HOME ESP32 ESP8266 ESP32-CAM RASPBERRY PI MICROPYTHON RPi PICO ARDUINO REVIEWS

ESP32 WebSocket Server: Control Outputs (Arduino IDE)

In this tutorial you’ll learn how to build a web server with the ESP32 using WebSocket communication protocol. As an example, we’ll show you how to build a web page to control the ESP32 outputs remotely. The output state is displayed on the web page and it updates automatically in all clients.

ESP32 WebSocket Server Control Outputs Arduino IDE

The ESP32 will be programmed using Arduino IDE and the ESPAsyncWebServer. We also have a similar WebSocket guide for the ESP8266.

If you’ve been following some of our previous web server projects like this one, you may have noticed that if you have several tabs (in the same or on different devices) opened at the same time, the state doesn’t update in all tabs automatically unless you refresh the web page. To solve this issue, we can use WebSocket protocol – all clients can be notified when a change occurs and update the web page accordingly.

This tutorial was based on a project created and documented by one of our readers (Stéphane Calderoni). You can read his excellent tutorial here.

Introducing WebSocket

A WebSocket is a persistent connection between a client and a server that allows bidirectional communication between both parties using a TCP connection. This means you can send data from the client to the server and from the server to the client at any given time. 

ESP32 ESP8266 WebSocket Server How it Works

The client establishes a WebSocket connection with the server through a process known as WebSocket handshake. The handshake starts with an HTTP request/response, allowing servers to handle HTTP connections as well as WebSocket connections on the same port. Once the connection is established, the client and the server can send WebSocket data in full duplex mode.

Using the WebSockets protocol, the server (ESP32 board) can send information to the client or to all clients without being requested. This also allows us to send information to the web browser when a change occurs.

This change can be something that happened on the web page (you clicked a button) or something that happened on the ESP32 side like pressing a physical button on a circuit.

Project Overview

Here’s the web page we’ll build for this project.

ESP32 WebSocket Server Toggle Outputs Project Overview
  • The ESP32 web server displays a web page with a button to toggle the state of GPIO 2;
  • For simplicity, we’re controlling GPIO 2 – the on-board LED. You can use this example to control any other GPIO;
  • The interface shows the current GPIO state. Whenever a change occurs on the GPIO state, the interface is updated instantaneously;
  • The GPIO state is updated automatically in all clients. This means that if you have several web browser tabs opened on the same device or on different devices, they are all updated at the same time.

How it Works?

The following image describes what happens when click on the “Toggle” button.

ESP32 WebSocket Web Server Update All Clients How it Works

Here’s what happens when you click on the “Toggle” button:

  1. Click on the “Toggle” button;
  2. The client (your browser) sends data via WebSocket protocol with the “toggle” message;
  3. The ESP32 (server) receives this message, so it knows it should toggle the LED state. If the LED was previously off, turn it on;
  4. Then, it sends data with the new LED state to all clients also through WebSocket protocol;
  5. The clients receive the message and update the led state on the web page accordingly. This allows us to update all clients almost instantaneously when a change happens.

Preparing Arduino IDE

We’ll program the ESP32 board using Arduino IDE, so make sure you have it installed in your Arduino IDE.

Installing Libraries – Async Web Server

To build the web server we’ll use the ESPAsyncWebServer library. This library needs the AsyncTCP library to work properly. Click the links below to download the libraries.

These libraries aren’t available to install through the Arduino Library Manager, so you need to copy the library files to the Arduino Installation Libraries folder. Alternatively, in your Arduino IDE, you can go to Sketch > Include Library > Add .zip Library and select the libraries you’ve just downloaded.

Code for ESP32 WebSocket Server

Copy the following code to your Arduino IDE.

/*********
  Rui Santos
  Complete project details at https://RandomNerdTutorials.com/esp32-websocket-server-arduino/
  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.
*********/

// Import required libraries
#include <WiFi.h>
#include <AsyncTCP.h>
#include <ESPAsyncWebServer.h>

// Replace with your network credentials
const char* ssid = "REPLACE_WITH_YOUR_SSID";
const char* password = "REPLACE_WITH_YOUR_PASSWORD";

bool ledState = 0;
const int ledPin = 2;

// Create AsyncWebServer object on port 80
AsyncWebServer server(80);
AsyncWebSocket ws("/ws");

const char index_html[] PROGMEM = R"rawliteral(
<!DOCTYPE HTML><html>
<head>
  <title>ESP Web Server</title>
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link rel="icon" href="data:,">
  <style>
  html {
    font-family: Arial, Helvetica, sans-serif;
    text-align: center;
  }
  h1 {
    font-size: 1.8rem;
    color: white;
  }
  h2{
    font-size: 1.5rem;
    font-weight: bold;
    color: #143642;
  }
  .topnav {
    overflow: hidden;
    background-color: #143642;
  }
  body {
    margin: 0;
  }
  .content {
    padding: 30px;
    max-width: 600px;
    margin: 0 auto;
  }
  .card {
    background-color: #F8F7F9;;
    box-shadow: 2px 2px 12px 1px rgba(140,140,140,.5);
    padding-top:10px;
    padding-bottom:20px;
  }
  .button {
    padding: 15px 50px;
    font-size: 24px;
    text-align: center;
    outline: none;
    color: #fff;
    background-color: #0f8b8d;
    border: none;
    border-radius: 5px;
    -webkit-touch-callout: none;
    -webkit-user-select: none;
    -khtml-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    user-select: none;
    -webkit-tap-highlight-color: rgba(0,0,0,0);
   }
   /*.button:hover {background-color: #0f8b8d}*/
   .button:active {
     background-color: #0f8b8d;
     box-shadow: 2 2px #CDCDCD;
     transform: translateY(2px);
   }
   .state {
     font-size: 1.5rem;
     color:#8c8c8c;
     font-weight: bold;
   }
  </style>
<title>ESP Web Server</title>
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="icon" href="data:,">
</head>
<body>
  <div class="topnav">
    <h1>ESP WebSocket Server</h1>
  </div>
  <div class="content">
    <div class="card">
      <h2>Output - GPIO 2</h2>
      <p class="state">state: <span id="state">%STATE%</span></p>
      <p><button id="button" class="button">Toggle</button></p>
    </div>
  </div>
<script>
  var gateway = `ws://${window.location.hostname}/ws`;
  var websocket;
  window.addEventListener('load', onLoad);
  function initWebSocket() {
    console.log('Trying to open a WebSocket connection...');
    websocket = new WebSocket(gateway);
    websocket.onopen    = onOpen;
    websocket.onclose   = onClose;
    websocket.onmessage = onMessage; // <-- add this line
  }
  function onOpen(event) {
    console.log('Connection opened');
  }
  function onClose(event) {
    console.log('Connection closed');
    setTimeout(initWebSocket, 2000);
  }
  function onMessage(event) {
    var state;
    if (event.data == "1"){
      state = "ON";
    }
    else{
      state = "OFF";
    }
    document.getElementById('state').innerHTML = state;
  }
  function onLoad(event) {
    initWebSocket();
    initButton();
  }
  function initButton() {
    document.getElementById('button').addEventListener('click', toggle);
  }
  function toggle(){
    websocket.send('toggle');
  }
</script>
</body>
</html>
)rawliteral";

void notifyClients() {
  ws.textAll(String(ledState));
}

void handleWebSocketMessage(void *arg, uint8_t *data, size_t len) {
  AwsFrameInfo *info = (AwsFrameInfo*)arg;
  if (info->final && info->index == 0 && info->len == len && info->opcode == WS_TEXT) {
    data[len] = 0;
    if (strcmp((char*)data, "toggle") == 0) {
      ledState = !ledState;
      notifyClients();
    }
  }
}

void onEvent(AsyncWebSocket *server, AsyncWebSocketClient *client, AwsEventType type,
             void *arg, uint8_t *data, size_t len) {
  switch (type) {
    case WS_EVT_CONNECT:
      Serial.printf("WebSocket client #%u connected from %s\n", client->id(), client->remoteIP().toString().c_str());
      break;
    case WS_EVT_DISCONNECT:
      Serial.printf("WebSocket client #%u disconnected\n", client->id());
      break;
    case WS_EVT_DATA:
      handleWebSocketMessage(arg, data, len);
      break;
    case WS_EVT_PONG:
    case WS_EVT_ERROR:
      break;
  }
}

void initWebSocket() {
  ws.onEvent(onEvent);
  server.addHandler(&ws);
}

String processor(const String& var){
  Serial.println(var);
  if(var == "STATE"){
    if (ledState){
      return "ON";
    }
    else{
      return "OFF";
    }
  }
  return String();
}

void setup(){
  // Serial port for debugging purposes
  Serial.begin(115200);

  pinMode(ledPin, OUTPUT);
  digitalWrite(ledPin, LOW);
  
  // Connect to Wi-Fi
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.println("Connecting to WiFi..");
  }

  // Print ESP Local IP Address
  Serial.println(WiFi.localIP());

  initWebSocket();

  // Route for root / web page
  server.on("/", HTTP_GET, [](AsyncWebServerRequest *request){
    request->send_P(200, "text/html", index_html, processor);
  });

  // Start server
  server.begin();
}

void loop() {
  ws.cleanupClients();
  digitalWrite(ledPin, ledState);
}

View raw code

Insert your network credentials in the following variables and the code will work straight away.

const char* ssid = "REPLACE_WITH_YOUR_SSID";
const char* password = "REPLACE_WITH_YOUR_PASSWORD";

How the Code Works

Continue reading to learn how the code works or skip to the Demonstration section.

