The Ultimate Guide to ESPAsyncWebServer WebSockets

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Introduction

When it comes to building IoT projects or web applications that require real-time communication, WebSockets have proven to be a reliable solution. In addition, the ESP32 microcontroller has become a popular choice among developers for IoT projects due to its power and versatility. In this article, we will explore the ESPAsyncWebServer WebSocket library, which allows you to establish real-time communication between the ESP32 and a web browser.

What are WebSockets?

WebSockets are a protocol that allows for real-time communication between a server and a client. Unlike HTTP, which is a request-response protocol, WebSockets provide a full-duplex communication channel that stays open between the client and the server. This means that both the client and server can send data to each other at any time.

The advantages of WebSockets over traditional HTTP requests are numerous. For example, WebSockets allow for faster communication with less overhead. They also eliminate the need for constant polling, which can put a strain on server resources.

What is ESPAsyncWebServer?

ESPAsyncWebServer is an Arduino library that provides a web server for the ESP32. It is built on top of the AsyncTCP library and supports HTTP and HTTPS protocols. ESPAsyncWebServer is designed to be lightweight and easy to use, making it an ideal choice for IoT projects.

What is ESPAsyncWebServer WebSocket?

ESPAsyncWebServer WebSocket is a library that allows you to establish real-time communication between the ESP32 and a web browser using the WebSocket protocol. This library is built on top of the ESPAsyncWebServer library and provides an easy-to-use interface for working with WebSockets.

Installation

The first step in using ESPAsyncWebServer WebSocket is to install it. Here are the steps:

Open the Arduino IDE.
Go to Sketch > Include Library > Manage Libraries.
In the search bar, type “ESPAsyncWebServer”.
Select the latest version of the library and click “Install”.
Repeat the above steps for “ESPAsyncTCP” and “ArduinoJson” libraries.

Once the installation is complete, you can begin using the library in your project.

Creating a WebSocket Server

The first step in using ESPAsyncWebServer WebSocket is to create a WebSocket server. Here’s how:

Step 1: Include the Required Libraries

To use ESPAsyncWebServer WebSocket, you need to include the following libraries:

<ESPAsyncWebServer.h>
<ESPAsyncTCP.h>
<ArduinoJson.h>

Step 2: Define the WebSocket Handler

To define the WebSocket handler, you need to create a function that will be called whenever a WebSocket connection is established. This function should accept a single parameter of type AsyncWebSocket * and return void. Here’s an example:

void onWebSocketEvent(AsyncWebSocket *server, AsyncWebSocketClient *client, AwsEventType type, void *arg, uint8_t *data, size_t len) {// Handle WebSocket events here}

In this example, we are defining a function called “onWebSocketEvent” that will be called whenever a WebSocket event occurs. The function accepts an AsyncWebSocket pointer, an AsyncWebSocketClient pointer, an AwsEventType, a void pointer, a uint8_t pointer, and a size_t. The last two parameters are optional and are used for receiving data.

Step 3: Create the WebSocket Server

To create the WebSocket server, you need to create an instance of the AsyncWebSocket class. Here’s an example:

AsyncWebSocket ws("/ws");

In this example, we are creating an instance of the AsyncWebSocket class and passing “/ws” as the path for the WebSocket. This means that the WebSocket URL will be “ws://<ip-address>/ws”.

Step 4: Add the WebSocket Handler

To add the WebSocket handler, you need to call the onEvent function of the AsyncWebSocket instance and pass the WebSocket handler function as a parameter. Here’s an example:

ws.onEvent(onWebSocketEvent);

In this example, we are calling the onEvent function of the AsyncWebSocket instance and passing the “onWebSocketEvent” function as a parameter. This means that the “onWebSocketEvent” function will be called whenever a WebSocket event occurs.

Step 5: Start the WebSocket Server

To start the WebSocket server, you need to call the begin function of the AsyncWebSocket instance and pass the web server instance as a parameter. Here’s an example:

server.addHandler(&ws);

In this example, we are adding the WebSocket handler to the web server instance by calling the addHandler function and passing the AsyncWebSocket instance as a parameter.

Creating a WebSocket Client

Now that we have created a WebSocket server, let’s create a WebSocket client that can connect to it. Here’s how:

Step 1: Include the Required Libraries

To use the WebSocket client, you need to include the following libraries:

<WebSocketsClient.h>
<ArduinoJson.h>

Step 2: Define the WebSocket Client

To define the WebSocket client, you need to create an instance of the WebSocketsClient class. Here’s an example:

WebSocketsClient webSocket;

Step 3: Connect to the WebSocket Server

To connect to the WebSocket server, you need to call the connect function of the WebSocketsClient instance and pass the WebSocket URL as a parameter. Here’s an example:

webSocket.connect("ws://<ip-address>/ws");

In this example, we are connecting to the WebSocket server at “ws://<ip-address>/ws”.

