How to reconnect esp32 to wifi after getting disconnected temporarily using wifimanager library and not halting

Question

Can someone please suggest how to reconnect automatically to the last known wifi network (through wifi manager library) after it gets disconnected for a while and without blocking forever till a network is connected?

The below code will work but needs restart every time a network is lost or no network was found during initialization. But I cannot block it till network is connected because my program is supposed to run both in offline and online mode, ie can control pins even there is no internet, and in every loop it will try to connect to network. If network is available then control the pins using Blynk.

#include <WiFi.h>

#include <WiFiClient.h>

#include <WebServer.h> //copiedota
#include <ESPmDNS.h> //copiedota
#include <Update.h> //copiedota


#include <WiFiManager.h>   
#include <ArduinoJson.h>          // https://github.com/bblanchon/ArduinoJson


#include <BlynkSimpleEsp32.h>
BlynkTimer timer;

#define DEBUG_SW 1

// By default the mode is with_internet
int MODE = 0;
bool connected_once = false;

char auth[] = "***";

// Your WiFi credentials.
const char* host = "shariqESP"; //copiedota
// Set password to "" for open networks.

char ssid[] = "rm7pro";

//char ssid[] = "";

char pass[] = <"*****">;

void setup()
{
  // put your setup code here, to run once:
  Serial.begin(9600);
  
  //WiFiManager
  //Local intialization. Once its business is done, there is no need to keep it around
  WiFiManager wm;

  wm.setConfigPortalTimeout(40);
  
   //wm.setDebugOutput(true);
  
Serial.printf("SSID0: %s\n", wm.getWiFiSSID().c_str());
String saved_ssid_old =wm.getWiFiSSID().c_str();

  if(!wm.autoConnect("AutoConnectAP")) {
    Serial.println("failed to connect and hit timeout");
    delay(3000);
    //reset and try again, or maybe put it to deep sleep
    //ESP.restart();
    //delay(5000);
  } 
   Serial.printf("SSID1: %s\n", WiFi.SSID().c_str());
   Serial.println("SSID00: " + (String)wm.getWiFiSSID());
   Serial.println( wm.getWiFiIsSaved() );


if(WiFi.SSID().c_str() == ""){

int str_len = saved_ssid_old.length() + 1; 
char char_array[str_len];
// Copy it over 
saved_ssid_old.toCharArray(char_array, str_len);
Serial.println( ssid);

strcpy(ssid , char_array);

}
  
if(WiFi.SSID().c_str() != ""){
    Serial.println("not blank");

  String saved_ssid =WiFi.SSID().c_str();
  String saved_ssid_old =wm.getWiFiSSID().c_str();
  Serial.println(saved_ssid);
  Serial.println( saved_ssid_old );

    //if( !saved_ssid_old.equals(saved_ssid)  ){
      // Length (with one extra character for the null terminator)
      int str_len = saved_ssid.length() + 1; 
  // Prepare the character array (the buffer)
  char char_array[str_len];
   
  // Copy it over 
  saved_ssid.toCharArray(char_array, str_len);
  Serial.println( ssid);
  Serial.println( "different ssid");
  

  memset( ssid,0, sizeof(ssid)) ;
  //char ssid[str_len];
  strcpy(ssid , char_array);


char ssid2[] ="rm7pro";
if ( strcmp(ssid2, ssid) == 0 ) {
  Serial.println( "same ssid"); 

}
else if ( strcmp(ssid2, ssid)  > 0 ){
  Serial.println( "rm7pro is great same ssid"); 

}
else{
   Serial.println( "rm7pro is less same ssid"); 

  }
       
   // }
        
}
Serial.print("Now printing SSID:");
  Serial.println( ssid);

wm.disconnect();
delay(1000);  

   WiFi.begin(ssid, pass);
    Serial.print("main begin ssid:");
    Serial.println(ssid);
    int ct= 0;
      Serial.print("before while ssid:");
    Serial.println(ssid);
    
    while(WiFi.status() != WL_CONNECTED ){
      delay(1000);
      ct=ct+1000;
      if(ct>5000){
        Serial.println("not able to connect to wifi");        
        break;
        }
      }

    Serial.print("after while bfore if ssid:");
    Serial.println(ssid);
    
   if (WiFi.status() == WL_CONNECTED)
  {
     Serial.println( "connected once");
   connected_once = true;
  }
  Serial.print("before while after if ssid:");
    Serial.println(ssid);
  
  //setOTA(); //custom

   Serial.print("End ssid:");
    Serial.println(ssid);
}


void loop()
{
  Serial.println("Loop started");
  Serial.print("Wifi status: ");
  Serial.println(WiFi.status());
   Serial.print("Start ssid:");
    Serial.println(ssid);
  
  if (WiFi.status() != WL_CONNECTED)
  {
    Serial.print(ssid);
    Serial.println(WiFi.SSID().c_str() );
    if (DEBUG_SW) Serial.println("Not Connected");
    
   /* if( connected_once == true){
      Serial.println("Reconnecting");
        WiFi.disconnect();
        delay(1100); //custom

        WiFi.begin(ssid, pass);
    //WiFi.reconnect();
    }
    else{*/
      Serial.println("Re-attempting to connect");
      //WiFi.reconnect();
       WiFi.disconnect();
        delay(500); //custom
        WiFi.begin(ssid, pass);
         delay(1200); //custom
    //  }
  }
  else
  {
    if (DEBUG_SW) Serial.println(" Connected");
    //Blynk.run();
  }
 delay(400); //custom

}

If you observe the image now, you will notice that the esp wont connect to wifi even though providing the same ssid, it will still not connect.

Which is very strange as per my understanding.

Please suggest I am badly struck here.

Regards, Shariq

Answer 1

I realised the issue was with this lines ork is available then control the pins using Blynk.

    if (WiFi.status() == WL_CONNECTED)
   {
      Serial.println( "connected once");
    connected_once = true;
   }

This was somehow causing memory issue.

I also added while loop inside loop function with a 10 sec timeout counter to reconnect.

       while(WiFi.status() != WL_CONNECTED)
      {
    delay(1000);
         ct=ct +1000;
    if(ct >11000){
    break;
    }
    
      }