How to Build a Chat application with ReactJS, NodeJS, and Socket.IO?


Have you ever wondered how to develop a chat application using ReactJS and NodeJS but haven’t found an appropriate and easy tutorial? If yes, then you’ve clicked the right tutorial!

There are so many blogs available on this topic but what I found is the difficulty level. The technical jargon of the blogs was intimidating, and I was looking for an easy tutorial. And that’s when I thought of writing this blog with a simple flow.

In this blog, we will learn about Socket.IO and build a demo chat application with the help of ReactJS and NodeJS.

What is Socket.IO?

It’s impossible to corner when we are discussing chat applications or transferring real-time data!

So what is this Socket.IO?

Keeping it short: Socket.IO is a Javascript library built for real-time data transfer.

Things to be kept in mind regarding Socket.IO:

  • Javascript library used for real-time apps
  • Enables bidirectional real-time communication between servers & clients
  • It uses WebSocket protocol with polling as a fallback
  • It’s not just a wrapper for WebSocket; it provides various features as broadcasting, async I/O, and storing data of the respective client.
  • Socket.IO requires libraries on the client and server sides.

Tutorial Goal: What are we building?

The Flow of Building Chat App

After watching the video, you might have got an idea of what we are building. Let’s see the technical concept and flow behind the room, and we will then move to high-level development flow.

The Flow of Building Chat App

You have seen what we are building. Let’s see a high-level overview of the development flow.

1. Server Side

  • We will deal with the server-side first.
  • Install all the dependencies concerned with the back-end.
  • Establish socket connection at server-side.
  • getRoom API for room ID

2. Client-Side

  • On the client-side, after creating the client application, install its dependencies.
  • Establish basic socket connection at client-side.
  • Add socket listeners.
  • Build front-end components for UI.

Steps: How to Build a Chat Application with ReactJS, NodeJS, and Socket.IO

Follow these steps to build a chat application using ReactJs, NodeJs, and Socket.IO.


Getting Started

Create a new folder, navigate to the folder, and generate a package.json

mkdir chat-app-backend
cd chat-app-backend

npm init -y

Install Dependencies

npm i express cors

Basic Server Setup

For that, create a file named app.js and start coding with me! Now in that, import required packages.

const express = require("express");
const path = require("path");
const http = require("http");
const app = express();
// Creating http server
const server = http.createServer(app);
const PORT = process.env.PORT || 3000;
console.log('Server listening to PORT: ', PORT);

Socket.IO Connection

It’s time to add to the server.

We have already installed it in the above step. Now, make it require in the app.js, and then we are good to go for implementing

const activeUsers = new Set();
let roomId = "";
// Creating socket connection
// A socket is one endpoint of a two-way communication link between two programs running on the network.
// ... An endpoint is a combination of an IP address and a port number.
io.on("connection", (socket) => {
 // Joining room for conversation
 socket.on("JOIN_ROOM", (room) => {
   roomId = room;
  // To emit an event from your client, use the “emit” function  
  // on the socket object
  // To handle these events, use the “on” function on the	
  // socket object
  // Create an event NEW_MESSAGE. It will be used to 
  // send messages from the client-side.                
  // Listen to NEW_MESSAGE for receiving new messages
 socket.on("NEW_MESSAGE", (msg) => {"NEW_MESSAGE", msg);
 // To disconnect participant from room
 // And remove specific user from object
 socket.on("disconnect", () => {
   // Triggering this event disconnects user"user disconnected", socket.userId);


  • When a user sends a message in the room, we want all the users to receive that message.
  • We will import and create its object.
  • The cors parameter is used for executing the code locally and handling cors errors.
  • After establishing the socket connection, we will let the user join the room with its unique roomId.
  • For sending and receiving messages through, we will use event. NEW_MESSAGE event will listen to new messages in the joined room. Make sure to use the same event at the client side for sending messages.
  • On disconnecting the socket, the user is disconnected from the room and removed from the object.

API for Room ID- getRoom

Create a file named users.js and use this code to generate and send room ID.

const { v4: uuidv4 } = require('uuid');
const getRoom = (req, res) => {
 const randomGenUniqueName = uuidv4();
 res.status(200).send({ roomUrl: randomGenUniqueName });

Moving towards the Front-end part.


Getting Started

Create client folder named chat-app-frontend using the below command-

npx create-react-app chat-app-frontend
cd chat-app-frontend

Install Socket.IO for Client

npm i

Client-Side Socket.IO connection

I have created helper.js and will establish the client socket connection in that file itself. Further, I will import the function wherever I need to send and receive the messages at the client-side.

Open helper.js and use this code to establish a connection.

import socketIOClient from "";
// socketIOClient connects front-end to with socket backend URL
export const socket = socketIOClient(process.env.REACT_APP_SOCKET_URL, {
 transports: [ "websocket" ],
 reconnectionAttempts: 20,
 reconnectionDelay: 5000

Front-end Components

Let’s make front-end components for our UI.

One by one, we will edit the file. Kindly replace your files with the following code. Keep in mind that we will focus on the Socket.IO.

