Error de DNS ESP32

[SCSELECTRONICS]

Hello, for projects that require constantly connecting to fire, based on my perspective, I recommend setting a static configuration of IP, subnet, and DNS.

This is good because my project consists of constantly being on fire base to upload and read data, using the examples I modified so that they work in the long term but I was warned of a DNS error in a certain time apx between 10 minutes and 60 minutes, which I did was loading a static configuration.

debug:
[674304][E][NetworkManager.cpp:130] hostByName(): DNS Failed for 'xxxxxxx-default-rtdb.firebaseio.com' with error '-54'
[679319][I][ssl_client.cpp:129] start_ssl_client(): select returned due to timeout 5000 ms for fd 48
[679329][I][NetworkClientSecure.cpp:153] connect(): Actual TLS start postponed.
[679336][E][NetworkClientSecure.cpp:159] connect(): start_ssl_client: connect failed: -1
[679344][D][HTTPClient.cpp:1083] connect(): failed connect to xxxxxxx-default-rtdb.firebaseio.com:443
[679353][W][HTTPClient.cpp:1399] returnError(): error(-1): connection refused
[679361][E][NetworkClient.cpp:315] setSocketOption(): fail on 0, errno: 9, "Bad file number"
Error en la solicitud HTTP: -1
[679369][E][NetworkClient.cpp:315] setSocketOption(): fail on 0, errno: 9, "Bad file number"
[679380][D][HTTPClient.cpp:379] disconnect(): tcp is closed

Add this to my code:

IPAddress local_IP(192, 168, 100, 184);  
IPAddress gateway(192, 168, 100, 1);     
IPAddress subnet(255, 255, 255, 0);   
IPAddress primaryDNS(8, 8, 8, 8);      
IPAddress secondaryDNS(8, 8, 4, 4); 

void setup()
{

  Serial.begin(115200);

    
 if(!WiFi.config(local_IP, gateway, subnet, primaryDNS, secondaryDNS)) {
   Serial.println("Error al configurar la IP estática");
  }


  WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
  
}

my complete example code:

#include <Arduino.h>
#include <WiFi.h>


#include <FirebaseClient.h>

#define WIFI_SSID "WIFI_AP"
#define WIFI_PASSWORD "WIFI_PASSWORD"

// The API key can be obtained from Firebase console > Project Overview > Project settings.
#define API_KEY "Web_API_KEY"

// User Email and password that already registerd or added in your project.
#define USER_EMAIL "USER_EMAIL"
#define USER_PASSWORD "USER_PASSWORD"
#define DATABASE_URL "URL"

void authHandler();

void printResult(AsyncResult &aResult);

void printError(int code, const String &msg);

DefaultNetwork network; // initilize with boolean parameter to enable/disable network reconnection

UserAuth user_auth(API_KEY, USER_EMAIL, USER_PASSWORD);

FirebaseApp app;

#include <WiFiClientSecure.h>
WiFiClientSecure ssl_client;

using AsyncClient = AsyncClientClass;

AsyncClient aClient(ssl_client, getNetwork(network));

RealtimeDatabase Database;

AsyncResult aResult_no_callback;

IPAddress local_IP(192, 168, 100, 184);  
IPAddress gateway(192, 168, 100, 1);     
IPAddress subnet(255, 255, 255, 0);    
IPAddress primaryDNS(8, 8, 8, 8);      
IPAddress secondaryDNS(8, 8, 4, 4); 

void setup()
{

  Serial.begin(115200);

    
 if(!WiFi.config(local_IP, gateway, subnet, primaryDNS, secondaryDNS)) {
   Serial.println("Error al configurar la IP estática");
  }


  WiFi.begin(WIFI_SSID, WIFI_PASSWORD);

  Serial.print("Connecting to Wi-Fi");
  while (WiFi.status() != WL_CONNECTED){
    Serial.print(".");
    delay(300);
  }

  Serial.println();
  Serial.print("Connected with IP: ");
  Serial.println(WiFi.localIP());
  Serial.println();

  Firebase.printf("Firebase Client v%s\n", FIREBASE_CLIENT_VERSION);

  Serial.println("Initializing app...");

  ssl_client.setInsecure();

  initializeApp(aClient, app, getAuth(user_auth), aResult_no_callback);

  authHandler();

  // Binding the FirebaseApp for authentication handler.
  // To unbind, use Database.resetApp();
  app.getApp<RealtimeDatabase>(Database);

  Database.url(DATABASE_URL);

  // In case setting the external async result to the sync task (optional)
  // To unset, use unsetAsyncResult().
  aClient.setAsyncResult(aResult_no_callback);

  SetFB();

