Need Help to implement MODBUS TCP Master over Atmega32 MCU I am doing a project where I have to interface with Fronius Solar Inverter with Atmega32 MCU over MODBUS TCP. I want to set the MCU as client and The inverter as Server and I have to implement two MODBUS Function only these are READ_HOLDING_REGISTER and WRITE_SIGLE_REGISTER and Function Code are 0x03 and 0x06 respectively.  I am newbie in this field and dont know about networking. Please anybody help me How can I develop the Software in C for this purpose?? 

The Document of Fronius Inverter for MODBUS TCP is Fronius MODBUS TCP Datamanger
So if you want to the atmega as client this means it will start the conection and made the request for values, so translating into modbus words your atmega will be a modbus master and the solar will be a modbus slave.

first you need a way to interface the micocontroller to the tcp/ip stack. you can use an ic or arduino shield which has this ic like a w5100 or enc28j60.

then you can write a library over tcp sockets to start the comunication or change some from the arduino.

https://www.google.com.br/url?sa=t&amp;source=web&amp;rct=j&amp;url=http://myarduinoprojects.com/modbus.html&amp;ved=0ahUKEwj9zMvjiYDTAhXJkpAKHfsNBz0QFggpMAE&amp;usg=AFQjCNEfRhDgPGJNK-IUqrUw1FXEnBcxwQ&amp;sig2=Xs0JNEWi_F_XiPgkTQdy-w