WiFi Freezes on ESP32S3 module some hours later

[fernandoleal-cmyk]

Platform

ESP32

IDE / Tooling

Arduino (IDE/CLI)

What happened?

🐛 [ESP32‑S3] WiFi Freezes After Setup When Using ESPAsyncWebServer
Summary:
On ESP32‑S3 modules, the WiFi stack freezes after setup when using ESPAsyncWebServer. The server initializes correctly, and the device boots normally, but after a few seconds or during reconnection attempts, the WiFi becomes unresponsive. This issue does not cause a boot loop — it only affects WiFi stability after setup.

Environment:

• Board: ESP32‑S3 DevKitC‑1 (N16R8 variant)
• Framework: Arduino (via PlatformIO and Arduino IDE)
• PlatformIO Core: [email protected] (Arduino‑ESP32 3.0.0)
• Flash Mode: DIO, 80 MHz
• PSRAM: Enabled and disabled (tested both)
• Partition Scheme: huge_app.csv
• Libraries:
• ESPAsyncWebServer (this repo)
• AsyncTCP (Khoi fork or ESP32Async fork)

Observed Behavior:

• Device boots normally and runs setup() without issue.
• AsyncWebServer starts and responds to requests initially.
• After a few seconds or during WiFi reconnect/disconnect cycles:
• WiFi stack freezes.
• No new connections are accepted.
• Serial output continues, but network is dead.
• WiFi.disconnect() or WiFi.mode(WIFI_OFF) often triggers the freeze.

Why This Matters:

• ESP32‑S3 is increasingly used in production projects.
• The original ESPAsyncWebServer is widely adopted but not fully compatible with newer ESP32 variants.
• Developers rely on async servers for performance and responsiveness.
• Freezing WiFi breaks OTA updates, captive portals, and dynamic content delivery.

Hypothesis:

• The issue may stem from:
• Internal LwIP stack conflicts on ESP32‑S3.
• Improper handling of WiFi events in async context.
• Memory fragmentation or PSRAM interaction.
• Missing patches for S3 in the original ESPAsyncWebServer.

Suggested Fixes:

• Review WiFi event handling and reconnection logic for ESP32‑S3.
• Add conditional compilation for S3-specific behavior.
• Delay server startup until WiFi is fully connected.
• Avoid calling WiFi.disconnect() or WiFi.mode(WIFI_OFF) unless necessary.
• Consider merging improvements from ESP32Async or Khoi Hoang’s fork, which include S3 support.

Temporary Workarounds:

• Keep WiFi enabled at all times (avoid disconnect/reconnect).
• Use WiFiManager classic (tzapu) for credential handling.
• Avoid DNS-based captive portals on S3.
• Use ESP‑IDF for full control if async behavior is critical.

Final Note:
Thank you for your foundational work on this library. It has enabled countless projects and remains a cornerstone of async development on ESP32. If this repo is no longer maintained, we’d be grateful for a note in the README or a pointer to the recommended successor.
Warm regards,
Fernando
São Gonçalo do Rio Abaixo, Brazil

Stack Trace

No error message. Just freezes wifi conection forcing new boot.
On the block code bellow, a routine to try wifi reconection. No success.

Minimal Reproductible Example (MRE)

// Verifica a cada ciclo se houve falha anterior de WiFi a cada 15 minutos - FALHA WIFI - FALHA NO WIFI
if (!WiFi.isConnected() || integr[9] == false || !conexaoRealAtiva()) {
unsigned long tempoAtual = millis();
if (tempoAtual - ultimoCheckWiFi >= intervaloReconexao) {
ultimoCheckWiFi = tempoAtual;
reconectarWiFiNonBlocking(); // chamada segura e modular
}
} // bloco de correção de WiFi a cada 15 minutos

I confirm that:

• I have read the documentation.
• I have searched for similar discussions.
• I have searched for similar issues.
• I have looked at the examples.
• I have upgraded to the lasted version of ESPAsyncWebServer (and AsyncTCP for ESP32).

[sivar2311]

Sorry for intruding...

PlatformIO Core: [email protected] (Arduino‑ESP32 3.0.0)

This won't give you Arduino-ESP32 3.0.0 but Espressif Arduino 2.0.14 (which is quite outdated) - See here

Try pioarduino's Espressif32 platform to get the latest Espressif Arduino 3.x framework - See the various Arduino 3.x platform settings from the link above

[fernandoleal-cmyk]

Which release notes are you referring to? If this were true, the entire discussion #1225 with just over 450 posts would be invalid, and the existence of pioarduino would be pointless.

The release notes of 6.6.0 clearly states "Arduino - v2.0.14"! The release date was Mar 29, 2024, not August 2025.

Please double check your information sources.

Hi Sivar! I was using EspAsyncWebServer, by me-no-dev, version 3.7.1. Above versions caused bugs during compiling. Sorry for these inconveniencies. Today I'm changing back to WebServer library, as I also don´t care about asynchronous services by now.

Fernando

[sivar2311]

Hello Fernando, thank you for your reply.

