Exception in WiFiClient when WiFi is disconnected

[pakokol]

Basic Infos

Hardware

Hardware: ESP-WROOM-02
Core Version: 2.4.0

Description

WiFiClient causes exception 28 in connect function.

Settings in IDE

Module: Generic ESP8266 Module
Flash Size: 2M
CPU Frequency: 80Mhz
Flash Mode: DIO
Flash Frequency: 40Mhz
Upload Using: SERIAL
Reset Method: ck

Sketch

#include <ESP8266WiFi.h>
#include <Esp.h>

const char *ssid      = "MySSID";
const char *password  = "MyPass";

const char *serverIP  = "192.168.1.106";
const int  serverPort = 1883;

WiFiClient client;

void toggleLED()
{
  pinMode(5, OUTPUT);
  digitalWrite(5, HIGH);
  delay(250);
  digitalWrite(5, LOW);
  delay(250);
}

void setup() {
  // put your setup code here, to run once:
    Serial.begin(115200);
    WiFi.setOutputPower(20.5);
    WiFi.mode(WIFI_STA);
    WiFi.begin(ssid, password);
}

void loop() {
  if(WiFi.status() == WL_CONNECTED)
  {
    Serial.println("Connected to WiFi");
    if(!client.connect(serverIP, serverPort))
    {
      Serial.println("Can't connect client.");
    }
    else
    {
      Serial.println("Client connected."); 
    }
  }
  else
  {
     Serial.println("Not connected to WiFi");
  }
  
  toggleLED();
}

Debug Messages

Exception (28):
epc1=0x40202af1 epc2=0x00000000 epc3=0x00000000 excvaddr=0x000000bb depc=0x00000000

ctx: cont 
sp: 3ffefcd0 end: 3ffeff00 offset: 01a0
>>>stack>>>
3ffefe70:  3ffeec58 00000000 3fff112c 40202aea 
3ffefe80:  6a01a8c0 00000010 3ffe8880 3ffeeecc  
3ffefe90:  3fffdad0 00000011 3ffeeea0 3ffeeecc  
3ffefea0:  3fffdad0 0000075b 3ffeec58 402026a8 
3ffefeb0:  3ffe8bf0 6a01a8c0 3ffe8bf0 6a01a8c0  
3ffefec0:  3ffe88c8 40202460 3ffeeea0 40203198 
3ffefed0:  00000000 00000000 3ffeeea0 40202132
3ffefee0:  3fffdad0 00000000 3ffeeec4 40203404
3ffefef0:  feefeffe feefeffe 3ffeeee0 40100710 
<<<stack<<<<
 ets Jan  8 2013,rst cause:1, boot mode:(3,6)

load 0x4010f000, len 1384, room 16 
tail 8
chksum 0x2d
csum 0x2d

I'm trying to connect to a MQTT server. It connects to the server and works as expected. But when I turn of my router and the connection is lost it crashes with exception 28. Am I using something wrong or is this a bug?

[igrr]

I can confirm this. Doesn't happen with LwIP v1.4 selected.

Log output with 1.4 when WiFi disconnects:

:ref 1
Client connected.
state: 5 -> 0 (0)
rm 0
:er -8 0x00000000
del if0
usl
mode : null
wifi evt: 1
STA disconnect: 8
:ur 1
:del

With 2.0, this results either in an exception or a hardware WDT (still wondering how that happens):

:ref 1
Client connected.
state: 5 -> 0 (0)
rm 0
del if0
usl
mode : null
wifi evt: 1
STA disconnect: 8
:ur 1
:close

 ets Jan  8 2013,rst cause:4, boot mode:(3,6)

wdt reset

Seems that if TCP disconnect is triggered after WiFi goes down, this results in an invalid memory access somewhere.

With LwIP 1.4, TCP PCB receives error callback (log with :er -8), and closes the connection, while with LwIP 2, this error callback is not sent. When WiFiClient.connect is called again, old connection is closed (tcp_close), but the network interface is already dead. Why this triggers a hardware WDT is something i don't entirely understand though.

[d-a-v]

The "del if0" is treated differently in lwip2. I'll check asap.

…

-- on mobile

On January 4, 2018 2:26:20 PM Ivan Grokhotkov ***@***.***> wrote: I can confirm this. Doesn't happen with LwIP v1.4 selected. Log output with 1.4 when WiFi disconnects: ``` :ref 1 Client connected. state: 5 -> 0 (0) rm 0 :er -8 0x00000000 del if0 usl mode : null wifi evt: 1 STA disconnect: 8 :ur 1 :del ``` With 2.0, this results either in an exception or a hardware WDT (still wondering how that happens): ``` :ref 1 Client connected. state: 5 -> 0 (0) rm 0 del if0 usl mode : null wifi evt: 1 STA disconnect: 8 :ur 1 :close ets Jan 8 2013,rst cause:4, boot mode:(3,6) wdt reset ``` Seems that if TCP disconnect is triggered after WiFi goes down, this results in an invalid memory access somewhere. -- You are receiving this because you are subscribed to this thread. Reply to this email directly or view it on GitHub: #4078 (comment)

[jp112sdl]

Thanks for reproducing!

That's the same behavior I described here a few days ago.

[pakokol]

Thank you for your explanation! Where can I change to LwIP v1.4 if it is possible without changing core version?

[jp112sdl]

@pakokol In Arduino IDE you can change it in the Tools menu

[pakokol]

@jp112sdl Thank you!

[d-a-v]

about lwip2:
I think I have fixed the wdt problem, but i still need to understand what is triggering wifi_station_get_connect_status() result. It does not go back to STATION_GOT_IP even though dhcp is re-triggered. I will dig deeper.