void setup() {
  Serial.begin(115200);
  Serial2.begin(115200);
  pinMode(AP_SWITCH, INPUT);
  pinMode(con_led, OUTPUT);
  pinMode(network_led, OUTPUT);
  digitalWrite(con_led, HIGH);
  digitalWrite(network_led, HIGH);
  attachInterrupt(digitalPinToInterrupt(AP_SWITCH), handleInterrupt, FALLING);
   wifiManager.autoConnect(AP_NAME,AP_PASSWORD);
  client.setTimeout(5);
   Serial.println("Connected");
}

void loop() {

  // Use WiFiClient class to create TCP connections
  if(ap_switch_flag == 1){
    wifiManager.resetSettings();
    wifiManager.autoConnect(AP_NAME,AP_PASSWORD);
    ap_switch_flag = 0;
  }
  if(!client.connected()){  
   if (!client.connect(server, port)) {
    Serial.print("dccqaec");
   }
    else {
      digitalWrite(con_led, LOW);
   }
  } else {
    send_serialdata_to_server();
    send_serverdata_to_serial();
  }
  if ( (!client.connected())) {
    slowBlink();
  }
  if ( (client.connected())) {
    fastBlink();
  }
  if (!client.connected()) {
    digitalWrite(con_led, HIGH); 
  }

}

Using this code i have connected the ESP withmy phones hotspot. It works fine. But when i turn off the mobile data, it is not able to detect the TCP disconnection. Also tried giving the timeout in setup.