}

void loop(){
  GetFB();

  authHandler();
  Database.loop();

 delay(1000);

}

void authHandler(){
  // Blocking authentication handler with timeout
  unsigned long ms = millis();
  while (app.isInitialized() && !app.ready() && millis() - ms < 120 * 1000){
    // The JWT token processor required for ServiceAuth and CustomAuth authentications.
    // JWT is a static object of JWTClass and it's not thread safe.
    // In multi-threaded operations (multi-FirebaseApp), you have to define JWTClass for each FirebaseApp,
    // and set it to the FirebaseApp via FirebaseApp::setJWTProcessor(<JWTClass>), before calling initializeApp.
    JWT.loop(app.getAuth());
    printResult(aResult_no_callback);
  }
}
void printResult(AsyncResult &aResult){
 if(aResult.isEvent()){
   Firebase.printf("Event task: %s, msg: %s, code: %d\n", aResult.uid().c_str(), aResult.appEvent().message().c_str(), aResult.appEvent().code());
  }

 if(aResult.isDebug()){
   Firebase.printf("Debug task: %s, msg: %s\n", aResult.uid().c_str(), aResult.debug().c_str());
  }

 if(aResult.isError()){
   Firebase.printf("Error task: %s, msg: %s, code: %d\n", aResult.uid().c_str(), aResult.error().message().c_str(), aResult.error().code());
  }
}
void printError(int code, const String &msg){
  Firebase.printf("Error, msg: %s, code: %d\n", msg.c_str(), code);
}
void SetFB(){
  Serial.print("Set int... ");
  bool status = Database.set<int>(aClient, "/test/int", 12345);
 if (status)
    Serial.println("ok");
 else
   printError(aClient.lastError().code(), aClient.lastError().message());

  // Set bool
  Serial.print("Set bool... ");
  status = Database.set<bool>(aClient, "/test/bool", true);
 if (status)
   Serial.println("ok");
 else
   printError(aClient.lastError().code(), aClient.lastError().message());

 // Set string
  Serial.print("Set String... ");
  status = Database.set<String>(aClient, "/test/string", "hello");
 if (status)
   Serial.println("ok");
 else
   printError(aClient.lastError().code(), aClient.lastError().message());

 // Set float
  Serial.print("Set float... ");
  status = Database.set<number_t>(aClient, "/test/float", number_t(123.456, 2));
 if (status)
    Serial.println("ok");
 else
    printError(aClient.lastError().code(), aClient.lastError().message());

 // Set double

  Serial.print("Set double... ");
  status = Database.set<number_t>(aClient, "/test/double", number_t(1234.56789, 4));
 if (status)
    Serial.println("ok");
 else
   printError(aClient.lastError().code(), aClient.lastError().message());

}
void GetFB(){
  Serial.print("Get int... ");
  int v1 = Database.get<int>(aClient, "/test/int");
 if (aClient.lastError().code() == 0)
    Serial.println(v1);
  else
    printError(aClient.lastError().code(), aClient.lastError().message());

  Serial.print("Get bool... ");
  bool v2 = Database.get<bool>(aClient, "/test/bool");
 if (aClient.lastError().code() == 0)
   Serial.println(v2);
  else
   printError(aClient.lastError().code(), aClient.lastError().message());

  Serial.print("Get string... ");
  String v3 = Database.get<String>(aClient, "/test/string");
 if(aClient.lastError().code() == 0)
   Serial.println(v3);
  else
    printError(aClient.lastError().code(), aClient.lastError().message());

  Serial.print("Get float... ");
  float v4 = Database.get<float>(aClient, "/test/float");
 if(aClient.lastError().code() == 0)
   Serial.println(v4);
  else
   printError(aClient.lastError().code(), aClient.lastError().message());

  Serial.print("Get double... ");
  double v5 = Database.get<double>(aClient, "/test/double");
 if (aClient.lastError().code() == 0)
   Serial.println(v5);
 else
  printError(aClient.lastError().code(), aClient.lastError().message());
}

[mobizt]

The issue is not related to the server and network.

The TCP session was kept alive to avoid SSL/TLS handshake every time to send new HTTP request.

In your case the server session was timed out and it closes the connection. WiFiClientSecure (NetworkClientSecure) and WiFiClient (NetworkClient) are unable to detect this, the WiFiClientSecure::connected() always returns true.

This session timed out issue also posted in https://github.com/espressif/arduino-esp32, see issue #9924.

You have to manually call WiFiClientSecure::stop() when you send the new HTTP request after 2-3 minutes from the last request.

[mobizt]

Instead of manually stop the SSL Client, you can update the library to v1.2.16 which will limit the session timeout to avoid this WiFiClientSecure time out issue.