here.
Thank you for your support.