ReactJS is a popular JavaScript library used for building user interfaces. One of the biggest advantages of ReactJS is its ability to create dynamic and real-time applications. This is made possible through the use of WebSockets, which allow for real-time communication between a client and a server.

In this article, we will explore the use of WebSockets with ReactJS to build real-time applications. We will cover what WebSockets are, how they work, and how to implement them in a ReactJS application. We will also discuss some use cases for real-time applications and some best practices for building them.

What are WebSockets?

WebSockets are a communication protocol that allows for real-time communication between a client and a server. Unlike HTTP, which is a request/response protocol, WebSockets provide a persistent connection between the client and server. This means that data can be sent between the client and server in real-time without the need for the client to constantly request data.

WebSockets are based on TCP (Transmission Control Protocol), which is a reliable, connection-oriented protocol. This means that messages sent over a WebSocket connection are guaranteed to be delivered in the order they were sent and without errors.

How do WebSockets work?

WebSockets use a handshake process to establish a connection between the client and server. This handshake process starts with an HTTP request from the client to the server, requesting an upgrade to the WebSocket protocol. If the server supports WebSockets, it will respond with a 101 status code, indicating that the upgrade was successful.

Once the WebSocket connection is established, data can be sent between the client and server using the send() method on the WebSocket object. The server can also send data to the client using the send() method.

To close the WebSocket connection, either the client or server can send a close message using the close() method on the WebSocket object.

Implementing WebSockets in a ReactJS application

To implement WebSockets in a ReactJS application, we need to use a WebSocket library. One of the most popular WebSocket libraries for ReactJS is Socket.IO.

Socket.IO is a JavaScript library that enables real-time, bidirectional, and event-based communication between the browser and the server. It uses WebSocket as the primary transport mechanism but can fallback to other transports, such as long-polling, if WebSocket is not available.

To use Socket.IO in a ReactJS application, we need to install the library using npm:

npm install

We can then create a WebSocket connection in our ReactJS component using the following code:

import io from '';

const socket = io('http://localhost:3000');

function App() {
   // ...

In this code, we import the io function from the library and create a WebSocket connection to the server running on http://localhost:3000.

We can then use the socket object to send and receive data between the client and server. For example, we can listen for events on the socket object using the on() method:

socket.on('message', (data) => {
   console.log('Received message:', data);

In this code, we listen for a 'message' event on the socket object and log the data received from the server to the console.

We can also send data to the server using the emit() method:

socket.emit('message', 'Hello server!');

In this code, we send a 'message' event to the server with the data 'Hello server!'.

Real-time application use cases

Real-time applications are becoming increasingly popular as users expect instant updates and notifications. Some examples of real-time applications include:

  1. Chat applications: Real-time chat applications use WebSockets to enable real-time messaging between users. With WebSockets, messages can be sent and received instantly, without the need for users to constantly refresh the page or send requests to the server. Examples of real-time chat applications include WhatsApp, Slack, and Facebook Messenger.
  1. Multiplayer games: Multiplayer games also rely on real-time communication to enable players to interact with each other in real-time. With WebSockets, game data can be sent between players and the server instantly, allowing for real-time gameplay. Examples of multiplayer games that use WebSockets include Fortnite, Minecraft, and Among Us.

  2. Collaborative editing: Real-time collaboration tools like Google Docs and Microsoft Office 365 use WebSockets to enable real-time editing between multiple users. With WebSockets, changes made by one user can be instantly reflected on the screens of all other users, allowing for seamless collaboration.

  3. Financial applications: Real-time financial applications like stock market trackers and trading platforms rely on real-time data to enable traders to make informed decisions in real-time. With WebSockets, real-time data can be streamed to traders, allowing them to make quick decisions based on the latest information.

Best practices for building real-time applications

Building real-time applications with WebSockets can be challenging, especially when it comes to scalability and performance. Here are some best practices for building real-time applications:

  1. Use a WebSocket library: Rather than implementing WebSockets from scratch, use a WebSocket library like Socket.IO to handle the low-level details of WebSocket communication.

  2. Use a scalable server architecture: Real-time applications can quickly become overwhelmed with traffic, so it's important to use a scalable server architecture that can handle a large number of WebSocket connections. Consider using a load balancer and multiple servers to distribute the load.

  3. Optimize data transmission: Real-time applications can generate a lot of data, so it's important to optimize data transmission to reduce latency and bandwidth usage. Consider using compression techniques like gzip to reduce the size of data transmitted over the WebSocket connection.

  4. Implement security measures: Real-time applications can be vulnerable to security threats like XSS (Cross-Site Scripting) attacks and SQL injection attacks. Implement security measures like input validation, parameterized queries, and encryption to protect against these threats.


WebSockets are a powerful technology that enables real-time communication between a client and server. By using WebSockets with ReactJS, we can build dynamic and real-time applications that provide a seamless user experience. Whether you're building a chat application, a multiplayer game, or a collaborative editing tool, WebSockets can help you build a real-time application that meets the needs of your users. By following best practices like using a WebSocket library, optimizing data transmission, and implementing security measures, you can build a scalable and performant real-time application that delivers real-time updates and notifications to your users.