But when I compile it for the ESP8266 board I got tons of errors around the SPI.h calls.
I understand that the ESP8266 does have anything to do with the SPI lib.
But how do I overcome this problem?
The Arduino "Ethernet library" supports the Wiznet W5100 chip only.
It does NOT support any other Ethernet chip, but only the Wiznet W5100.
The Arduino "SPI library" supports the SPI interface on Arduino boards only.
It does NOT support SPI interfaces on any other device, but only SPI on Atmega-Controllers