ESP8266 ThingSpeak Temperature Client

#include <OneWire.h>
#include <DallasTemperature.h>
#include <ESP8266mDNS.h>
#include <ESP8266WiFi.h>

#define ALLOWED_CONNECT_CYCLES 40
#define ALLOWED_READ_CYCLES 80
#define ONE_WIRE_BUS 2  // DS18B20 pin
OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature DS18B20(&oneWire);

/*
 * Update those 3 line to configure WiFi and ThingSpeak project
 */
const String apiKey = "[THINGSPEAK_API_KEY_GOES_HERE]";
const String wifiSSID = "[WIFI_NETWORK_SSID_GOES_HERE]";
const String wifiPassword = "[WIFI_NETWORK_PASSWORD_GOES_HERE]";

#define SLEEP_TIME_SECONDS 900 //900 for 15 minutes

const char* host = "api.thingspeak.com";

void setup() {

  /* 
   *  If after changing WiFi settings (SSID or password) ESP8266
   *  does not want to connect again, uncomment this line and reflash
   */
  //ESP.eraseConfig();
  
  WiFi.begin(wifiSSID, wifiPassword);
  
  uint8_t counter = 0;
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    counter++;
    if (counter > ALLOWED_CONNECT_CYCLES) {
      ESP.deepSleep(SLEEP_TIME_SECONDS * 1000000);
    }
  }
 
  WiFiClient client;

  const int httpPort = 80;
  if (client.connect(host, httpPort)) {
    digitalWrite(0, HIGH);

    float temperature;
    counter = 0;
    do {
      DS18B20.requestTemperatures();
      temperature = DS18B20.getTempCByIndex(0);
      counter++;
      if (counter > ALLOWED_READ_CYCLES) {
        ESP.deepSleep(SLEEP_TIME_SECONDS * 1000000);
      }
    } while (temperature == 85.0 || temperature == (-127.0));

    client.print(String("GET /update?api_key=" + apiKey + "&field2=" + String(temperature)) + " HTTP/1.1\r\n" +
               "Host: " + host + "\r\n" + 
               "Connection: close\r\n\r\n");
    
  }

  delay(2000);
  
  ESP.deepSleep(SLEEP_TIME_SECONDS * 1000000);
}

void loop() {
}