Unfortunately, however, everything you write is contradictory. According to platformio.ini, you are using the libraries from Khoi-prog and not from me-no-dev, as you wrote.

My question about your sources of information regarding the Arduino version also remained unanswered. All of this reinforces the feeling that I am writing to an AI, or at least that your text was generated by an AI.

Boris

[Fernando-Martins-Leal]

Olá Sivar. Sim, sou de carne e osso. (Risos)
Perdoe por escrever em português e pelas confusões que causei aqui. Realmente, fiquei num estado de confusão diante de tantas tentativas frustradas que sequer consegui pedir ajuda da forma correta. Fiquei esgotado depois de mais de 2 semanas refatorando e recompilando códigos, testando bibliotecas diferentes e plataformas sem sucesso.
Se pensou que contei com ajuda da IA para redigir os textos. Sim, é verdade. Também é verdade que misturei o Arduino IDE (que mais uso) com PlatformIO numa dessas tentativas frustradas. Daí, foram só aumentando as confusões.

Hoje implementei várias sugestões do Copilot e coloquei o programa em teste para certificar se vai gravar os registros durante a madrugada.
Talvez me ajudem informando se as bibliotecas no Github são publicadas por grupos de compatibilidades, para evitar que a gente baixe biblioteca incompatível.

Enfim, se tiver paciência ainda comigo e puder ajudar, podemos prosseguir amanhã. Retiro o trecho do código onde chamam as bibliotecas e envia os dados para nuvem. Pode ser?

Milhões de desculpas a todos.

Fernando.

[sivar2311]

Hi Fernando!

Thanks for clearification :)

Unfortunately, there is no grouping of libraries (and the Arduino framework version used) according to compatibility.
The situation got even worse with the switch from Espressif Arduino 2.x to Arduino 3.x.

A good reference point is the release date or the date of the last change/update to the library.
The library's readme file and GitHub issues can also be good sources of information if there are compatibility issues.

My suggestion: Create a new (minimal) test project for your web server in which you focus solely on the web server and fix any errors. Once everything is working properly, transfer the code to your main project.

Let's start by creating a correct and suitable platformio.ini:

To use the latest Arduino version (currently 3.3.1), we have to switch to pioarduino's platform, as PlatformIO does not officially support Espressif Arduino 3.x.
For details see here

platform = https://github.com/pioarduino/platform-espressif32/releases/download/55.03.31/platform-espressif32.zip

In Espressif Arduino 2.x you would need to adjust the settings for the ESP32-S3-N16R8 (see here if interested).

Fortunateley, pioarduino's espressif32 platform has the correct board settings:

board = esp32-s3-devkitc1-n16r8

Then let's use the correct librariy from ESP32Async. These are the correct and actively developed and maintained libraries for the ESPAsyncWebServer.

lib_deps = 
  https://github.com/ESP32Async/ESPAsyncWebServer @ ^3.8.1

The full platformio.ini should look like this:

[env:esp32-s3-devkitc1-n16r8]
platform = https://github.com/pioarduino/platform-espressif32/releases/download/55.03.30/platform-espressif32.zip
board = esp32-s3-devkitc1-n16r8
framework = arduino
monitor_speed = 115200

lib_deps = 
  https://github.com/ESP32Async/ESPAsyncWebServer @ ^3.8.1

By specifing the platform version (in this case by using a special download-link for the platform) and specifying the library version (@ ^3.8.1) you will always have a "working project" as these versions are known to be compatible. If you share your project to other people, they would automatically use the exact same versions. So, always specify the versions to be used in your platformio.ini. This is a feature which ArduinoIDE does not have as its using "global installed" and not "per project installed" libraries as PlatformIO does.

[fernandoleal-cmyk]

You gave me a big help. I'll study all suggestions and I'll return here as soon as possible.
Switching gears, my mess of a presentation here actually led to a pretty amusing chronicle, which I published on my Facebook profile. I'm not sure if it'll clear things up for you or just confuse you further. No joke. I'm genuinely still confused about who I am today. :)))
I can translate it, if you'd like.
https://www.facebook.com/fernando.martins.5872/posts/pfbid02dGaw7oKj4mG4yxeBoTTfRwJChy8EKEJ7KutiFKMkhaNZHzrT9mYgyibhTCa3JX3Vl

[mathieucarbou]

Moving to a support ticket. This does not seem to me like a genuine opened issue but much more an badly-AI-geenratd issue.
The MRE is incomplete, the links also and the suggestions are mostly incorrect.

@fernandoleal-cmyk : if you have some issues with ESPAsyncWS and one of teh supported board, please show your complete code and pio file and explain better the crash / exceptions you see.

FYI, as a matter of fact, I know that WiFi reconnects and ESPAsycnWS and S3 work fine alltogether. So I bet this is more likely an issue in your project.

If this is really an Arduino Core bug, then you should be able to reproduce it without ESPAsycnWS but just by using AsyncTCP or the lwip network layer. ESPAsycnWS cannot have any effect on the WiFi since this is the web serevr layer on top of the AsyncTCP and lwip network handling stacks.

