Overview and Applications
Want your Arduino to send a twitter (which can then be easily forwarded to a phone via SMS)? Or grab data from a website? Or serving up sensor data world-wide or even make e-mail notifier. Any of these you can achieve on your stand alone arduino using Arduino ethernet shield.
The Arduino Ethernet shield allows you to connect your Arduino projects to the internet. Simply plug it in to your network (via ethernet cable) and begin talking to the world wide web. It can be programmed to act as a web-server (delivering web pages), or as a client pushing information to a web service (be it twitter or your own website). The possibilities are truly astonishing. and with the onboard SD card-slot can be quite powerful by hosting up full websites.
The Arduino Ethernet shield has a library so you don’t need to think of details how Ethernet chip is controlled. This library allows an Arduino board to connect to the internet. It can serve as either a server accepting incoming connections or a client making outgoing ones. The library supports up to four concurrent connection (incoming or outgoing or a combination).
The ethernet shield adds IP communication, acting as a client or as a server based on the Wiznet W5100 ethernet chip (datasheet) . The most well-known protocols are supported right out of the box, including TCP, UDP and ICMP. Several enthousiasts have added support for even more protocols, such as DHCP and NTP.