esp arduino

#include <ESP8266WiFi.h>
#define LED_PIN 16

const char* ssid = "*****";
const char* password = "******";
int state = 0;
WiFiServer server(80); //Initialize the server on Port 80

void setup()
{
 Serial.begin(115200); //Start communication between the ESP8266-12E and the monitor window
 delay(10);

 pinMode(LED_PIN, OUTPUT); //GPIO16 is an OUTPUT pin;
 digitalWrite(LED_PIN, LOW); //Initial state is ON

 WiFi.begin(ssid, password); // Provide the (SSID, password);
 while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("");
  Serial.println("WiFi connected");
 server.begin(); // Start the HTTP Server

 //Looking under the hood
 Serial.print("Server IP is: "); // Print the IP to the monitor window
 Serial.println(WiFi.localIP());
}

void loop()
{
 WiFiClient client = server.available();
 if (!client)
 {
  return;
 }
 //Looking under the hood
 Serial.println("Somebody has connected :)");

 //Read what the browser has sent into a String class and print the request to the monitor
 String request = client.readStringUntil('\r');
//Looking under the hood
 Serial.println(request);
 // Handle the Request
 if (request.indexOf("/OFF") != -1)
 {
  digitalWrite(LED_PIN, HIGH);
  Serial.println(request.indexOf("/ON"));
 }
 else if (request.indexOf("/ON") != -1)
 {
  digitalWrite(LED_PIN, LOW);
  Serial.println(request.indexOf("/OFF"));
 }
 if (request.indexOf("/Green_BT") == 4)
 {
  if(state !=0)
  {
   state = 0;
   Serial.println("Turn OFF");
  }
  else
  {
   state = 1;
   Serial.println("Turn ON");
  }
  Serial.println("Green is pressed");
  Serial.println(request.indexOf("/Green_BT"));
 }
 Serial.println(request.indexOf("/name_field"));

 //Prepare the HTML document to respond and add buttons:
 String s = "HTTP/1.1 200 OK\r\n";
 s += "Content-Type: text/html\r\n\r\n";
 s += "<!DOCTYPE HTML>\r\n<html>\r\n";

 s += "<style> .button { background-color: #4CAF50; border: none; color: white; padding: 16px 32px; text-align: center; text-decoration: none; display: inline-block;mfont-size: 16px; margin: 4px 2px; -webkit-transition-duration: 0.4s; transition-duration: 0.4s; cursor: pointer;}";
 s += " .button1 { background-color: #4CAF50; color: white; border: 2px solid #4CAF50;}";
 s += " .button1:hover { background-color: white; color: black;}";
 s += "</style>";

 s += "<br><input type=\"button\" name=\"b1\" value=\"Turn LED ON\" onclick=\"location.href='/ON'\">";
 s += "<br><br><br>";
 s += "<input type=\"button\" name=\"b1\" value=\"Turn LED OFF\" onclick=\"location.href='/OFF'\">";
 s += "<br><br><br>";
 s += "<button class=\"button button1\" onclick=\"location.href='/Green_BT'\">Green</button>";
 s += "<br><br><br>";
 s += "<form action=\"/team_name_url/\" method=\"post\">";
 s += "<label for=\"team_name\">Enter name: </label>";
 s += "<input id=\"team_name\" type=\"text\" name=\"name_field\" placeholder=\"Default name for team.\">";
 s += "<input type=\"submit\" value=\"OK\">";
 s += "</form>";
 s += "</html>\n";

 //Serve the HTML document to the browser.
 client.flush(); //clear previous info in the stream
 client.print(s); // Send the response to the client
 delay(1);
 Serial.println("Client disonnected"); //Looking under the hood
}