Already I guess. The file whose name is transmitted through the socket from the client to the server does not open. Everything is transmitted correctly, if any newline is added. Maybe you need to remake from
char into a string?
char buffer; ....(тут recv через сокет), в буфере при отладке "С:/6.pro" FILE *in = fopen(buffer, "r"); if(in == NULL) printf("Error opening file"); else printf("File was successfully opened");