Real-time communication with WebSockets: a hands-on JS roundup
Jul 14, 2025 am 01:45 AM
WebSockets enable real-time, two-way communication for web apps. To use them in JavaScript: 1) Create a WebSocket instance with new WebSocket('wss://your-websocket-server.com') and handle connection states via events like onopen. 2) Send messages using socket.send() and receive them using socket.onmessage. 3) Handle errors and disconnections with onerror and onclose, and implement reconnection logic with exponential backoff. 4) Close connections properly with socket.close() to avoid leaks, especially in SPAs.
If you're looking to build real-time features into your web app — like live chat, notifications, or collaborative tools — WebSockets are a solid choice. Unlike HTTP requests that end after a response, WebSockets keep a persistent connection open between the client and server, allowing for instant two-way communication. In this post, I’ll walk through how to get started with WebSockets using JavaScript, from basic setup to handling messages and reconnecting gracefully.
Setting up a WebSocket connection in JS
Getting a WebSocket connection up and running is pretty straightforward on the client side. You just need to create a new WebSocket instance and pass it the URL of your server:
const socket = new WebSocket('wss://your-websocket-server.com');Use ws:// for unencrypted connections and wss:// for secure ones (which you should always aim for in production).
Once created, the WebSocket goes through a few ready states: connecting, open, closing, and closed. You can check these via socket.readyState, but more commonly, you'll respond to them using event handlers like onopen:
socket.onopen = () => {
console.log('WebSocket connection established');
};You don’t need a lot of boilerplate to start — just connect, listen for events, and send data when needed.
Sending and receiving messages
WebSockets aren’t useful unless they can actually exchange data. Once the connection is open, you can send messages using the .send() method:
socket.send('Hello server!');On the receiving end, you use the onmessage handler:
socket.onmessage = (event) => {
console.log('Message from server:', event.data);
};Messages can be text, JSON strings, or even binary data like blobs or array buffers. Most of the time, though, you’ll be sending structured data as JSON:
// Sending an object
socket.send(JSON.stringify({ type: 'chat', message: 'Hi there' }));
// Receiving and parsing
socket.onmessage = (event) => {
const data = JSON.parse(event.data);
console.log(data.type, data.message);
};Make sure both client and server agree on the format — otherwise, things can get confusing fast.
Handling errors and disconnections
Real-time connections can drop for all kinds of reasons — network issues, server crashes, timeouts. It’s important to handle those gracefully.
To catch errors, set an onerror handler:
socket.onerror = (error) => {
console.log('WebSocket error:', error);
};And for disconnections, use onclose:
socket.onclose = (event) => {
console.log('Connection closed:', event.reason);
};But what if you want to automatically reconnect? Here's a simple pattern:
- Use a flag to track whether a reconnection is already in progress.
- Wait a short delay before retrying, and increase it each time (exponential backoff).
- Optionally limit the number of retries.
Example:
let reconnectAttempts = 0;
const maxRetries = 5;
function connect() {
const socket = new WebSocket('wss://your-websocket-server.com');
socket.onclose = () => {
if (reconnectAttempts < maxRetries) {
setTimeout(() => {
reconnectAttempts ;
connect();
}, 1000 * Math.pow(2, reconnectAttempts));
}
};
}
connect();This helps avoid hammering the server while still giving users a chance to reconnect without refreshing the page.
Closing connections properly
When you no longer need the connection — say, when a user logs out or navigates away — make sure to close it explicitly:
socket.close();
This frees up resources and prevents memory leaks. If you’re building a single-page app (SPA), remember to clean up WebSocket instances when components unmount or routes change.
Also, avoid creating multiple WebSocket instances unnecessarily. A single connection usually suffices unless you have separate services or protocols to communicate with.
That's basically it. WebSockets might seem tricky at first, especially if you're used to request-response patterns, but once you get the hang of opening the connection, sending/receiving messages, and handling disconnects, it becomes pretty intuitive. There are also libraries like Socket.IO or SignalR that add extra layers (like fallback transports and rooms), but knowing how raw WebSockets work gives you a better foundation to understand and debug those higher-level tools.
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