The Arduino Ethernet shield allows an Arduino board to connect to a LAN using the Ethernet library.

General Information and schematics

Features:

• TCP/IP stack on board provided by the W5100 chip
• Allows the Arduino / Freeduino to access the Internet, as a server or a client
• Very small and efficient Library (Did I say the TCP/IP stack is embedded in the W5100 chip>)
• The shield comes with stackable shields
• Arduino communicates with the shield using SPI (But the complexity of SPI communication is hidden by the Library)

Sample Code

With the following code, the Arduino can access Google and search for "Arduino" and bring the result to the serial port.

#include <Ethernet.h>

byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
byte ip[] = { 10, 0, 0, 177 };
byte server[] = { 64, 233, 187, 99 }; // Google


Client client(server, 80);


void setup()
{
Ethernet.begin(mac, ip);
Serial.begin(9600);


delay(1000);


Serial.println("connecting...");


if (client.connect()) {
Serial.println("connected");
client.println("GET /search?q=arduino HTTP/1.0");
client.println();
} else {
Serial.println("connection failed");
}
}


void loop()
{
if (client.available()) {
char c = client.read();
Serial.print(c);
}


if (!client.connected()) {
Serial.println();
Serial.println("disconnecting.");
client.stop();
for(;;)
;
}
}

This is the official Arduino Ethernet Shield, designed and manufactured by the Arduino team in Italy.