ESP32 Fails to Reconnect to Wi-Fi Automatically

ESP32 Fails to Reconnect to Wi-Fi Automatically #

The ESP32 connects to Wi-Fi on boot, works as expected, but then disconnects and never reconnects unless you manually reset it. This is a common pitfall in many ESP32-based projects where reconnect logic isn’t properly implemented or deep sleep behavior isn’t handled correctly.

This guide explains why the ESP32 doesn’t reconnect automatically after a disconnection and how to reliably restore Wi-Fi connections in all scenarios.

What Causes Reconnect Failures? #

🔁 No Reconnect Logic in Code #

Unlike many mobile devices, the ESP32 does not automatically reconnect to Wi-Fi after losing signal or after the router reboots — unless your code tells it to. If you only call WiFi.begin(ssid, password) once in setup(), the device won’t attempt reconnection after a dropout.

🌙 Coming Back from Deep Sleep #

When the ESP32 wakes from deep sleep, all RAM (except RTC memory) is cleared. That includes any stored Wi-Fi connection state. Unless you re-run your connection logic on wake-up, the device will boot without any network access.

⚠️ Router Reboot Takes Time #

Many routers take 20–60 seconds to reboot. If the ESP32 tries to reconnect immediately and fails, and you don’t retry later, it will remain offline.

🧯 Static IP Without Retry Handling #

If you’re using a static IP with WiFi.config(), and don’t actively check for connection status, the ESP32 will think it’s connected (IP is set) — but it won’t be online if the Wi-Fi handshake didn’t complete. Reconnection must be triggered manually.

Detecting Reconnect Issues #

• Serial monitor shows:

WiFi disconnected. Reason: 200

  
  

      

but nothing follows.

• After a power blink or Wi-Fi outage, the ESP32 never reconnects unless reset.

• In deep sleep projects, the device wakes up and runs code, but network functions (MQTT, HTTP, etc.) fail silently.

How to Fix Reconnection Problems #

✅ Use Wi-Fi Event Handlers #

Add this in your setup() function to listen for disconnection events:

WiFi.onEvent([](WiFiEvent_t event){
if (event == SYSTEM_EVENT_STA_DISCONNECTED) {
  Serial.println("WiFi disconnected! Attempting reconnect...");
  WiFi.reconnect();
}
});

  
  

      

This ensures a reconnect is triggered automatically whenever the link drops.

✅ Periodically Check and Reconnect #

If you prefer a simpler method, poll WiFi.status() in loop():

if (WiFi.status() != WL_CONNECTED) {
  WiFi.begin(ssid, password);
}

  
  

      

Use a timer or interval to avoid hammering the connection.

✅ Handle Deep Sleep Properly #

On wake from deep sleep, re-initiate the Wi-Fi connection in setup():

WiFi.begin(ssid, password);

  
  

      

Optionally, store credentials in RTC memory or EEPROM and restore on wake-up. You can also delay actions (like MQTT publish) until Wi-Fi is confirmed:

while (WiFi.status() != WL_CONNECTED) {
  delay(500);
}

  
  

      

✅ Add Retry Delay or Watchdog Recovery #

If the router is still rebooting when the ESP32 tries to reconnect, it may fail too early. Use a retry loop or watchdog to keep checking for available networks before proceeding.

Conclusion #

The ESP32 doesn’t reconnect to Wi-Fi by default — especially after disconnections or deep sleep. But with a few lines of code, you can make it resilient and always online.

Checklist:

• Use WiFi.onEvent() to handle drops

• Re-run WiFi.begin() after wake-up or failure

• Don’t rely on static IP to mean you're connected

• Add logging to catch missed events

With proper reconnect handling, your ESP32-based device can operate reliably over hours, days, and beyond — even in dynamic Wi-Fi environments.