There are two scenarios on our Login page-
1. Create Room: When the user has to create a room and share the room id with other users to join the room and start a conversation.

2. Join Room: If you have a room id, click the Join Room by filling in the required text fields.

The UI for Login would be something like this-

UI for Login

Create a file named Login.js. And use this logic while clicking the button.

handleOnJoinRoom() will be called when the user clicks Join Room. setItemInStorage() will store the username in the local storage.

If the user clicks Create Room, an API will be called, giving you the roomId. Again, store the username in the local storage.

const handleOnJoinRoom = () => {
   if (roomId.trim().length > 0) {
     setItemInStorage('user', {
       name: userName,
 const onLoginClick = (e) => {
   if (roomType === ROOM_TYPE.createRoom) {
     toastSuccess('Room created!!');
       .then((res) => {
         if (res && res.roomUrl) {
           setItemInStorage('user', {
             name: userName,
       .catch((err) => {
   } else {

Once the user is logged in, they are redirected to the Dashboard.

The UI for Dashboard will be something like this-

UI for Dashboard

Create Dashboard.js and replace it with this code.

import React, { useEffect, useState } from 'react';
import { Container } from 'reactstrap';
import ChatContainer from '../components/chat-components/ChatContainer';
import MessageBar from '../components/chat-components/MessageBar';
import Header from '../components/common/layout/Header';
import { socket } from '../utils/helper';
const DashBoard = (props) => {
 const { params } = props.match;
 const [messages, setMessages] = useState([]);
 useEffect(() => {
   // Trigger JOIN_ROOM with unique room ID
   socket.emit('JOIN_ROOM', params.roomId);
 }, [params.roomId]);
 useEffect(() => {
   // Trigger 'NEW_MESSAGE' event
   // Message received in the event NEW_MESSAGE
   socket.on('NEW_MESSAGE', (message) => {
     setMessages((prevState) => [...prevState, message]);
 }, []);
 return (
    <Header roomId={params.roomId} />
     <Container fluid className="p-0">
       <Container className="d-flex flex-column chat-container">
         <div className="scroll-content pl-2 pr-2">
           <ChatContainer messages={messages} />
           <MessageBar />
export default DashBoard;


1. The first useEffect() will trigger JOIN_ROOM with a unique room_id. You might wonder what emit does? The Socket.IO API is inspired by the Node.js Event Emitter, which means you can emit events on one side and register listeners on the other.

2. The second useEffect() will trigger NEW_MESSAGE. Due to this event, we can receive the messages and then can use setMessages() to store them.

Moving on two other two components-
ChatContainer.js – Used for displaying chat
MessageBar.js – Text Field for typing a message and then sending it

Open ChatContainer.js and write this code.
We will display the message and sender’s name in the chat room.

import React, { useEffect, useRef } from 'react';
import PropTypes from 'prop-types';
import { getItemFromStorage } from '../../utils/helper';
const ChatContainer = ({ messages }) => {
 const { name } = getItemFromStorage('user');
 const messagesEnd = useRef(null);
 useEffect(() => {
   // used for scrolling the chat smoothly
   messagesEnd.current.scrollIntoView({ behavior: 'smooth' });
 }, [messages]);
 return (
     {messages && messages.length
       ?, index) => (
             className={`msg-container msg-container-${
               message.userName === name ? 'right' : 'left'
             <div className="msg-header">
              <span	className="msg-user-name">      
             <div className="msg-content">
               <span className="msg-text">
       : null}
     <div style={{ float: 'left', clear: 'both' }} ref={messagesEnd} />
ChatContainer.propTypes = {
 messages: PropTypes.array.isRequired,
export default ChatContainer;

Open MessageBar.js .

Import socket from helper.js

import { socket } from '../utils/helper';

Write this logic for sending the message on the button click.

const [ value, setValue ] = useState("");
const { name } = getItemFromStorage("user");
// On submit
const handleSubmit = (msg) => {
  // Trigger NEW_MESSAGE with object containing userName & msg
  socket.emit("NEW_MESSAGE", { userName: name, msg });

Here’s the UI part for the button-

  onClick={() => handleSubmit(value)}
   <FontAwesomeIcon icon={faPaperPlane} />


  • Whenever the user clicks on the button to send the message, the event NEW_MESSAGE will be triggered. It will contain an object with a username and message. This event NEW_MESSAGE is being listened to at the server.

The User Interface will look something like this-

User Interface

Open your Network Tab to see the sending and receiving of the messages. Here’s the screenshot for the same.

Network Tab

The entire source code is available at the Github repository. Feel free to clone and play around with the code!


I hoped the tutorial helped you understand the steps of building a chat application. For more such knowledge, visit Bacancy’s Tutorials Page and learn about different technologies. You will be glad to know that each of the tutorials consists of a github repository, so feel free to clone and play around with the code.

Full-stack developers are best to hire because they have front-end and back-end insight for designing a solution. They try to give the optimum solutions which work best for both client and server sides.

Bacancy has skilled and experienced Full-stack developers. Are you looking for a Full-stack developer? If yes, then contact us and hire Full-stack developer to meet your requirements.

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