Importing Libraries

Import the necessary libraries to build the web server.

#include <WiFi.h>
#include <AsyncTCP.h>
#include <ESPAsyncWebServer.h>

Network Credentials

Insert your network credentials in the following variables:

const char* ssid = "REPLACE_WITH_YOUR_SSID";
const char* password = "REPLACE_WITH_YOUR_PASSWORD";

GPIO Output

Create a variable called ledState to hold the GPIO state and a variable called ledPin that refers to the GPIO you want to control. In this case, we’ll control the on-board LED (that is connected to GPIO 2).

bool ledState = 0;
const int ledPin = 2;

AsyncWebServer and AsyncWebSocket

Create an AsyncWebServer object on port 80.

AsyncWebServer server(80);

The ESPAsyncWebServer library includes a WebSocket plugin that makes it easy to handle WebSocket connections. Create an AsyncWebSocket object called ws to handle the connections on the /ws path.

AsyncWebSocket ws("/ws");

Building the Web Page

The index_html variable contains the HTML, CSS and JavaScript needed to build and style the web page and handle client-server interactions using WebSocket protocol.

Note: we’re placing everything needed to build the web page on the index_html variable that we use on the Arduino sketch. Note that it may be more practical to have separated HTML, CSS and JavaScript files that then you upload to the ESP32 filesystem and reference them on the code.

Recommended reading: ESP32 Web Server using SPIFFS (SPI Flash File System)

Here’s the content of the index_html variable:

<!DOCTYPE HTML>
<html>
<head>
  <title>ESP Web Server</title>
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link rel="icon" href="data:,">
  <style>
  html {
    font-family: Arial, Helvetica, sans-serif;
    text-align: center;
  }
  h1 {
    font-size: 1.8rem;
    color: white;
  }
  h2{
    font-size: 1.5rem;
    font-weight: bold;
    color: #143642;
  }
  .topnav {
    overflow: hidden;
    background-color: #143642;
  }
  body {
    margin: 0;
  }
  .content {
    padding: 30px;
    max-width: 600px;
    margin: 0 auto;
  }
  .card {
    background-color: #F8F7F9;;
    box-shadow: 2px 2px 12px 1px rgba(140,140,140,.5);
    padding-top:10px;
    padding-bottom:20px;
  }
  .button {
    padding: 15px 50px;
    font-size: 24px;
    text-align: center;
    outline: none;
    color: #fff;
    background-color: #0f8b8d;
    border: none;
    border-radius: 5px;
    -webkit-touch-callout: none;
    -webkit-user-select: none;
    -khtml-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    user-select: none;
    -webkit-tap-highlight-color: rgba(0,0,0,0);
   }
   .button:active {
     background-color: #0f8b8d;
     box-shadow: 2 2px #CDCDCD;
     transform: translateY(2px);
   }
   .state {
     font-size: 1.5rem;
     color:#8c8c8c;
     font-weight: bold;
   }
  </style>
<title>ESP Web Server</title>
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="icon" href="data:,">
</head>
<body>
  <div class="topnav">
    <h1>ESP WebSocket Server</h1>
  </div>
  <div class="content">
    <div class="card">
      <h2>Output - GPIO 2</h2>
      <p class="state">state: <span id="state">%STATE%</span></p>
      <p><button id="button" class="button">Toggle</button></p>
    </div>
  </div>
<script>
  var gateway = `ws://${window.location.hostname}/ws`;
  var websocket;
  function initWebSocket() {
    console.log('Trying to open a WebSocket connection...');
    websocket = new WebSocket(gateway);
    websocket.onopen    = onOpen;
    websocket.onclose   = onClose;
    websocket.onmessage = onMessage; // <-- add this line
  }
  function onOpen(event) {
    console.log('Connection opened');
  }

  function onClose(event) {
    console.log('Connection closed');
    setTimeout(initWebSocket, 2000);
  }
  function onMessage(event) {
    var state;
    if (event.data == "1"){
      state = "ON";
    }
    else{
      state = "OFF";
    }
    document.getElementById('state').innerHTML = state;
  }
  window.addEventListener('load', onLoad);
  function onLoad(event) {
    initWebSocket();
    initButton();
  }

  function initButton() {
    document.getElementById('button').addEventListener('click', toggle);
  }
  function toggle(){
    websocket.send('toggle');
  }
</script>
</body>
</html>

CSS

Between the <style> </style> tags we include the styles to style the web page using CSS. Feel free to change it to make the web page look as you wish. We won’t explain how the CSS for this web page works because it is not relevant for this WebSocket tutorial.

<style>
  html {
    font-family: Arial, Helvetica, sans-serif;
    text-align: center;
  }
  h1 {
    font-size: 1.8rem;
    color: white;
  }
  h2 {
    font-size: 1.5rem;
    font-weight: bold;
    color: #143642;
  }
  .topnav {
    overflow: hidden;
    background-color: #143642;
  }
  body {
    margin: 0;
  }
  .content {
    padding: 30px;
    max-width: 600px;
    margin: 0 auto;
  }
  .card {
    background-color: #F8F7F9;;
    box-shadow: 2px 2px 12px 1px rgba(140,140,140,.5);
    padding-top:10px;
    padding-bottom:20px;
  }
  .button {
    padding: 15px 50px;
    font-size: 24px;
    text-align: center;
    outline: none;
    color: #fff;
    background-color: #0f8b8d;
    border: none;
    border-radius: 5px;
    -webkit-touch-callout: none;
    -webkit-user-select: none;
    -khtml-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    user-select: none;
    -webkit-tap-highlight-color: rgba(0,0,0,0);
   }
   .button:active {
     background-color: #0f8b8d;
     box-shadow: 2 2px #CDCDCD;
     transform: translateY(2px);
   }
   .state {
     font-size: 1.5rem;
     color:#8c8c8c;
     font-weight: bold;
   }
 </style>

HTML

Between the <body> </body> tags we add the web page content that is visible to the user.

<div class="topnav">
  <h1>ESP WebSocket Server</h1>
</div>
<div class="content">
  <div class="card">
    <h2>Output - GPIO 2</h2>
    <p class="state">state: <span id="state">%STATE%</span></p>
    <p><button id="button" class="button">Toggle</button></p>
  </div>
</div>

There’s a heading 1 with the text “ESP WebSocket Server”. Feel free to modify that text.

<h1>ESP WebSocket Server</h1>

Then, there’s a heading 2 with the “Output – GPIO 2” text.

<h2>Output - GPIO 2</h2>

After that, we have a paragraph that displays the current GPIO state.

<p class="state">state: <span id="state">%STATE%</span></p>

The %STATE% is a placeholder for the GPIO state. It will be replaced with the current value by the ESP32 at the time of sending the web page. The placeholders on the HTML text should go between % signs. This means that this %STATE% text is like a variable that will then be replaced with the actual value.

After sending the web page to the client, the state needs to change dynamically whenever there’s a change in the GPIO state. We’ll receive that information via WebSocket protocol. Then, JavaScript handles what to do with the information received to update the state accordingly. To be able to handle that text using JavaScript, the text must have an id that we can reference. In this case the id is state ( <span id=”state”>).

Finally, there’s a paragraph with the button to toggle the GPIO state.

<p><button id="button" class="button">Toggle</button></p>

Note that we’ve given an id to the button ( id=”button”).

JavaScript – Handling WebSockets

The JavaScript goes between the <script> </script> tags. It is responsible for initializing a WebSocket connection with the server as soon the web interface is fully loaded in the browser and handling data exchange through WebSockets.

