If you find it difficult to write in english use google-translate.
Write down in detail what you want to say in your native language and let do google-translate the translation. google-translate "knows" a lot of languages even madarin, Urdu, Xhosa, Paschtu etc.
I'm not familiar with modbus tcp/ip. Did you analyse a modbus tcp-IP-demo-code?
I guess it expects data to be send as bytes. But this is just a quick guessing without knowing it.
best regards Stefan