Ethernet Shield allows an Arduino to to connect to the internet and to read and write a microSD card. This shield use Wiznet W5100 ethernet chip. Inside this chip, there are PHY, MAC, IP, and TCP layer. The advantage of using this shield over the ENC28J60 is the TCP/IP stack is already implemented by hardware on this chip. With the ENC28J60 chip the TCP/IP must implemented on the microcontroller that is interfaced to it. In this tutorial, I will explain how to control an LED from PC using this shield.