Client_checker is wrapped in if statement because i stopped right there its not a finished code. There is no need for now to call for other functions.
Didnt get whats wrong with using _ ?
Thanks for suggestion will follow to learn memcmp.
For loop is fast but you didnt noticed delay() i guess. Besides this loop was tested via serial monitor even with sending very long strings char array was arranged properly from position [0] to the length of the string. C=(receivecommand()) dont know why put extra parentheses but its not changing property of that function even if i will add 100 of opening and closing parentheses.
int memcmp (const void *a1, const void *a2, size_t size). My array is not const how to use with memcmp?