ESP-32 panic when trying to connect to the old socket about arduinowebsockets HOT 9 CLOSED

Hi Alexander,
First of all, I really appreciate the helpful attitude, thanks!

That's really interesting... I wonder if it is because wscat returns some weird answer in that case or if its a problem with the esp32 or library impl itself.

I will look into it. Thank you for the detailed issue.
Gil.

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So I ran few tests:

• The crash seems to be in esp32's function WiFiClient.read() (without any params, which should read one byte).
• The same scenario with another server impl does not crash the esp

I will keep you updated if I have any more information. Currently I'm not convinced that it's a library problem.

Gil 😃

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Interesting, I'll use your code tomorrow to try a few stuffs. I wonder if using .read() will crash (because this is what's crashing in the library). Also it's interesting that connected returns true after reset (if I understand correctly).

Thanks for the details, I'll let you know tomorrow if I learnt anything new.

Gil :)

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Closed :)

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Interesting, so you were able to reproduce the behaviour? I also don't think that it's a library problem actually but maybe some workaround could be implemented. I'm very curious to know what the difference is on TCP level in the different scenarios. Could maybe be investigated with Wireshark somehow.

With more info maybe it should be reported to Espressif?

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Hmm, just thought of something. We should try the same thing using only wifi-client and regular netcat. I will do so when I get back if you don't get to it before me.

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OK, interesting. I could not reproduce the crash using only WiFiClient and netcat.

Both reading and writing just fails silently when the arduino is connected to the "dead" socket. Also client.connected() returns true until I terminate the netcat program.

Here is the code I used:

#include <WiFi.h>

const char* ssid     = "";
const char* password = "";
const char* host = "";
int port = 1234;
WiFiClient client;
void setup()
{
  Serial.begin(115200);
  delay(10);
  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  if (!client.connect(host, port)) {
    Serial.println("connection failed");
    return;
  }
}

void loop()
{
  if (client.available()) {
    String line = client.readStringUntil('\r');
    Serial.print(line);
  } else if (!client.connected()) {
    Serial.println("Not connected");
  }
  client.print("hello");
  delay(1000);
}

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Hi,

So as you can see in the commit message I made a change that partially solves this issue. Now the client will not crash, it will just not connect to the server.

This is a good first step, but yet it's not possible to reconnect after such reset. It seems like it has more to do with Arduino internals and server impl and less with the library itself.

Let me know how the new code works for you, do you also not get a crash?

Gil.

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Works much better for me! I'm super happy with the board not crashing and ending up in my reconnect loop. Then if wscat tries to send something it detects that the client has disconnected and somehow starts to listen again and then the board can connect.

Great work!

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