Step 4: Handle WebSocket Events

To handle WebSocket events, you need to define a function that will be called whenever a WebSocket event occurs. This function should accept a single parameter of type WStype_t and return void. Here’s an example:

void onWebSocketEvent(WStype_t type, uint8_t *payload, size_t length) {// Handle WebSocket events here}

In this example, we are defining a function called “onWebSocketEvent” that will be called whenever a WebSocket event occurs. The function accepts a WStype_t, a uint8_t pointer, and a size_t. The last two parameters are optional and are used for receiving data.

Step 5: Add the WebSocket Event Handler

To add the WebSocket event handler, you need to call the onEvent function of the WebSocketsClient instance and pass the WebSocket event handler function as a parameter. Here’s an example:

webSocket.onEvent(onWebSocketEvent);

In this example, we are calling the onEvent function of the WebSocketsClient instance and passing the “onWebSocketEvent” function as a parameter. This means that the “onWebSocketEvent” function will be called whenever a WebSocket event occurs.

Step 6: Send Data to the WebSocket Server

To send data to the WebSocket server, you need to call the sendTXT function of the WebSocketsClient instance and pass the data as a parameter. Here’s an example:

webSocket.sendTXT("Hello, world!");

In this example, we are sending the string “Hello, world!” to the WebSocket server.

Handling WebSocket Events

Now that we have created a WebSocket server and client, let’s explore the different WebSocket events that you can handle.

onConnect

The onConnect event is called when a WebSocket connection is established. Here’s an example of how to handle this event:

void onWebSocketEvent(AsyncWebSocket *server, AsyncWebSocketClient *client, AwsEventType type, void *arg, uint8_t *data, size_t len) {if (type == WS_EVT_CONNECT) {Serial.println("WebSocket client connected");}}

In this example, we are checking if the event type is WS_EVT_CONNECT and printing a message to the serial monitor when a WebSocket client connects.

onDisconnect

The onDisconnect event is called when a WebSocket connection is closed. Here’s an example of how to handle this event:

void onWebSocketEvent(AsyncWebSocket *server, AsyncWebSocketClient *client, AwsEventType type, void *arg, uint8_t *data, size_t len) {if (type == WS_EVT_DISCONNECT) {Serial.println("WebSocket client disconnected");}}

In this example, we are checking if the event type is WS_EVT_DISCONNECT and printing a message to the serial monitor when a WebSocket client disconnects.

onData

The onData event is called when data is received from the WebSocket client. Here’s an example of how to handle this event:

void onWebSocketEvent(AsyncWebSocket *server, AsyncWebSocketClient *client, AwsEventType type, void *arg, uint8_t *data, size_t len) {if (type == WS_EVT_DATA) {String message = String((char *)data);Serial.println("Received message: " + message);}}

In this example, we are checking if the event type is WS_EVT_DATA, converting the data to a String, and printing the message to the serial monitor.

onError

The onError event is called when an error occurs with the WebSocket connection. Here’s an example of how to handle this event:

void onWebSocketEvent(AsyncWebSocket *server, AsyncWebSocketClient *client, AwsEventType type, void *arg, uint8_t *data, size_t len) {if (type == WS_EVT_ERROR) {Serial.println("WebSocket error");}}

In this example, we are checking if the event type is WS_EVT_ERROR and printing a message to the serial monitor.

FAQ

What is the difference between HTTP and WebSockets?

HTTP is a request-response protocol that is used for sending data between a client and a server. WebSockets, on the other hand, provide a full-duplex communication channel that stays open between the client and the server. This means that both the client and server can send data to each other at any time.

What are the advantages of using WebSockets?

WebSockets provide several advantages over traditional HTTP requests. For example, WebSockets allow for faster communication with less overhead. They also eliminate the need for constant polling, which can put a strain on server resources.

What is ESPAsyncWebServer?

ESPAsyncWebServer is an Arduino library that provides a web server for the ESP32. It is built on top of the AsyncTCP library and supports HTTP and HTTPS protocols.

What is ESPAsyncWebServer WebSocket?

How do I install ESPAsyncWebServer WebSocket?

To install ESPAsyncWebServer WebSocket, you need to open the Arduino IDE, go to Sketch > Include Library > Manage Libraries, search for “ESPAsyncWebServer”, select the latest version of the library, and click “Install”. Repeat the same process for “ESPAsyncTCP” and “ArduinoJson” libraries.

How do I create a WebSocket server?

To create a WebSocket server using ESPAsyncWebServer WebSocket, you need to define the WebSocket handler, create the WebSocket server, add the WebSocket handler, and start the WebSocket server. You can find more information on how to do this in the article.

How do I create a WebSocket client?

To create a WebSocket client using ESPAsyncWebServer WebSocket, you need to define the WebSocket client, connect to the WebSocket server, handle WebSocket events, and send data to the WebSocket server. You can find more information on how to do this in the article.