RFID based Attendance System

#include <SPI.h>
#include <Wire.h>
#include <MFRC522.h>
#include <MFRC522Extended.h>
#include <ESP8266WiFi.h>
#include <ESP8266HTTPClient.h>


#define SS_PIN D4
#define RST_PIN D3

MFRC522 mfrc522(SS_PIN,RST_PIN);

const char* NAME; // variable to save the name of the person


char* response = " ";
String res = "";
char* succ_code = "200 OK";

//Necessary parameters for IFTTT request
String Event_Name = "rfid";
String key = "kjAPKzVS3HifS4sMFHxjEBdqod3JevEQz_4v0-7yy0d";
String resource = "/trigger/" + Event_Name + "/with/key/" + key;
const char* server = "maker.ifttt.com";

//Provide your WiFi Credentials
const char* ssid = "Giant Infosys_2.4";
const char* password = "Giant#123#456";



void setup() {
  Serial.begin(9600);
  SPI.begin();
  mfrc522.PCD_Init();


    // Connect to Wi-Fi
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.println("Connecting to WiFi..");
  }

  // Print ESP32 Local IP Address
  Serial.print("WiFi connected in ");
  Serial.print(millis());
  Serial.print(",");
  Serial.println(WiFi.localIP());


}

void loop() {
  Serial.println("Scan tag");
  Serial.println("Waiting for the tag1");

      if ( ! mfrc522.PICC_IsNewCardPresent())
      {
        return;
      }
      // Select one of the cards
      if ( ! mfrc522.PICC_ReadCardSerial())
      {
        return;
      }


      String content = "";
      byte letter;
      Serial.println(mfrc522.uid.size);
      for (byte i = 0; i < mfrc522.uid.size; i++)
      {
        //Serial.print(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " ");
        //Serial.print(mfrc522.uid.uidByte[i], HEX);
        content.concat(String(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " "));
         Serial.println(content);
        content.concat(String(mfrc522.uid.uidByte[i], HEX));
      }
      Serial.println(content);
      content.toUpperCase();
      Serial.println("Waiting for the tag2");

      if (content.substring(1) == "E9 E2 8B A3") //change here the UID of the card that you want to give access
      {
        Serial.print("!!--");
        Serial.println(content.substring(1));
        NAME = "Aayush";
        delay(1000);

        makeIFTTTRequest(); // Making Registrations on Google Sheet via IFTTT
      }

      else if (content.substring(1) == "C9 B2 AE 82") //change here the UID of the card that you want to give access
      {
        Serial.print("!!--");
        Serial.println(content.substring(1));
        NAME = "Harsh";
        makeIFTTTRequest(); // Making Registrations on Google Sheet via IFTTT

      }

      else
      {
        Serial.println("Not Registered");

      }

     content.substring(1) = "";

}




void makeIFTTTRequest(){

    HTTPClient http;
    Serial.print("Connecting to ");
    Serial.print(server);

    WiFiClient client;
    int retries = 5;
    while (!!!client.connect(server, 80) && (retries-- > 0)) {
      Serial.print(".");
    }
    Serial.println();
    if (!!!client.connected()) {
      Serial.println("Failed to connect...");
    }

    Serial.print("Request resource: ");
    Serial.println(resource);

    String jsonObject = String("{\"value1\":\"") + NAME + "\"}";

    client.println(String("POST ") + resource + " HTTP/1.1");
    client.println(String("Host: ") + server);
    client.println("Connection: close\r\nContent-Type: application/json");
    client.print("Content-Length: ");
    client.println(jsonObject.length());
    client.println();
    client.println(jsonObject);

    int timeout = 5 * 10; // 5 seconds
    while (!!!client.available() && (timeout-- > 0))
    {
      delay(100);
    }
    if (!!!client.available())
    {
      Serial.println("No response...");
    }

    while (client.available())
    {
      // Serial.write(client.read());
      char add = client.read();
      res = res + add;
    }
    response = &res[0];
    Serial.println("=======");
    Serial.println(response);

    if (strstr(response, succ_code)) // If connected to internet, make registration
    {
      Serial.println("Registered");
      Serial.println(("Registered"));
      delay(1000);
    }

    else // If not connected to internet, don't make registration
    {
      Serial.println("Not Registered");

      delay(1000);
    }
    response = "";
    res = "";
    Serial.println("\nclosing connection");
    client.stop();


  }