Arduino Webserver with ENC28J60

From the prehistory: an Arduino Uno with ENC28J60 Etherrnet card, serving a webpage. Just out of nostalgia if someone needs it

#include <UIPEthernet.h> // Library for ENC28J60 Ethernet shield
#include <OneWire.h>     // Library for OneWire communication
#include <DallasTemperature.h> // Library for DS18B20 temperature sensor

// Pin where the DS18B20 is connected
#define ONE_WIRE_BUS 2
OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);

EthernetServer server(80); // Ethernet server on port 80

void setup() {
  // Start the serial communication for debugging
  Serial.begin(9600);

  // Set up the Ethernet shield with a fixed MAC address and IP address
  byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED }; // MAC address
  IPAddress ip(192, 168, 1, 177); // Local IP address (adjust as needed for your network)

  // Start the Ethernet and the server
  Ethernet.begin(mac, ip);
  server.begin();
  Serial.print("Server is at ");
  Serial.println(Ethernet.localIP());

  // Start the temperature sensor
  sensors.begin();
}

void loop() {
  // Check for incoming client connections
  EthernetClient client = server.available();
  if (client) {
    Serial.println("New client");

    // Wait for data from the client
    boolean currentLineIsBlank = true;
    while (client.connected()) {
      if (client.available()) {
        char c = client.read();

        // If the request is complete (double newline), send the response
        if (c == '\n' && currentLineIsBlank) {
          // Get the temperature reading
          sensors.requestTemperatures(); // Request temperature
          float temperature = sensors.getTempCByIndex(0); // Get temperature in Celsius

          // Send the HTTP response headers
          client.println("HTTP/1.1 200 OK");
          client.println("Content-Type: text/html");
          client.println("Connection: close"); // The connection will close after this response
          client.println();

          // Send the HTML content
          client.println("<!DOCTYPE HTML>");
          client.println("<html>");
          client.println("<h1>Temperature Monitor</h1>");
          client.print("<p>Temperature: ");
          client.print(temperature);
          client.println(" °C</p>");
          client.println("</html>");
          break;
        }

        if (c == '\n') {
          currentLineIsBlank = true;
        } else if (c != '\r') {
          currentLineIsBlank = false;
        }
      }
    }

    // Close the connection with the client
    client.stop();
    Serial.println("Client disconnected");
  }
}

This sketch initializes the Ethernet shield with a given MAC address and IP address. Adjust the IP address as needed for your network.
The OneWire library is used to communicate with the DS18B20 temperature sensor, and the DallasTemperature library is used to read the temperature in Celsius.
The Ethernet server listens on port 80 for incoming HTTP requests.
When a client connects, the sketch reads the incoming data and responds with a simple HTML page showing the temperature in degrees Celsius.
The sketch handles client connections by waiting for a complete HTTP request and then sending the temperature reading in the response.

To use this sketch, make sure you have installed the UIPEthernet, OneWire, and DallasTemperature libraries. You can install them via the Arduino Library Manager. Adjust the IP address and MAC address as needed to fit your network configuration.