<script>
  var gateway = `ws://${window.location.hostname}/ws`;
  var websocket;
  function initWebSocket() {
    console.log('Trying to open a WebSocket connection...');
    websocket = new WebSocket(gateway);
    websocket.onopen    = onOpen;
    websocket.onclose   = onClose;
    websocket.onmessage = onMessage; // <-- add this line
  }
  function onOpen(event) {
    console.log('Connection opened');
  }

  function onClose(event) {
    console.log('Connection closed');
    setTimeout(initWebSocket, 2000);
  }
  function onMessage(event) {
    var state;
    if (event.data == "1"){
      state = "ON";
    }
    else{
      state = "OFF";
    }
    document.getElementById('state').innerHTML = state;
  }

  window.addEventListener('load', onLoad);

  function onLoad(event) {
    initWebSocket();
    initButton();
  }

  function initButton() {
    document.getElementById('button').addEventListener('click', toggle);
  }

  function toggle(){
    websocket.send('toggle');
  }
</script>

Let’s take a look at how this works.

The gateway is the entry point to the WebSocket interface.

var gateway = `ws://${window.location.hostname}/ws`;

window.location.hostname gets the current page address (the web server IP address).

Create a new global variable called websocket.

var websocket;

Add an event listener that will call the onload function when the web page loads.

window.addEventListener('load', onload);

The onload() function calls the initWebSocket() function to initialize a WebSocket connection with the server and the initButton() function to add event listeners to the buttons.

function onload(event) {
  initWebSocket();
  initButton();
}

The initWebSocket() function initializes a WebSocket connection on the gateway defined earlier. We also assign several callback functions for when the WebSocket connection is opened, closed or when a message is received.

function initWebSocket() {
  console.log('Trying to open a WebSocket connection…');
  websocket = new WebSocket(gateway);
  websocket.onopen    = onOpen;
  websocket.onclose   = onClose;
  websocket.onmessage = onMessage;
}

When the connection is opened, we simply print a message in the console and send a message saying “hi”. The ESP32 receives that message, so we know that the connection was initialized.

function onOpen(event) {
  console.log('Connection opened');
  websocket.send('hi');
}

If for some reason the web socket connection is closed, we call the initWebSocket() function again after 2000 milliseconds (2 seconds).

function onClose(event) {
  console.log('Connection closed');
  setTimeout(initWebSocket, 2000);
}

The setTimeout() method calls a function or evaluates an expression after a specified number of milliseconds.

Finally, we need to handle what happens  when we receive a new message. The server (your ESP board) will either send a “1” or a “0” message. Accordingly to the received message, we want to display an “ON” or a “OFF” message on the paragraph that displays the state. Remember that <span> tag with id=”state”? We’ll get that element and set its value to ON or OFF.

function onMessage(event) {
  var state;
  if (event.data == "1"){
    state = "ON";
  }
  else{
    state = "OFF";
  }
  document.getElementById('state').innerHTML = state;
}

The initButton() function gets the button by its id (button) and adds an event listener of type ‘click’.

function initButton() {
  document.getElementById('button').addEventListener('click', toggle);
}

This means that when you click the button, the toggle function is called.

The toggle function sends a message using the WebSocket connection with the ‘toggle’ text.

function toggle(){
  websocket.send('toggle');
}

Then, the ESP32 should handle what happens when it receives this message – toggle the current GPIO state.

Handling WebSockets – Server

Previously, you’ve seen how to handle the WebSocket connection on the client side (browser). Now, let’s take a look on how to handle it on the server side.

Notify All Clients

The notifyClients() function notifies all clients with a message containing whatever you pass as a argument. In this case, we’ll want to notify all clients of the current LED state whenever there’s a change.

void notifyClients() {
  ws.textAll(String(ledState));
}

The AsyncWebSocket class provides a textAll() method for sending the same message to all clients that are connected to the server at the same time.

Handle WebSocket Messages

The handleWebSocketMessage() function is a callback function that will run whenever we receive new data from the clients via WebSocket protocol.

void handleWebSocketMessage(void *arg, uint8_t *data, size_t len) {
  AwsFrameInfo *info = (AwsFrameInfo*)arg;
  if (info->final && info->index == 0 && info->len == len && info->opcode == WS_TEXT) {
    data[len] = 0;
    if (strcmp((char*)data, "toggle") == 0) {
      ledState = !ledState;
      notifyClients();
    }
  }
}

If we receive the “toggle” message, we toggle the value of the ledState variable. Additionally, we notify all clients by calling the notifyClients() function. This way, all clients are notified of the change and update the interface accordingly.

if (strcmp((char*)data, "toggle") == 0) {
  ledState = !ledState;
  notifyClients();
}

Configure the WebSocket server

Now we need to configure an event listener to handle the different asynchronous steps of the WebSocket protocol. This event handler can be implemented by defining the onEvent() as follows:

void onEvent(AsyncWebSocket *server, AsyncWebSocketClient *client, AwsEventType type,
 void *arg, uint8_t *data, size_t len) {
  switch (type) {
    case WS_EVT_CONNECT:
      Serial.printf("WebSocket client #%u connected from %s\n", client->id(), client->remoteIP().toString().c_str());
      break;
    case WS_EVT_DISCONNECT:
      Serial.printf("WebSocket client #%u disconnected\n", client->id());
      break;
    case WS_EVT_DATA:
      handleWebSocketMessage(arg, data, len);
      break;
    case WS_EVT_PONG:
    case WS_EVT_ERROR:
      break;
  }
}

The type argument represents the event that occurs. It can take the following values:

  • WS_EVT_CONNECT when a client has logged in;
  • WS_EVT_DISCONNECT when a client has logged out;
  • WS_EVT_DATA when a data packet is received from the client;
  • WS_EVT_PONG in response to a ping request;
  • WS_EVT_ERROR when an error is received from the client.

Initialize WebSocket

Finally, the initWebSocket() function initializes the WebSocket protocol.

void initWebSocket() {
  ws.onEvent(onEvent);
  server.addHandler(&ws);
}

processor()

The processor() function is responsible for searching for placeholders on the HTML text and replace them with whatever we want before sending the web page to the browser. In our case, we’ll replace the %STATE% placeholder with ON if the ledState is 1. Otherwise, replace it with OFF.

String processor(const String& var){
  Serial.println(var);
  if(var == "STATE"){
    if (ledState){
      return "ON";
    }
    else{
      return "OFF";
    }
  }
}

setup()

In the setup(), initialize the Serial Monitor for debugging purposes.

Serial.begin(115200);

Set up the ledPin as an OUTPUT and set it to LOW when the program first starts.

pinMode(ledPin, OUTPUT);
digitalWrite(ledPin, LOW);

Initialize Wi-Fi and print the ESP32 IP address on the Serial Monitor.

WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED) {
  delay(1000);
  Serial.println("Connecting to WiFi..");
}

// Print ESP Local IP Address
Serial.println(WiFi.localIP());

Initialize WebSocket protocol by calling the initWebSocket() function created previously.

initWebSocket();

Handle Requests

Serve the text saved on the index_html variable when you receive a request on the root / URL – you need to pass the processor function as an argument to replace the placeholders with the current GPIO state.

server.on("/", HTTP_GET, [](AsyncWebServerRequest *request){
  request->send_P(200, "text/html", index_html, processor);
});

Finally, start the server.

server.begin();

loop()

The LED will be physically controlled on the loop().

void loop() {
  ws.cleanupClients();
  digitalWrite(ledPin, ledState);
}

Note that we all call the cleanupClients() method. Here’s why (explanation from the ESPAsyncWebServer library GitHub page):

Browsers sometimes do not correctly close the WebSocket connection, even when the close() function is called in JavaScript. This will eventually exhaust the web server’s resources and will cause the server to crash. Periodically calling the cleanupClients() function from the main loop()limits the number of clients by closing the oldest client when the maximum number of clients has been exceeded. This can be called every cycle, however, if you wish to use less power, then calling as infrequently as once per second is sufficient.

Demonstration

After inserting your network credentials on the ssid and password variables, you can upload the code to your board. Don’t forget to check if you have the right board and COM port selected.

After uploading the code, open the Serial Monitor at a baud rate of 115200 and press the on-board EN/RST button. The ESP IP address should be printed.

Open a browser on your local network and insert the ESP32 IP address. You should get access to the web page to control the output.

ESP32 WebSocket Server Toggle Outputs Project Overview

Click on the button to toggle the LED. You can open several web browser tabs at the same time or access the web server from different devices and the LED state will be update automatically in all clients whenever there’s a change.


