server + LED - Wokwi ESP32, STM32, Arduino Simulator

#include <WiFi.h>
#include <LiquidCrystal_I2C.h>

#define NTP_SERVER "pool.ntp.org"
#define UTC_OFFSET 3600
#define UTC_OFFSET_DST 3600

#define blue 18
#define green 23
#define red 19

struct tm cas;

const int cervena = 0;
const int zelena = 1;
const int modra = 2;
const int reset = 3;

int farba = reset;

// Server running on port 80
WiFiServer server(80);

LiquidCrystal_I2C lcd(0x27, 16, 2);

String header;
unsigned long currentTime = millis();
unsigned long previousTime = 0;
const long timeoutTime = 2000;

void setup() {
  Serial.begin(9600);
  lcd.init();
  lcd.backlight();

  pinMode(blue, OUTPUT);
  pinMode(green, OUTPUT);
  pinMode(red, OUTPUT);

  WiFi.begin("soc2019", "socka2019");
  while (WiFi.status() != WL_CONNECTED) {
    delay(250);
    Serial.print(".");
  }
  Serial.println("\nWiFi úspešne pripojená!");
  Serial.print("IP adresa: ");
  Serial.println(WiFi.localIP());

  server.begin();

  configTime(UTC_OFFSET, UTC_OFFSET_DST, NTP_SERVER);
}

void loop() {
  WiFiClient client = server.available();
  if (client) {
    Serial.println("Novy klient");
    currentTime = millis();
    previousTime = currentTime;
    String currentLine = "";

    while (client.connected() && (currentTime - previousTime <= timeoutTime)) {
      currentTime = millis();
      if (client.available()) {
        char c = client.read();
        Serial.write(c);
        header += c;

        if (c == '\n') {
          if (currentLine.length() == 0) {

            client.println("HTTP/1.1 200 OK");
            client.println("Content-type:text/html");
            client.println("Connection: close");
            client.println("");

            if (header.indexOf("GET /2/cervena") >= 0) {
              digitalWrite(red, HIGH);
              digitalWrite(green, LOW);
              digitalWrite(blue, LOW);
              farba = cervena;
              lcd.setCursor(0, 0);
              lcd.print("Cervena      ");
            } else if (header.indexOf("GET /2/zelena") >= 0) {
              digitalWrite(red, LOW);
              digitalWrite(green, HIGH);
              digitalWrite(blue, LOW);
              farba = zelena;
              lcd.setCursor(0, 0);
              lcd.print("Zelena       ");
            } else if (header.indexOf("GET /2/modra") >= 0) {
              digitalWrite(red, LOW);
              digitalWrite(green, LOW);
              digitalWrite(blue, HIGH);
              farba = modra;
              lcd.setCursor(0, 0);
              lcd.print("Modra   ");
            } else if (header.indexOf("GET /2/reset") >= 0) {
              farba = reset;
              digitalWrite(red, LOW);
              digitalWrite(green, LOW);
              digitalWrite(blue, LOW);
              vypisCas();
            }

            // HTML Response
            client.println("<!DOCTYPE html><html>");
            client.println("<head><title>ESP32 Web Server</title>");
            client.println("<style>");
            client.println("body { font-family: Arial; text-align: center; margin: 20px; }");
            client.println(".button { padding: 10px 20px; text-decoration: none; color: white; border-radius: 5px; }");
            client.println(".button-zelena { background-color: green; }");
            client.println(".button-cervena { background-color: red; }");
            client.println(".button-modra { background-color: blue; }");
            client.println(".button-reset { background-color: gray; }");
            client.println("</style></head>");
            client.println("<body>");
            client.println("<h1>ESP32 Web Server</h1>");

            client.print("<p>Farba: ");
            if (farba == cervena) {
              client.println("<span style='color:red;'>Cervena</span></p>");
            } else if (farba == zelena) {
              client.println("<span style='color:green;'>Zelena</span></p>");
            } else if (farba == modra) {
              client.println("<span style='color:blue;'>Modra</span></p>");
            } else {
              client.println("<span style='color:gray;'>RESET</span></p>");
            }

            client.println("<p><a href=\"/2/cervena\" class=\"button button-cervena\">Cervena</a></p>");
            client.println("<p><a href=\"/2/zelena\" class=\"button button-zelena\">Zelena</a></p>");
            client.println("<p><a href=\"/2/modra\" class=\"button button-modra\">Modra</a></p>");
            client.println("<p><a href=\"/2/reset\" class=\"button button-reset\">Reset</a></p>");
            client.println("</body></html>");
            client.println("");
            break;
          } else {
            currentLine = "";
          }
        } else if (c != '\r') {
          currentLine += c;
        }
      }
    }
    header = "";
    client.stop();
    Serial.println("Klient je odpojeny.");
  }
}

void vypisCas() {
  if (!getLocalTime(&cas)) {
    Serial.println("PROBLEM SO ZISKANIM UDAJOV ZO SERVERU!");
    lcd.setCursor(0, 1);
    lcd.print("Cas nedostupny");
    return;
  }
  lcd.setCursor(0, 0);
  lcd.print("RESET   ");
  lcd.setCursor(0, 1);
  lcd.printf("Cas: %02d:%02d:%02d", cas.tm_hour, cas.tm_min, cas.tm_sec);
}