ESP32 WiFiMulti: Connect to the Strongest Wi-Fi Network (from a list of networks)

Learn how to use WiFiMulti with the ESP32. It allows you to register multiple networks (SSID/password combinations). The ESP32 will connect to the Wi-Fi network with the strongest signal (RSSI). If the connection is lost, it will connect to the next network on the list.

Using WiFiMulti in your ESP32 IoT projects is useful if your board can have access to more than one Wi-Fi network. Implementing this feature in your projects is very simple and improves your projects significantly.

ESP32 with WiFiMulti

You can easily add WiFiMulti to your ESP32 projects with just a few lines of code. You can find an example in your Arduino IDE. With an ESP32 board select (Tools > Board), go to File > Examples > WiFi > WifiMulti.

Here are the essential steps to use WiFiMulti with the ESP32.

Include Libraries

First, you need to include both WiFi.h and WiFiMulti.h libraries.

#include <WiFi.h>
#include <WiFiMulti.h>

WiFiMulti Object

Then, you need to create a WiFiMulti object:

WiFiMulti wifiMulti;

Add List of Networks

Then, in the setup(), use the addAp() method on the wifiMulti object to add a network. The addAP() method accepts as arguments the network SSID and password. You should add at least one network.

wifiMulti.addAP("ssid_from_AP_1", "your_password_for_AP_1");
wifiMulti.addAP("ssid_from_AP_2", "your_password_for_AP_2");
wifiMulti.addAP("ssid_from_AP_3", "your_password_for_AP_3");

Connect to Wi-Fi

Finally, connect to Wi-Fi using the run() method. You can also print a message in case the Wi-Fi is disconnected.

if(wifiMulti.run() != WL_CONNECTED) {
  Serial.println("WiFi not connected!");
  delay(1000);
}

You can run this snippet on the loop() section and if the ESP32 gets disconnected from a Wi-Fi network, it will automatically try to connect to the next strongest network on the list.

ESP32 with WiFiMulti Example

For you to understand how WiFiMulti works with the ESP32, we created a simple example that does the following:

• scans for available wi-fi networks and prints their RSSI (so that you can check that the ESP32 is actually connecting to the strongest network on the list);
• connects to the strongest wi-fi network from a list of provided networks;
• in case it loses connection with the network, it will automatically connect to the next strongest network on the list.

To test this, you can copy the following code to your Arduino IDE. It is based on the WiFiScan and WiFiMulti examples provided in the Arduino core examples for the ESP32.

/*
 *  Based on the following examples:
 *  WiFi > WiFiMulti: https://github.com/espressif/arduino-esp32/blob/master/libraries/WiFi/examples/WiFiMulti/WiFiMulti.ino
 *  WiFi > WiFiScan: https://github.com/espressif/arduino-esp32/blob/master/libraries/WiFi/examples/WiFiScan/WiFiScan.ino
 *  Complete project details at our blog: https://RandomNerdTutorials.com/
 *  
 */

#include <WiFi.h>
#include <WiFiMulti.h>

WiFiMulti wifiMulti;

// WiFi connect timeout per AP. Increase when connecting takes longer.
const uint32_t connectTimeoutMs = 10000;

void setup(){
  Serial.begin(115200);
  delay(10);
  WiFi.mode(WIFI_STA);
  
  // Add list of wifi networks
  wifiMulti.addAP("ssid_from_AP_1", "your_password_for_AP_1");
  wifiMulti.addAP("ssid_from_AP_2", "your_password_for_AP_2");
  wifiMulti.addAP("ssid_from_AP_3", "your_password_for_AP_3");

  // WiFi.scanNetworks will return the number of networks found
  int n = WiFi.scanNetworks();
  Serial.println("scan done");
  if (n == 0) {
      Serial.println("no networks found");
  } 
  else {
    Serial.print(n);
    Serial.println(" networks found");
    for (int i = 0; i < n; ++i) {
      // Print SSID and RSSI for each network found
      Serial.print(i + 1);
      Serial.print(": ");
      Serial.print(WiFi.SSID(i));
      Serial.print(" (");
      Serial.print(WiFi.RSSI(i));
      Serial.print(")");
      Serial.println((WiFi.encryptionType(i) == WIFI_AUTH_OPEN)?" ":"*");
      delay(10);
    }
  }

  // Connect to Wi-Fi using wifiMulti (connects to the SSID with strongest connection)
  Serial.println("Connecting Wifi...");
  if(wifiMulti.run() == WL_CONNECTED) {
    Serial.println("");
    Serial.println("WiFi connected");
    Serial.println("IP address: ");
    Serial.println(WiFi.localIP());
  }
}

void loop(){
  //if the connection to the stongest hotstop is lost, it will connect to the next network on the list
  if (wifiMulti.run(connectTimeoutMs) == WL_CONNECTED) {
    Serial.print("WiFi connected: ");
    Serial.print(WiFi.SSID());
    Serial.print(" ");
    Serial.println(WiFi.RSSI());
  }
  else {
    Serial.println("WiFi not connected!");
  }
  delay(1000);
}

View raw code

Don’t forget to add a list of networks on the following lines. You can multiply those lines to add more networks.

wifiMulti.addAP("ssid_from_AP_1", "your_password_for_AP_1");
wifiMulti.addAP("ssid_from_AP_2", "your_password_for_AP_2");
wifiMulti.addAP("ssid_from_AP_3", "your_password_for_AP_3");

Note: if you want to test this project, but at the moment, you only have access to one network, you can create a hotspot with your smartphone and add the hotspot name and password to the list of available networks. I tested this with my iPhone and it worked perfectly (you may need to remove spaces and special characters from the hotspot name).

ESP32 with WiFiMulti Demonstration

After adding a list of networks to your code, you can upload it to your ESP32.

Open the Serial Monitor at a baud rate of 115200 and press the ESP32 RST button to restart the board.

First, it will show a list of nearby networks and corresponding RSSI. In my case, I have access to the first and third networks. In my case, the ESP32 connects to the iPhone network which is the strongest on the list (an RSSI closer to zero means a stronger signal).

If I remove the iPhone hotspot, the connection will be lost and it will connect to the next strongest network on the list.

Wrapping Up

In this tutorial, you learned how to use WiFiMulti with the ESP32 to add a list of networks that the ESP32 can connect to. It will connect to the network with the strongest signal (RSSI). If it loses connection with that network, it will automatically try to connect to the next network on the list.

We hope you find this tutorial useful. We have other tutorials related to Wi-Fi functions with the ESP32 that you may find useful:

• ESP32 Useful Wi-Fi Library Functions (Arduino IDE)
• [SOLVED] Reconnect ESP32 to Wi-Fi Network After Lost Connection

Learn more about the ESP32 with our resources:

• Learn ESP32 with Arduino IDE
• Build Web Servers with ESP32 and ESP8266
• Firebase Web App with ESP32 and ESP8266
• Free ESP32 Projects and Tutorials…

Thanks for reading.