the Ethernet module W5100 To establish an internet connection, it is a single-chip, full-featured, internet-enabled module. This module, in basic terms, allows the Arduino board to connect to the internet. We can finish the internet connection without the need of an operating system if we use this module. TCP, PPPoE, Ethernet, UDP, ICMP, IPv4, and other hardwired TCP/IP protocols are also supported. It can operate in both full-duplex and half-duplex modes. It can handle up to four simultaneous socket connections and ADSL connections. the supply voltage is 5V with Signal levels 3.3V and 5V tolerant and the Dimensions of the board are 54 x 30 x 17mm.

Ethernet Module W5100 Specifications:

• Supports 10/100 Base-TX
• Supports half/full-duplex operation
• Supports auto-negotiation and auto cross-over detection
• IEEE 802.3/802.3u Compliance
• Operates 3.3V with 5V I/O signal tolerance
• Supports network status indicator LEDs
• Includes Hardware Internet protocols: TCP, IP Ver.4, UDP, ICMP, ARP, PPPoE, IGMP
• Includes Hardware Ethernet protocols: DLC, MAC
• Supports 4 independent connections simultaneously
• Supports MCU bus Interface and SPI Interface
• Supports Direct/Indirect mode bus access
• Supports Socket API for easy application programming
• Interfaces with two 2.54mm pitch 2 x 10 header pin
• Temperature : 0 ~ 70℃ (Operation), -40 ~ 85℃ (Storage)

This board is compatible with the Arduino IDE's Ethernet Library. This library is compatible with a wide range of Arduino Ethernet Shields and modules, including W5200/W5500-based devices as well as W5100-based devices. An Arduino board may connect to the Internet using this library. The board may act as both a server and a client, receiving incoming connections and sending them out. The library supports up to eight concurrent connections (W5100 and boards with less than 2 kB SRAM are limited to four) (incoming, outgoing, or a combination).

The SPI bus is used to communicate between the Arduino board and the shield. On the Uno, this is digital pins 11, 12, and 13; on the Mega, it's pins 50, 51, and 52. Pin 10 is utilized as SS on both boards. The hardware SS pin, 53, is not used to choose the Ethernet controller chip on the Mega, but it must be left as an output or the SPI interface would fail. An Arduino board may connect to the Internet using this library. The board may act as both a server and a client, receiving incoming connections and sending them out.

This is How to connect the Ethernet W5100 Module with Arduino UNO:

 The circuit is made of an Arduino Nano and an Ethernet Module W5100 (This project would be possible with Ethernet Arduino Shield and Arduino UNO as well). The Arduino and Ethernet modules are connected as indicated in the circuit diagram.

Connect the Arduino Nano's 5V and GND pins to the +5 and G pins of the Ethernet Module, respectively (These connections supply power to the Ethernet Module).

Connect Arduino pins 9, 10, 11, 12, and 13 to the Ethernet module's R, SS, MO, MI, and CK (These make the communication between Arduino and Ethernet over SPI).

Code for Ethernet W5100 Module to Control an Led with Web page:

#include  //protocol to communaicate to the ethernet module
#include  //library to run webclient / web server over ethernet
byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED }; //physical mac address set to the ethernet module
/*the number 0 in the IP address depends on the host of the network you are connected to, check that by doing ipconfig on command prompt*/
byte ip[] = { 192, 168, 0, 12 }; // IP address in LAN – need to change according to your Network address
byte gateway[] = { 192, 168, 0, 12 }; // internet access via router
byte subnet[] = { 255, 255, 255, 0 }; //subnet mask
EthernetServer server(80); //port where the server can be accessed
String readString; // to read the response form the user / client
int ledPin = 2; // Led is connected to pin 2
void setup(){
    pinMode(ledPin, OUTPUT); //pin selected to control
    //start Ethernet
    Ethernet.begin(mac, ip, gateway, subnet); //initialize ethernet
    server.begin(); //start the server
}
void loop(){
    // Create a client connection
    EthernetClient client = server.available();
    //check if someone is tried access the assigned IP address over a browser
    if (client) {
      //if connected, continue checking if client is sending some message back to the server
        while (client.connected()) {
            if (client.available()) {
                char c = client.read();             
                //read char by char HTTP request
                if (readString.length() < 100) {
                    //store characters to string
                    readString += c;
                }
                //if HTTP request has ended– 0x0D is Carriage Return \n ASCII
                if (c == 0x0D) {
                  //display the webpage
                    client.println("HTTP/1.1 200 OK"); //send new page
                    client.println("Content-Type: text/html");
                    client.println();
                    client.println("");
                    client.println("");
                    client.println("");
                    client.println("");
                    client.println("");
                    client.println("
");
                    client.println("
ARDUINO ETHERNET LED CONTROL
");
                    client.println("
");
                    client.println("
");
                    //creating a link to redirect the user to turn on the light
                    client.println("
Turn On LED
");
                    //creating a link to redirect the user to turn off the light
                    client.println("
Turn Off LED
");
                    client.println("
");
                    client.println("");
                    client.println("");
                    delay(10);
                    //stopping client
                    client.stop();
                    // control arduino pin with URL
                    if(readString.indexOf("?LEDON") > -1) //checks for LEDON
                    {
                        digitalWrite(ledPin, HIGH); // set pin high
                    }
                    else{
                        if(readString.indexOf("?LEDOFF") > -1) //checks for LEDOFF
                        {
                            digitalWrite(ledPin, LOW); // set pin low
                        }
                    }
                    //clearing string for next read
                    readString="";
                }
            }
        }
    }
}