Wrapping Up

In this tutorial you’ve learned how to set up a WebSocket server with the ESP32. The WebSocket protocol allows a full duplex communication between the client and the server. After initializing, the server and the client can exchange data at any given time.

This is very useful because the server can send data to the client whenever something happens. For example, you can add a physical button to this setup that when pressed notifies all clients to update the web interface.

In this example, we’ve shown you how to control one GPIO of the ESP32. You can use this method to control more GPIOs. You can also use the WebSocket protocol to send sensor readings or notifications at any given time.

We hope you’ve found this tutorial useful. We intend to create more tutorials and examples using the WebSocket protocol. So, stay tuned.

Learn more about the ESP32 with our resources:



SMART HOME with Raspberry Pi ESP32 and ESP8266 Node-RED InfluxDB eBook

SMART HOME with Raspberry Pi, ESP32, ESP8266 [eBook]

Learn how to build a home automation system and we’ll cover the following main subjects: Node-RED, Node-RED Dashboard, Raspberry Pi, ESP32, ESP8266, MQTT, and InfluxDB database DOWNLOAD »
Learn how to build a home automation system and we’ll cover the following main subjects: Node-RED, Node-RED Dashboard, Raspberry Pi, ESP32, ESP8266, MQTT, and InfluxDB database DOWNLOAD »

Recommended Resources

Build a Home Automation System from Scratch » With Raspberry Pi, ESP8266, Arduino, and Node-RED.

Home Automation using ESP8266 eBook and video course » Build IoT and home automation projects.

Arduino Step-by-Step Projects » Build 25 Arduino projects with our course, even with no prior experience!

What to Read Next…


Enjoyed this project? Stay updated by subscribing our newsletter!

161 thoughts on “ESP32 WebSocket Server: Control Outputs (Arduino IDE)”

  1. Hi RNT team!
    Another very interesting project…Thanks for keeping publishing the results of all your continuous electronics developing efforts!
    As a follow-up, how about a complementary project, this time one client connecting to and controlling the outputs pins of several (ESP32s) servers, all connected servers updating their similarly assigned pin status simultaneously, using the HTTP + the WebSockets protocols?
    Looking forward to hear from you, guys, soon!

    Reply

  2. Hi
    Interesting Article. I am attempting to run this on nodemcu (esp12-e) but get errors when trying to compile

    E:\Documents\Arduino\libraries\AsyncTCP-master\src/AsyncTCP.h:26:23: fatal error: sdkconfig.h: No such file or directory

    #include “sdkconfig.h”

    ^

    compilation terminated.

    Using library WiFi at version 1.2.7 in folder: C:\Program Files\WindowsApps\ArduinoLLC.ArduinoIDE_1.8.42.0_x86__mdqgnx93n4wtt\libraries\WiFi

    Using library AsyncTCP-master at version 1.1.1 in folder: E:\Documents\Arduino\libraries\AsyncTCP-master

    exit status 1

    Error compiling for board NodeMCU 1.0 (ESP-12E Module).

    Are there compatible libraries for the esp-12e???

    regards

    Meir

    Reply

      • Hi, Could you be more specific about the versions please?

        I think I have the latest versions of everything downloaded from links on your pages yet have the same error about sdkconfig.h

        I am running Arduino 1.8.13 and esp8266 V 2.7.4

        ResolveLibrary(sdkconfig.h)In file included from C:\Users\lou\Documents\Arduino\async_web\async_web.ino:10:0:

        -> candidates: []
        C:\Users\lou\Documents\Arduino\libraries\AsyncTCP-master\src/AsyncTCP.h:26:23: fatal error: sdkconfig.h: No such file or directory
        #include “sdkconfig.h”
        ^
        compilation terminated.
        Using library WiFi at version 1.2.7 in folder: C:\Program Files (x86)\Arduino\libraries\WiFi
        Using library AsyncTCP-master at version 1.1.1 in folder: C:\Users\lou\Documents\Arduino\libraries\AsyncTCP-master
        exit status 1
        Error compiling for board NodeMCU 1.0 (ESP-12E Module).

        Reply

      • Hi Rui – thanks for this wonderful article.

        Where does console.log(event.data) go? Will it output the data to the browser screen? If so, it does not appear on my browser and I need it for debugging.

        Also, how can I make event.data appear on the browser? I will be sending some other data from the websocket server and need to see it on the browser screen.

        Thanks a lot,
        Bernie

        Reply

  4. Amazing! I have made a lights automation in my house, so I need to know the state of each light via html page.
    How could I just switch the color of the button when the state changes, instead of ON and OFF words? For instante, yellow for ON and grey for OFF?

    Thank you very much.

    Reply

  6. Hi Rui and Sara, I don’t get much time to do your projects due to a medical issue, but I follow along with your postings. I just love the way you put them all together, especially with the explanation of how the code works and with additional reading references within the project. You both are a great asset to helping those interested in developing their knowledge of various systems and what is available. Thanks also to the readers who contribute. Many thanks to all concerned.

    Reply

  7. Hi Rui.
    to avoid digitalWrite (ledPin, led State); in every cycle I have made these changes to your code.
    do you see any problems in doing it in this way.

    bool event;
    unsigned long check = 1000;

    case WS_EVT_DATA:
    event = true;
    handleWebSocketMessage(arg, data, len)
    break;

    void loop() {

    if (millis() > check) {
    check = millis() + 1000;
    ws.cleanupClients();
    }

    if (event == true)
    {
    digitalWrite(ledPin, ledState);
    event = false;
    }

    }

    Reply

    • maybe this is a better way to handle millis and the roll over issue.

      long eventTimeout=(long)millis()+1000;

      void loop() {

      if((long)millis()-eventTimeout>=0)
      {
      ws.cleanupClients();
      Serial.println(“cleanup”);
      eventTimeout=(long)millis()+1000;
      }

      if (event == true)
      {
      digitalWrite(ledPin, ledState);
      event = false;
      //Serial.println(“event”);
      }
      }

      Reply

  8. Arduino : 1.8.13 (Windows 10), Carte : “NodeMCU-32S, 80MHz, 921600”
    C:\Users\Another\Documents\Arduino\ESP32_WebSocket_Server\ESP32_WebSocket_Server.ino: In function ‘String processor(const String&)’:

    ESP32_WebSocket_Server:201:1: error: control reaches end of non-void function [-Werror=return-type]

    }

    Reply

    • Change The String String processor to this.

      String processor(const String& var){
      Serial.println(var);
      if(var == “STATE”){
      if (ledState){
      return “ON”;
      }
      else{
      return “OFF”;
      }
      }
      return “”;
      }

      Reply

  9. Hi Rui and Sara.
    Thanks for another great tutorial. !!
    I’m running your code on an ESP32 devboard.

    When I refresh the website lot of times, the ESP32 board reboots and I get the error message, shown below.
    It only happens when I use my phone on a WiFi connection.
    When running the website on the computer there are no problems.
    Do you know why this is happening? or does anyone have a solution to this issue.

    CORRUPT HEAP: Bad head at 0x3ffcdc30. Expected 0xabba1234 got 0x3ffce05c
    assertion “head != NULL” failed: file “/home/runner/work/esp32-arduino-lib-builder/esp32-arduino-lib-builder/esp-idf/components/heap/multi_heap_poisoning.c”, line 214, function: multi_heap_free
    abort() was called at PC 0x40105487 on core 0

    regards JB.

    Reply

    • Hi JB,
      I got. the Same Problem. With my iphone sometimes the Webserver Even doesen‘t start. On a PC with Firefox, Chrome the ESP32 works fine.
      Dis you found the reason?
      Regards Chris

      Reply

  10. Hi, very nice project, I am trying to create more outputs and individual buttons for each of output, what is the easiest way to do that?

    Reply

  11. Hi Rui and Sara.
    Thanks for another great tutorial…
    i need to add more GPIO pins to control, please tell me where can i make modifications in this code.

    Reply

  12. This is another great project, I’ve done this project but would like to use websockets for sensor data. Are you planning on a project to do that. Like using a DHT22 sensor. Thanks again for all the great projects, very informative.

    Reply

    • Hi.
      Yes, you can use websockets for that.
      At the moment, we don’t have any tutorial with sensor readings and websockets. But, I’ll add that to my list.
      Regards,
      Sara

      Reply

  14. Hello Sara and Rui,

    I am an avid user of your learning pages. When someone asks me on the forums where they can educate themselves, I never hesitate to inform your site.

    I have 2 small questions regarding this tutorial:

    How to add a second button assigned to a second other ESP32 output.