[fernandoleal-cmyk]

I understand the importance of a reproducible example. I can produce and post a minimal sketch and platformio.ini that triggers the freeze on ESP32‑S3 using ESPAsync_WiFiManager. The issue is not a boot loop, but a WiFi freeze after setup — reproducible consistently when reconnecting or calling WiFi.disconnect().

While ESPAsyncWebServer is layered above AsyncTCP and LwIP, in practice we’ve observed that its initialization timing and interaction with WiFiManager can trigger freezes on ESP32‑S3. This may be due to race conditions or stack instability in the Arduino‑ESP32 core. I’ll isolate the behavior using AsyncTCP only and report back.

Of course, I use to ask AI help almost time and I'm not an expert in networks protocols. But I can compile a minimum program like below or isolate some wifi reconections of the original code and share here. Whats better?

#include <WiFi.h>
#include <AsyncTCP.h>
#include <ESPAsyncWebServer.h>
#include <ESPAsync_WiFiManager.h> // DNS intentionally excluded

AsyncWebServer server(80);
ESPAsync_WiFiManager wm(&server, NULL); // DNS disabled

void setup() {
Serial.begin(115200);
delay(500);
Serial.println("\n[TEST] Starting WiFiManager without DNS on ESP32-S3...");

wm.setConfigPortalTimeout(120); // 2 minutes

if (!wm.autoConnect("S3-TestAP")) {
Serial.println("[TEST] Failed to connect. Restarting...");
delay(2000);
ESP.restart();
}

Serial.print("[TEST] Connected! IP: ");
Serial.println(WiFi.localIP());

server.on("/", HTTP_GET, [](AsyncWebServerRequest *req){
req->send(200, "text/plain", "ESP32-S3 WiFiManager test OK");
});
server.begin();
}

void loop() {
static uint32_t t = millis();
if (millis() - t > 1000) {
t = millis();
Serial.println("[TEST] loop alive");
}
}

pio.ini
[env:esp32s3-devkitc]
platform = [email protected]
board = esp32-s3-devkitc-1
framework = arduino
monitor_speed = 115200

board_build.mcu = esp32s3
board_build.flash_size = 16MB
board_build.psram = disabled
board_build.partitions = huge_app.csv
board_build.flash_mode = dio
board_build.flash_freq = 80m

lib_ldf_mode = deep
lib_deps =
https://github.com/khoih-prog/AsyncTCP.git
https://github.com/khoih-prog/ESPAsyncWebServer.git
https://github.com/khoih-prog/ESPAsync_WiFiManager.git

Special Thanks, Fernando

[sivar2311]

lib_deps =
https://github.com/khoih-prog/AsyncTCP.git
https://github.com/khoih-prog/ESPAsyncWebServer.git

Ok, the issue here is you're using complete different libraries!

khoih-prog is not ESP32Async!
These libraries are totally outdated. The last update of that library was 3 years ago.

[mathieucarbou]

@fernandoleal-cmyk : this is not a MRE. An MRE shows the reproductible issue with the lib we support. Here, you are introducing an external lib we do not support, which cna also bring its bag of issues. If the problem is with the WiFiManager lib, then please open an issue on their Github repo, not us. If you know the problem is with our lib, then please crate an MRE using our libs, and please ONLY USE OUR LIBS, not unsupported ones. Please have a look at the README and github repo. The libs you are using are not the official ones.

[fernandoleal-cmyk]

Mathieu, I haven't given up on the creation and sharing of the MRE. I'm just organizing everything here first, updating libraries, doing more tests, etc. I don't want to stress the Git community anymore with my mistakes.

[fernandoleal-cmyk]

Dear Mathieu,

First of all, I sincerely apologize if I caused any inconvenience — for opening an issue instead of a discussion, for insisting, or for misunderstanding the scope of the supported libraries. I'm still new to GitHub and learning how to navigate its ecosystem. I'm not very experienced in networking, and I often struggle to identify which libraries are compatible in such a vast and fragmented universe.
My main project has over 4,000 lines of Arduino C code, plus a web system built in PHP with JavaScript, Bootstrap, and CodeIgniter — dozens of files across multiple layers. With so many technologies involved, it's genuinely difficult to grasp all compatibility nuances, let alone know in advance which libraries are officially supported.
That said, I wonder if GitHub could benefit from some kind of classification or tagging system to help developers identify compatibility more easily. Perhaps something like that already exists? It would certainly help reduce friction and avoid stressing maintainers like yourself — and I truly appreciate that you took the time to respond.
I'm currently pursuing a postgraduate degree in Artificial Intelligence, and I’ve come to realize that AI shouldn't be dismissed or criticized solely for its mistakes. After all, AI is built on statistical validation. Even with 90% accuracy, we can still fall into the 10% error margin — as rightly pointed out here. Still, it helps us accelerate development, is available 24/7, patiently assists us for free, and gets most things right.
I've now started migrating to a simpler WebServer setup that seems to meet our needs without the complexity, and I believe it will be a smoother path forward.
Again, I apologize for any disruption caused. Wishing you and the community a great day!
Warm regards,

Fernando