Need Help to implement MODBUS TCP Master over Atmega32 MCU
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