Connecting the Arduino to networks obviously brings the Internet to mind. We could try to create a small system that can send messages over the Internet. I choose to use the micro-blogging service Twitter because it provides a nice communication API.
We are going to use the same circuit that we used in the Wiring Arduino to wired Ethernet section except that here we are using the Arduino MEGA related to some memory constraints with a smaller board.
API stands for Application Programming Interface. Basically, it defines ways to exchange data with the considered system. We can define APIs in our systems in order to make them communicate with others.
For instance, we could define an API in our Arduino firmware that would explain how and what to send in order to make the LED on the board switch on and off. We won't describe the whole firmware, but we would provide to the world a basic document explaining precisely the format and data to send from...