    How to invert the output state of the pin when starting the ESP32 (if there is a power failure, subsequently, when the power returns, the state of the pins will be on). I went to see the tutorial with the relays and the, that’s what I’m looking for but the concern is that the method used for this tutorial does not update the events instantly.

    Many thanks to you for your work.

    Reply

  15. Bonjour Sara et Rui,
    Merci pour votre tutorial tres explicite.
    J’utilise ce mode pour mon projet actuel ESP8266. C’est parfait…
    Pour finir ce dernier, pourriez-vous m’aider?
    Je souhaite integrer un servo sg90 dans le sketch “ESP Web Server”.
    J’ai: 1- un fichier HTML (un jeu de ma création) qui doit se connecter avec “ESP Web Server” à un servo. Quand le jeu est terminé, et que cela est gagné!!..le jeu declenche un basculement du servo et ouvre un verrou. c’est un jeu en extérieur donc “ESP Web Server” est indispensable.
    Merci de votre aide dans la mesure du possible

    Reply

  16. Rui and Sara,
    Wow, what a great job in explaining the topic. Your postings have been extraordinarily helpful. What a great reference. I just started to learn about arduino and now ESP32 and your pages and videos have been of great help!
    THANK YOU!

    Reply

  17. Hi there, I separated the files into HTML/JS/CSS files to clean it all up a bit. Didn’t change any of the functionality and only had to change a couple of lines. You can download the files at: github.com/rayjamesdev/ESP32-WebSocket-Server-Control-Outputs-Separate-Files

    Good Luck Have Fun! 🙂

    Reply

  18. Hi

    Any suggestions for getting an esp32 plus websockets plus GSM module like the sim7600 working?

    Looks like websockets is easily supported for wifi…but cannot figure out for GSM modules.

    Thanks

    Phil

    Reply

  19. Hi, I loaded the code as is to ESP32 Huzzah.
    Only changed the Led pin to 13 and my credentials of course.

    I can open the page on 3 devices but clicking the button does nothing.
    At some several seconds later I can see the console to show “STATUS”.

    I have updated the AsyncTCP also the ESPAsyncWebServer libraries but no luck.

    What could be the issue…?

    Reply

  20. By the way, the stae of the GPIO does not change at the web pages either.
    Reloading the pasges works ok, just the gpio handling is not.

    Reply

  21. Thank you for your great tutorials!!

    I have loaded the example to a ESP32 Huzzah. Changed the credentials & Gpio from 2 to 13. I can open the page on 3 devices but clicking the button does nothing on either device (laptop, phone).

    I mean, the state of the GPIO does not change on the hardware and at the web pages either.

    Reloading the pages refresh quickly; it is just the Gpio handling is not.

    Several seconds later the console show “STATUS”. it looks like the ESP32 is lagging or not responsive.

    What could be the cause…?

    Reply

  22. Now I have tested with Explorer browser too. It is the same thing.

    I see some code in the code: like:

    console.log(‘Trying to open a WebSocket connection…’);

    But at the Arduino terminal this never shows.
    Where is supposed I will see these messages…?

    console.log(‘Trying to open a WebSocket connection…’);
    console.log(‘Connection opened’);
    console.log(‘Connection closed’);

    Regards.

    Reply

    • Hi Bob, I have exactly the same question! Although I have worked through this tutorial and eveything works, I don’t yet understand what a console is and where one finds it. I would like to do that to be able to fully understand Rui and Sara’s detailed explanations about how the code works.

      If you, or anyone else, knows of any beginners’ guides to seeing these console messages (on PlatformIO on Visual Studio Code on Mac) that would be great. So far I’ve found nothing that I can understand on Google.

      Reply

  23. Well, after a full day and with the help of my teammates we find out the reason.

    It happen the JavaScript code was not executing. The variable “gateway” crashed the browser side. By some unknown reason it not passed the content after your “`” delimiters. At the end it complained by a JavaScript error (Uncaught SyntaxError: Unexpected end of input).

    The fix was to replace your delimiters ( ` ) by apostrophe delimiters ( ‘ ) and to concatenate the “window.location.hostname” :

    var gateway = ‘ws://’ + window.location.hostname + ‘/ws’;

    After that, it worked great.

    Reply

      • Hello Sara,
        Hello all,

        here is my solution.

        Now there is no more error and it works fine.
        Uncaught SyntaxError: Missing } in template expression (at (index):84:25)

        var ip = “192.168.178.35”, wsf = “ws:\/\/”, wsl = “\/ws”;
        var gateway = wsf + ip + wsl;

        I got the same error. Only STATUS was output in the serial monitor.

        With this I can finally update my solar page with ESP32 variables on all browsers (crome,edge,opera,.). Such a websocket is great.

        Many greetings and many thanks Sara. This is one of the best pages I have found. Always happy to help 🙂

        Chris

        Reply

    • I have the same problem, the server opens, but the LED does not light up. I tried turning on yours as you said but it is not working. Can you help me?

      Reply

  24. Hello, Rui and Sara. I see a lot of questions here – How do I add multiple buttons? What parts of the code should I edit? Could you make changes to this project so that it has two buttons? I think a lot of people will thank you for that. With great respect for your work.

    Reply

  26. Hello
    excellent tutorial.
    I have even expanded it to 5 buttons as shared by Alex. Thank you.
    I use 3 phones and 2 PCs and they connect perfectly and update as long as it’s on the same local network. However, in one of the phones I have put the public IP of my ESP32 device and in another phone the domain name of my place of installation.
    In both phones I see the web page generated by the server but when I press the button “to activate a certain output, it is not reflected on any side of the connected clients.
    Is it a problem with my modem? I already removed the antivirus and canceled the shields.
    I defined the NAT with port 8080 and the fixed address that I assigned to the WiFi module.
    But there is no client / server communication.
    Can you give me an advice or solution to the external control?
    Thanks

    Reply

  28. Olá, muito obrigado pelos tutoriais. Gostaria de saber como alterar as credenciais do wifi sem ter que alterar o código para compilar no ESP32. Existe uma forma de fazer isso? Com a biblioteca WifiManager acho que é possível.

    Obrigado!

    Reply

  30. Excellent information Rui and Sara Santos, I have a question about WebSocket. There is a possibility that the DHT22 sensor values instead of going to a web page via html. Can those values be sent to another ESP32 with the same communication protocol and can it be observed on the Arduino Ide’s serial monitor?

    Greetings and thanks for sharing your work.

    Reply

  31. Hi Rui and Sara,

    So I was experimenting a project with the ESP8266. I came to know that there are ‘websocket’ and just ‘socket’ and that they are different. I couldn’t find anything that says these ‘sockets’ are supported with ESP8266.

    I was building a server in ESP8266 to receive some JSON file to be processed from another server that I build using ‘socket’ in flask. But the ESP8266 was not receiving any data. I believe it was due to ‘websocket’ being used in ESP and ‘socket’ being used in flask, looks like the sent data was not compatible enough to be received.

    Before using ESP to receive the data, I was using a serve made in flask. So I know that data was being sent and received. I wanted to try a different approach to my project by using ESP.

    Is there any libraries that support the use of ‘socket’?

    Please help.

    Reply

  33. Hi Rui and Sara,
    Have you guys seen or heard of “Canvas-gauges” ? I’m trying to use those gauges to read continuously from analog pin on ESP32 using Websockets, with Arduino IDE. Ive managed to generate the gauge & customize it, set a value and it animates ok, but the websocket to get a live reading I cant figure out. I’d like to see a tutorial on it. here is an example of one type :
    https://rawgit.com/Mikhus/canvas-gauges/master/examples/issue-63.html# you can click on numbers at top to see needle move to that reading.
    https://canvas-gauges.com/documentation/examples/ some more they’re free and lots of options, animation options on the needle, Radial, Linear types etc.
    The Arduino seems maybe limited but close, I had to put the Javascript in the arduino sketch, it’ll display the gauge on a served web page after loading into ESP32, but I can’t get the analog reading from a potentiometer to give live update.
    Would you guys be interested in doing a tutorial on something like that? or do you know of someone that would help me out?
    Thanks

    Reply

    • Hi Stephen.
      Yes. That was something that was on my to-do list.
      I’ll try to come up with an example web server with gauges soon.
      Thanks for sharing.
      Regards,
      Sara

      Reply

    • Hi Stephen,

      To get a live reading in the first example you gave all you have to do is update the guagePS.value whenever you call a new reading event by the addEventListener.

