Ethernet Shield enables us to connect Arduino to an ethernet network and build projects which send and receive information via local network and internet. The device, along with its control library, allows the design of network applications easily. There is no need to worry about the complicated signaling schemes in ethernet networks since all control and connection are made by library routines. After the connection is established, we may just read or write data through it, similarly to a conventional serial connection.
In the following, we show an example of a project of a web page that allows you to turn on or turn off a digital port of the Arduino via the local network or the internet. In a practical application, the project could be used to control a lamp, serving as a good “Hello World” application for home automation with Arduino. In this example, the idea is to focus on the design of the software required for the application so that we will consider the connection of led to the Arduino port and show one of the most expensive ways to light a led.