Nano V3 Ethernet Shield ? Basic Example ? Web Server

/*
Web server example
(based on standard example by David A. Mellis & Tom Igoe)
(c) 2019 RobotDyn
License: GNU GPL 2.1

A simple web server that shows the value of the analog input pin.

Circuit:
* [Nano V3 Ethernet Shield W5500](https://robotdyn.com/nano-v3-ethernet-shield-w5500-v2.html) (use D10, D11, D12, D13 pins)
* [RobotDyn Nano V3](https://robotdyn.com/nano-v3-atmega-328-usb-ttl-ch340g-micro-usb.html)
* Analog input attached to pin A0
*/

// SPI library
#include <SPI.h>

// Ethernet2 library (support WIZnet W5500 chip)
#include <Ethernet2.h>

// MAC address
byte mac [] = {0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED};

// IP address
IPAddress ip (192, 168, 1, 177);

// Ethernet server on 80 port (default for HTTP)
EthernetServer server (80);

const byte analogPort = 0;

// Setup

void setup() {
// Initialize Serial port
Serial.begin(115200);

// Print start message
Serial.println("Start WEB Server example ...");

// Start Ethernet connection
Ethernet.begin(mac, ip);

// Start HTTP server
server.begin();

// Print IP address
Serial.print("Server at:");
Serial.println(Ethernet.localIP());
} // setup ()

// Functions

void responseHeader(EthernetClient cl) {
// send a standard http response header
cl.println("HTTP/1.1 200 OK");
cl.println("Content-Type: text/html");
cl.println("Connection: close"); // connection close after response
cl.println();
}

void sendPage(EthernetClient cl) {
// Get value of analog input pin
int value = analogRead(analogPort);

// Send Web-page
cl.println("<!DOCTYPE HTML>");

cl.println("<html>");

cl.print("Analog port ");
cl.print(analogPort);
cl.print(" is ");
cl.println(value);

cl.println("</html>");
}

// Server Works

void serverWorks() {
// listen for incoming clients
EthernetClient client = server.available();
if (client) {
Serial.println();
Serial.println("New client");

// an http request ends with a blank line
boolean currentLineIsBlank = true;

while (client.connected()) {
if (client.available()) {

// read character from client
char c = client.read();

// and print to Serial
Serial.write(c);

// if you've gotten to the end of the line (received a newline character)
// and the line is blank,
// the http request has ended, so you can send a reply
if (c == 'n' && currentLineIsBlank) {
// Response (send Web-page)
responseHeader(client);
sendPage(client);
break;
}

if(c == 'n') {currentLineIsBlank = true;}// starting a new line
else if (c != 'r') {currentLineIsBlank = false;} // gotten a character on the current line
} // client.available()
} // client.connected()

delay(1); // give browser time to receive data
client.stop(); // close connection
Serial.println("Client disconnected");
} // if (client)
} // serverWorks()

// Loop

void loop() {
serverWorks();
}