      Tony

      Reply

      • Thanks Tony, I have way under-estimated the complexity of websockets. I thought if I modified an existing live updating potentiometer to text & bar display output which works, instantly updating on the web page, to these neat canvas-gauges I’d have it.

        code: https://akuzechie.blogspot.com/2021/01/esp32-websocket-server-sending.html
        I havent understood everything about that javascript code.
        All the support code around websockets and Javascript I’m ignorant to. I thought I could just put the variable assigned to the ESP32 pin to change the value of the gauge and that would be enough, as of today I’m not smart enough to figure that out, but I keep looking and reading. The addEventListener im studying now.

        Reply

  34. Thanks for this great article Rui Santos.

    I want (eventually) to make a sort of own home automation system and this is probably the best ‘base’ for it to control it via a website.

    However, my intention is to use two kind of ‘boxes’, each with its own ESP32, one type with sensors, and one with relays in it. And to make it flexible, I like any sensor (or combination) to be able to control any relay.

    Do I have to use a single webserver (with websockets as in your article), and let the sensor/relay boxes communicate with the webserver also via HTTP_GET (and maybe HTTP_POST) message? Or do I have to do the sensor/relaybox and webserver communication via something else than a WebServer? (I prefer to use WIFI only for all communication).

    Hope this question is not much out of context.

    Reply

    • Hi.
      If you need to control multiple ESP32 boards via the same web interface, I suggest using MQTT for communication and Node-RED for the dashboard.
      Regards,
      Sara

      Reply

  35. FYI, the code works with ESP32 C3, only if you make the following change.
    In the file StringArray.h of the ESPAsyncWebServer library comment line 131.
    From
    delete it;
    to

    // delete it;

    bool remove(const T& t){
    auto it = _root;
    auto pit = _root;
    while(it){
    if(it->value() == t){
    if(it == _root){
    _root = _root->next;
    } else {
    pit->next = it->next;
    }

    if (_onRemove) {
    _onRemove(it->value());
    }

    131 line // delete it;
    return true;
    }
    pit = it;
    it = it->next;
    }
    return false;

    }

    Reply

    • Thanks, I had this issue and your fix worked. I started an issue on the GitHub so maybe it will get fixed at the source.

      Reply

  36. Anyone getting errors such as this
    c:/users/cruis/appdata/local/arduino15/packages/esp32/tools/xtensa-esp32-elf-gcc/gcc8_4_0-esp-2021r2/bin/../lib/gcc/xtensa-esp32-elf/8.4.0/../../../../xtensa-esp32-elf/bin/ld.exe: C:\Users\cruis\Documents\Arduino\libraries\ESPAsyncWebServer\src/AsyncWebSocket.cpp:1273: undefined reference to `SHA1Update’
    I have tried different boards with the same issue. Have they broken things again with firmware updates

    Reply

  38. Hello Rui and Sara.
    I need your help with some direction to add some functionality using Websockets.
    1.- Authentication before establishing a communication by Websockets.
    2.- Navigate between several pages without losing the connection when going from one page to another.
    First of all, Thanks

    Reply

  39. Hi! I need to display the time in the browser, via a websocket.

    html

    javascript
    document.getElementById(“dateTime”).innerHTML = ???;

    How i can to send the time parameter to javascript?

    Code
    const char *ntpServer = “pool.ntp.org”;
    const long gmtOffset_sec = 10800; // GMT+3
    const int daylightOffset_sec = 3600;

    void printLocalTime()
    {
    struct tm timeinfo;
    if (!getLocalTime(&timeinfo))
    {
    Serial.println(“Couldn’t get the time”);
    return;
    }
    Serial.println(&timeinfo, “%d %B %H:%M:%S”);

    Reply

  40. have just loaded the Firebased Websocket-server-Arduino and this is what i get
    Connecting to WiFi..
    Connecting to WiFi..
    Connecting to WiFi..
    Connecting to WiFi..
    Connecting to WiFi..
    Connecting to WiFi..
    Connecting to WiFi..
    ets Jun 8 2016 00:22:57

    rst:0x1 (POWERON_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
    flash read err, 1000
    ets_main.c 371
    ets Jun 8 2016 00:22:57

    rst:0x10 (RTCWDT_RTC_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
    configsip: 0, SPIWP:0xee
    clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
    mode:DIO, clock div:1
    load:0x3fff0018,len:4
    load:0x3fff001c,len:1216
    ho 0 tail 12 room 4
    load:0x40078000,len:10944
    load:0x40080400,len:6388
    entry 0x400806b4
    Connecting to WiFi..
    Connecting to WiFi..
    Connecting to WiFi..
    Connecting to WiFi..
    Connecting to WiFi..
    Connecting to WiFi..
    Connecting to WiFi..
    any help appreciated

    Reply

  41. GREAT CODE! Thank you!!!

    However… You left out a very important piece. I put that in and tested it and all is well. Sometimes, you want to have a switch on the board and turn on the LED (or relay or whatever) with that switch. When doing that, you also want to update the web client(s). It works. There is a little bit of extra code to be put into loop (and a couple of other places) to make this happen. Connect switch from the switchPin to ground to toggle the LED and report to clients.

    Would be so good if you would update your code with this. Then, you would have a complete demo of WebSockets operation.

    (as a global)
    const int switchPin = 23; // Or whatever you like.

    (in setup)
    pinMode(switchPin, INPUT_PULLUP); // Connect to ground to toggle.

    (in handleWebSocketMessage)
    if (strcmp((char*)data, “toggle”) == 0) {
    ledState = !ledState;
    digitalWrite(ledPin, ledState); // This line added for better responsiveness of the LED
    notifyClients();
    }

    (new loop routine)
    void loop() {

    ws.cleanupClients();

    if (digitalRead(switchPin) == LOW){ // Switch pressed?
    delay(50); // connect debounce
    if (digitalRead(switchPin) == LOW) { // Switch still pressed?
    ledState = !ledState;
    digitalWrite(ledPin, ledState);
    notifyClients();
    while (digitalRead(switchPin) == LOW); // Wait for unpress.
    delay(50); // disconnect debounce
    }
    }
    }

    Reply

  42. Hi Rui and Sara!
    A question about transferring data from the websocket server to the client.
    How to properly transfer two data streams to the client?
    I need some kind of identifier to distinguish them!

    Sketch:
    void loop() {
    if (abcde…)
    {
    ws.textAll(String(temperature1));
    }
    if (edcba…)
    {
    ws.textAll(String(temperature2));
    }
    }

    JavaScript:
    function onMessage(event) {
    document.getElementById(“datetemp1”).innerHTML = event.data;
    document.getElementById(“datetemp2”).innerHTML = event.data;
    }

    Could you give an any example? Many thanks!

    Reply

  43. hello.
    very nice exemples .
    I search how to add “esp32-websocket-server-arduino”
    to ” esp32-esp-now-wi-fi-web-server”.
    I have problem to understant how to do this !
    thx

    Reply

  45. Hi Sara,
    I followed the ESPWebSocket Server as above and uploaded using Arduino IDE to my
    ESP32-DevKitC NodeMCU WiFi WLAN CP2102 ESP32-WROOM-32D Microcontroller Bluetooth Module Development Board. I then opened my computer browser and inserted the IP displayed for my esp32 in my Arduino serial monitor . The Toggle button was displayed but when toggled did not activate the on board led. I also opened a browser on my iPhone and again the toggle was displayed but did not activate the led when pressed but the toggle on my computer changed immediately. The same happened when I used the computer browser – the button on the iPhone changed as expected.

    Thinking that the in-built led might have a different port to “2” on this board I changed the sketch using

    pinMode(LED_BUILTIN, OUTPUT);
    digitalWrite(LED_BUILTIN, LOW);

    to eliminate the specified port. This compiled but as before the LED did not activate when the toggle was pressed but both browser toggles duplicated the display of the other browser each time a toggle was pressed.
    Any ideas how to solve this one ?

    Reply

    • It inverts the state of the LED on the server-side (ESP32) after a Websocket message was received from a client telling to change state (i.e., ‘toggle’).

      Reply

  47. In the example above, the data passed is “toggle”. Where is this value stored? I want to further parse the value.

    For example:
    String x;
    x = “toggle”;
    x[0] = ‘t’
    x[1] = ‘o’ etc

    So I need to know the variable name and type. I’m thinking this must be a Json type but can’t find the actual item.

    thanks much
    Barry

    Reply

    • Further info: Here is the html. There is a table with 2 buttons. The user may select A, or B, or A*B (2 independent transactions). My program will decide what to do with based on the returned id=”A1″ or “B1”. Actually there are multiple lines in the table so the general form is “An” where n=0..9

      html code follows:

      2

      Reply

  49. Having failed at posting an code snippet, let me ask different question. How do I do a Serial.print of the data IN TO JS, and OUT OF JS?

