MQTT deep sleep

#include <WiFi.h>
#include <PubSubClient.h>

WiFiClient espClient;
PubSubClient client(espClient);

// Create an object of the class Bsec
//Bsec iaqSensor;

#define BUILTIN_LED 4

#define SSID "xxxxxx"
#define PWD "xxxxxx"

#define mqtt_user "user"
#define mqtt_pwd "password"


// env variable
String temperature;
String humidity;
String pressure;
String CO2;
String gasResistance;

bool can_sleep = false;

void WiFiStationGotIP(WiFiEvent_t event, WiFiEventInfo_t info){
  Serial.print("WiFi connected. IP: ");
  Serial.println(WiFi.localIP());

  // Connect to MQTT broker (with timeout)
  bool connected = connectToBroker();
  unsigned long timeout = millis();
  while ( !connected ) {
    delay(1000);
    connected = connectToBroker();
    if(millis() - timeout > 5000){
      connected = false;
      break;
    }
  }

  // Publish data
  if(connected) {
    publishData();
    // Once connected at least one time, eSP32 can sleep
    can_sleep = true;
  }
}


bool connectToBroker(){
  Serial.print("Attempting MQTT connection...");
  // Create a random client ID
  String clientId = "ESP8266Client-";
  clientId += String(random(0xffff), HEX);

  // Attempt to connect
  if (client.connect(clientId.c_str(), mqtt_user, mqtt_pwd)) {
    Serial.println("connected");
    return true;
  }
  else {
    // Error on connection (host unreachable)
    Serial.print("failed, rc=");
    Serial.print(client.state());
    delay(100);
  }
  return false;
}


void publishData(){

  #define MSG_BUFFER_SIZE  (50)
  char msg[MSG_BUFFER_SIZE];
  static int value = 0;
  snprintf (msg, MSG_BUFFER_SIZE, "hello world #%ld", ++value);
  Serial.print("Publish message: ");
  Serial.println(msg);

  temperature = 25.6 + random(5);
  humidity = 45 + random(10);
  Serial.println("Umidità:"+(String)temperature);
  Serial.println("Temperatura:"+(String)humidity);

  client.publish("esp32/humidity", humidity.c_str());
  client.publish("esp32/temperature", temperature.c_str());

  //wait a little before sleep, so data can be sent to broker
  delay(200);
}


void setup() {
  Serial.begin(115200);

  Serial.print("Connecting to ");
  Serial.println(SSID);

  WiFi.onEvent(WiFiStationGotIP, SYSTEM_EVENT_STA_GOT_IP);
  WiFi.begin(SSID, PWD);

  // Test on local LAN mosquitto broker
  IPAddress ip;
  ip.fromString("192.168.2.81");
  client.setServer(ip, 1883);
}



void loop() {

  if(can_sleep){
    // ESP32 wakes up every 30 seconds
    esp_sleep_enable_timer_wakeup(10000000);
    Serial.println("Going to deep-sleep now");
    Serial.flush();

    esp_deep_sleep_start();
    while (WiFi.status() != WL_CONNECTED) {;}

  }

}