    I understand now that the HTML –> JS for checkboxes is either a 1/0 for each box. The “id” identifies which checkbox. I see that JS has a FOR loop to look at each box, then translate the 1/0 to “toggle”.

    Is it possible to have the JS do NO processing and just send the JS input to JS output? That would be simpler. What would that code be?

    Reply

  50. What is the difference between a synchronous and asynchronous web server? Can WebSocket be used in both? Also, is it possible to get Wifi Manager for an asynchronous web server?

    Reply

  51. Hi Rui and Sara,
    Thanks for the excellent explanation and code.
    I’m trying to access the ESP-32 from outside my home network.
    I have set up port forwarding on my router from port 8083 to port 80.
    It appears that the websocket still sends from the browser on port 80 so I changed line 107 from:
    var gateway = ws://${window.location.hostname}/ws;
    to:
    var gateway = ‘ws://’ + window.location.hostname + ‘:8083/ws’;
    and it now works but it’s not a very elegant solution.
    Can you give a suggestion for a better fix?

    Reply

    • Sara is my good teacher.
      I am always grateful and wish you good health.

      I really like John’s method, but there is a disadvantage that websocket does not work in the internal network.

      If you want to use it normally both externally and internally,
      you can change one Arduino content in addition to your opinion.

      AsyncWebServer server(80);
      to
      AsyncWebServer server(8083);

      This will work for now both internally and externally.

      As someone who had the same problem for a long time, I appreciate your hint.

      Written with Google Translate

      Reply

  52. Hi Sara and Rui, Could you please consider publishing an example of this websocket tutorial that has 2 led outputs, 2 webpage inputs, plus 2 physical button inputs. These are great tutorials but when it comes to expanding them beyond 1 input and 1 output it is sometimes hard to know where to expand the HTML, CSS, java, etc code and where not too. Several people have requested this above and in some of the other tutorials coments too and I think this would tie together nicely several of your other examples. Thankyou.

    Reply

    • Hello Ford,

      Why don’t you buy the book they publish like I did. It explains everything you are looking for and a whole lot more, it is not expensive. Everything can’t be free, what Rui and Sara do is hard work and a lot of time.

      Reply

      • I did mate, a year ago, and the book has been great in learning webservers. But the book does not cover expanding beyond more than one input output with both web and physical buttons. The comments from Mike above covers some of it, thanks, but I still think it would be great if the RNT team could do a complete example in their teaching style.

        Reply

    • Hi.

      I’ll add to my to-do list: multiple buttons with websocket that can also be controlled by physical buttons.

      Maybe a better idea would be a guide that covers multiple types of buttons: momentary switches, toggle buttons, slider switches, ON/Off buttons, and radio buttons.

      I already have projects lined up for the next month. So, it may take a little while.

      Thanks for supporting our work.

      Don’t forget, that as one of our customers, if you have specific issues, you can ask questions in our private forum: https://rntlab.com/forum/

      Regards,
      Sara

      Reply

  54. Hi Rui and Sara
    Perhaps this comment is duplicaat..
    Thanks a lot for the nice and clear explanation of the script.
    uploading the script to a esp32 the compiler says
    C:\Users\Beheerder\Desktop\Arduino Schetsen Local\0ARuiSantos\ESPWebsocketServer\ESPWebSocketServer\ESPWebSocketServer.ino: In function ‘void loop()’:
    ESPWebSocketServer:227:6: error: ‘class AsyncWebSocket’ has no member named ‘cleanupClients’
    ws.cleanupClients();
    ^
    C:\Users\Beheerder\Desktop\Arduino Schetsen Local\0ARuiSantos\ESPWebsocketServer\ESPWebSocketServer\ESPWebSocketServer.ino: In function ‘String processor(const String&)’:
    ESPWebSocketServer:196:1: error: control reaches end of non-void function [-Werror=return-type]
    }
    ^
    cc1plus.exe: some warnings being treated as errors
    Please advice what’s wrong…

    Thanks,

    wouter

    Reply

  56. Hello. Thank you, this is a really good example, it works very fast.
    How can I display DHT values on this page without refreshing the page?
    How to scale the number of buttons? Thank you in advance.

    Reply

  57. Hello,
    Nice presentation of a project applicable for home automation. How can we add several buttons to it with the display of the state (On/Off) in the button? The idea being to control the lighting and other objects having an all or nothing operation. I still managed to put the code (html; css; js) on the spiff and connect to the Access Point of your project presented, it’s already a good start :).
    Thank you for the help that will be given to me.

    Reply

  58. Drops COM port after flash,
    Hello, i’m using a ESP32 DEVKITV1, powered and flashed VIA USB from my PC.
    i don’t get any errors when flashing, but it drops COM3 as soon as it’s loaded and i can no longer view the board in the serial monitor.

    i’ve tried this code a few times, after it flashes the COM port drops and i can’t contact the board.
    Holding EN brings it back and i can flash different software on to it.

    not sure what i’m missing here.

    Reply

    • SOLVED
      Although my USB connection was fine for my smaller projects, the issue was coming from the USB cable itself.

      I was using a USB extension, as my PC is my TV. bringing the USB right to the PC resolved the issue and everything works as intended.

      Reply

  60. I try to swap HTML&Co to SPIFFS (added #include “SPIFFS.h”, copied HTML&Co to SPIFFS) but code doesn´t work:

    // Route for root / web page
    server.on(“/”, HTTP_GET, [](AsyncWebServerRequest *request){
    request->send_P(SPIFFS, “text/html”, “/index_html”, processor);
    });

    Reply

    • Hi.
      What happens exactly when you say it doesn’t work?
      Do you get any error messages on the Serial Monitor?
      What about the web browser?

      Regards,
      Sara

      Reply

    • Hi!
      Your code contains errors. Here’s the right one
      server.on(“/”, HTTP_GET, [](AsyncWebServerRequest *request)
      { request->send(SPIFFS, “/index.html”, “text/html”, false, processor); });

      Reply

  61. I get a compiler error:
    C:\Users\43677\Documents\Arduino\esp32-websocket-server-arduino_SPIFFS_20230114163048\esp32-websocket-server-arduino_SPIFFS_20230114163048.ino: In lambda function:
    C:\Users\43677\Documents\Arduino\esp32-websocket-server-arduino_SPIFFS_20230114163048\esp32-websocket-server-arduino_SPIFFS_20230114163048.ino:228:66: error: no matching function for call to ‘AsyncWebServerRequest::send_P(fs::SPIFFSFS&, const char [10], const char [12], String (&)(const String&))’
    request->send_P(SPIFFS, “text/html”, “/index_html”, processor);
    ^
    In file included from C:\Users\43677\Documents\Arduino\esp32-websocket-server-arduino_SPIFFS_20230114163048\esp32-websocket-server-arduino_SPIFFS_20230114163048.ino:11:
    c:\Users\43677\Documents\Arduino\libraries\ESPAsyncWebServer-master\src/ESPAsyncWebServer.h:243:10: note: candidate: ‘void AsyncWebServerRequest::send_P(int, const String&, const uint8_t*, size_t, AwsTemplateProcessor)’
    void send_P(int code, const String& contentType, const uint8_t * content, size_t len, AwsTemplateProcessor callback=nullptr);
    ^~~~~~
    c:\Users\43677\Documents\Arduino\libraries\ESPAsyncWebServer-master\src/ESPAsyncWebServer.h:243:10: note: no known conversion for argument 1 from ‘fs::SPIFFSFS’ to ‘int’
    c:\Users\43677\Documents\Arduino\libraries\ESPAsyncWebServer-master\src/ESPAsyncWebServer.h:244:10: note: candidate: ‘void AsyncWebServerRequest::send_P(int, const String&, const char*, AwsTemplateProcessor)’
    void send_P(int code, const String& contentType, PGM_P content, AwsTemplateProcessor callback=nullptr);
    ^~~~~~
    c:\Users\43677\Documents\Arduino\libraries\ESPAsyncWebServer-master\src/ESPAsyncWebServer.h:244:10: note: no known conversion for argument 1 from ‘fs::SPIFFSFS’ to ‘int’

    exit status 1

    Compilation error: no matching function for call to ‘AsyncWebServerRequest::send_P(fs::SPIFFSFS&, const char [10], const char [12], String (&)(const String&))’

    Reply

  62. Hi All,

    can someone please tell me what the purpose of the following code is? It is located within the handleWebSocketMessage() function.

    data[len] = 0;

    does this set the last element to 0 or something? What is the purpose of this line anyway?.

    BR

    Reply

  63. Thanks for the program, which is working across PC browsers. But, the program is not working in mobile phone android chrome browser.

    Reply

      • Yes, the PC browsers and mobile browsers on the same WiFi network.
        All PC browsers are working well for the above program.
        But, on the android mobile chrome browser it is showing “The site can’t be reached”. “http://192.168.130/ is unreachable. ERR_ADDRESS_UNREACHABLE”.

        Reply

  64. If I want a second page for some configuration values, should the second .html file have another .js file, or can two pages use on .js and share the websockets ?

    Reply

    • Hi.
      Thanks for the suggestion.
      I’ll add it to my to-do list.
      Maybe I can publish it next month.
      Regards,
      Sara

      Reply

  66. tried the code on the wemos D1 R32 board ,
    I get many warning errors and exit status 1 err and stops compiler.
    using IDE 2.1.0
    I also get many warnings with similar ESP8266 ESP8266WiFi.h and WebSocketServer.h
    on wemos D1 R1 but compiler finishes and pgm runs with rather large HTML portion…
    WebSocketServer.h is great , but no work on ESP32 board

    Reply

    • Hi.
      First, you need to install all libraries mentioned in the code.
      I don’t recommend using Arduino IDE 2.0. I still recommend using the legacy version.
      Which errors do you get?
      Regards,
      Sara

      Reply

  67. (contains solution)
    A few years down the line, this doesn’t seem to work so well anymore…leading to various errors during compilation.
    It seems that both the Websocket library as well as the ESP32 Async linrary are not maintained so well.
    Errors I got were for instance:

    “mbedtls_md5_starts throws error”/”undefined reference to mbedtls_md5_starts'"
    Solution for that is to rename the instance of    mbedtls_md5_startstombedtls_md5_starts_ret` in the Webauthentication.cpp file in the libraries/ESPASyncWebserver/src directory
    Another error was “class IPAddres Public printable’ -> edit libraries\ESPAsyncWebServer-master\src\AsyncWebSocket.cpp to replace “return IPAddress(0U)” by “return IPAddress(0ul)” or “return IPAddress((uin32_t) 0u)”

    Now it could be that maybe I had an old library (I thought I was up to date), but if others have this problem as well, perhaps this will help you

    Reply

  69. I have build many of your applications and very pleased but hav e broblems
    Using IDE 2.0.0 Windows 10 ESP32 Dev Module. Latest libs. Good quality cables.
    But got the same problem here as I wrote 27/8 in ESP32 WebSocket Server: Display Sensor Readings.
    Generating function prototypes…
    C:\Users\Peter\AppData\Local\Arduino15\packages\esp32\tools\xtensa-esp32-elf-gcc\esp-2021r2-patch5-8.4.0/bin/xtensa-esp32-elf-g++ -DHAVE_CONFIG_H -DMBEDTLS_CONFIG_FILE=”mbedtls/esp_config.h” -DUNITY_INCLUDE_CONFIG_H -DWITH_POSIX -D_GNU_SOURCE -DIDF_VER=”v4.4.5″ -DESP_PLATFORM -D_POSIX_READER_WRITER_LOCKS -IC:\Users\Peter\AppData\Local\Arduino15\packages\esp32\hardware\esp32\2.0.11/tools/sdk/esp32/include/newlib/platform_include –
    D:\Documents\Arduino\Esp32-WebSocketControlOutput-Phone\Esp32-WebSocketControlOutput-Phone.ino: In function ‘void loop()’:
    D:\Documents\Arduino\Esp32-WebSocketControlOutput-Phone\Esp32-WebSocketControlOutput-Phone.ino:180:6: error: ‘class AsyncWebSocket’ has no member named ‘cleanupClients’; did you mean ‘hasClient’?
    ws.cleanupClients();
    ^~~~~~~~~~~~~~
    hasClient

    Using library SPIFFS at version 2.0.0 in folder: C:\Users\Peter\AppData\Local\Arduino15\packages\esp32\hardware\esp32\2.0.11\libraries\SPIFFS
    Using library FS at version 2.0.0 in folder: C:\Users\Peter\AppData\Local\Arduino15\packages\esp32\hardware\esp32\2.0.11\libraries\FS
    Using library WiFi at version 2.0.0 in folder: C:\Users\Peter\AppData\Local\Arduino15\packages\esp32\hardware\esp32\2.0.11\libraries\WiFi
    Using library AsyncTCP at version 1.1.4 in folder: D:\Documents\Arduino\libraries\AsyncTCP
    Using library ESP Async WebServer at version 1.2.2 in folder: D:\Documents\Arduino\libraries\ESPAsyncWebServer-master
    Using library credentials in folder: D:\Documents\Arduino\libraries\credentials (legacy)
    exit status 1

    Compilation error: ‘class AsyncWebSocket’ has no member named ‘cleanupClients’; did you mean ‘hasClient’?

    Reply

  70. I am new to C++ and am having a difficult time understanding 1) the parameters passed to handleWebSocketMessage, 2) the AwsFrameInfo, 3) the conditional used in that function, and 4) the data[len] code.

    Could someone break these down?

    Reply

  71. randomnerdtutorials.com/esp32-websocket-server-arduino/
    Bonjour Sara
    Merci pour vos publications.
    Votre tuto fonctionne parfaitement sur PC, mais impossible de transmettre des données sur IPHONE e tablette Android. Ils se connectent mais ne reçoivent pas de données
    Cordialement et merci

    Reply

  73. Greeting!
    I thank the authors for the code and excellent descriptions of individual parts of the code. I am a beginner with ESP32. I tried to compile the code for the ESP32 WebSocket Server. I got a series of errors with the following descriptions:

    error: ‘mbedtls_md5_starts_ret’ was not declared in this scope; did you mean ‘mbedtls_md5_starts’?
    error: ‘mbedtls_md5_update_ret’ was not declared in this scope; did you mean ‘mbedtls_md5_update’?
    error: ‘ets_printf’ was not declared in this scope; did you mean ‘vswprintf’?

    I tried with old and latest libraries. The result is the same.
    Where can I look for an error?

    Reply

  75. Thank you for a fantastic series of articles on ESP32/EPS8266 networking. I jumped from MicroPython to C++ due performance issues (MP wasn’t able to keep up with real time events; well, expected). Rewriting from MP to C++ isn’t that straightforward; there are always these “small” details here and there. ESP32 documentation helps a lot, but it is much easier to grab your project, run it, learn how it is done, adapt my code accordingly.

    (I am glad that Google led me to this site.)

    Reply

  76. Thank you for this great tutorial!
    I just have one problem: Android doesn’t allow me to connect to HTTPS, only to HTTPS – is there any way to add support for SSL/TSL?

    Reply

  77. I get this error:

    c:\Users\Betterparts\Documents\Arduino\libraries\ESPAsyncWebServer\src\WebAuthentication.cpp: In function ‘bool getMD5(uint8_t*, uint16_t, char*)’:
    c:\Users\Betterparts\Documents\Arduino\libraries\ESPAsyncWebServer\src\WebAuthentication.cpp:74:3: error: ‘mbedtls_md5_starts_ret’ was not declared in this scope; did you mean ‘mbedtls_md5_starts’?
    74 | mbedtls_md5_starts_ret(&_ctx);
    | ^~~~~~~~~~~~~~~~~~~~~~
    | mbedtls_md5_starts
    c:\Users\Betterparts\Documents\Arduino\libraries\ESPAsyncWebServer\src\WebAuthentication.cpp:75:3: error: ‘mbedtls_md5_update_ret’ was not declared in this scope; did you mean ‘mbedtls_md5_update’?
    75 | mbedtls_md5_update_ret(&_ctx, data, len);
    | ^~~~~~~~~~~~~~~~~~~~~~
    | mbedtls_md5_update
    c:\Users\Betterparts\Documents\Arduino\libraries\ESPAsyncWebServer\src\WebAuthentication.cpp:76:3: error: ‘mbedtls_md5_finish_ret’ was not declared in this scope; did you mean ‘mbedtls_md5_finish’?
    76 | mbedtls_md5_finish_ret(&_ctx, _buf);
    | ^~~~~~~~~~~~~~~~~~~~~~
    | mbedtls_md5_finish

    exit status 1

    Compilation error: exit status 1

    Reply

  78. I copied your code and it compiled and loaded. I get the message “Connecting to WiFi” on the serial monitor.
    However, I do not see the esp32c on the network.

    Reply

Leave a Comment

Download Our Free eBooks and Resources

Get instant access to our FREE eBooks, Resources, and Exclusive Electronics Projects by entering your email address below.