This document provides a comprehensive tutorial on building a chat application using React.js, Node.js, and Socket.io, outlining both server-side and client-side implementation. It covers the necessary dependencies, technical concepts, and detailed code examples for establishing WebSocket connections, handling user messages, and creating a user-friendly interface. The tutorial concludes with encouragement to explore further and consider hiring full-stack developers for optimal solutions.

1. How to Build a
Chat
application
with ReactJS,
NodeJS, and
Socket.IO?
www.bacancytechnology.com

2. Introduction

3. 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.

4. What is
Socket.IO?

5. 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 socket.io libraries on
the client and server sides.
It’s impossible to corner socket.io 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:

6. Tutorial Goal:
What are we
building?

7. https://www.youtube.com/watch?
v=hNBmbjJ6ETo&t=1s

8. The Flow of
Building Chat
App

9. 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.
You have seen what we are building. Let’s
see a high-level overview of the
development flow.

10. 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.

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

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

13. Install Dependencies
npm i express socket.io 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);
server.listen(PORT);

14. Socket.IO Connection
It’s time to add socket.io 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
socket.io.
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) => {

15. // Joining room for conversation
socket.on("JOIN_ROOM", (room) => {
roomId = room;
socket.join(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) => {
io.to(roomId).emit("NEW_MESSAGE", msg);
});
// To disconnect participant from room
// And remove specific user from object
socket.on("disconnect", () => {
activeUsers.delete(socket.userId);
// Triggering this event disconnects user
io.to(roomId).emit("user disconnected", socket.userId);
});
});

16. Explanation
When a user sends a message in the
room, we want all the users to receive
that message.
We will import socket.io 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 socket.io, 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.

17. 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.

18. Client-Side
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 socket.io-client

19. 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 "socket.io-client";
// socketIOClient connects front-end to with
socket backend URL
export const socket =
socketIOClient(process.env.REACT_APP_SOCK
ET_URL, {
transports: [ "websocket" ],
reconnectionAttempts: 20,
reconnectionDelay: 5000
});

20. 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-

21. 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.

22. const handleOnJoinRoom = () => {
if (roomId.trim().length > 0) {
auth.login();
setItemInStorage('user', {
name: userName,
});
history.push(`/${roomId}`);
}
};
const onLoginClick = (e) => {
e.preventDefault();
if (roomType ===
ROOM_TYPE.createRoom) {
setLoading(true);
toastSuccess('Room created!!');
getCreateRoom()
.then((res) => {
setLoading(false);
if (res && res.roomUrl) {
auth.login();

23. setItemInStorage('user', {
name: userName,
});
history.push(`/${res.roomUrl}`);
}
})
.catch((err) => {
setLoading(false);
toastError(err);
});
} else {
handleOnJoinRoom();
}
};
Once the user is logged in, they are
redirected to the Dashboard.
The UI for Dashboard will be something like
this-

24. 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';

25. 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 />
</div>
</Container>
</Container>
</>
);
};
export default DashBoard;

26. Explanation
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.

27. 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
? messages.map((message, index) => (
<div
className={`msg-container msg-
container-${
message.userName === name ? 'right' :
'left'

28. }`}
key={index}
>
<div className="msg-header">
<span className="msg-user-name">
{message.userName}
</span>
</div>
<div className="msg-content">
<span className="msg-text">
{message.msg}
</span>
</div>
</div>
))
: null}
<div style={{ float: 'left', clear: 'both' }} ref=
{messagesEnd} />
</>
);
};
ChatContainer.propTypes = {
messages: PropTypes.array.isRequired,
};
export default ChatContainer;

29. 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) => {
setValue("");
// Trigger NEW_MESSAGE with object
containing userName & msg
socket.emit("NEW_MESSAGE", { userName:
name, msg });
};

30. Here’s the UI part for the button-
<Button
className="ml-2"
color="primary"
disabled={!value.trim().length}
onClick={() => handleSubmit(value)}
>
<FontAwesomeIcon icon={faPaperPlane}
/>
</Button>
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.
Explanation
The User Interface will look something like
this-

31. Open your Network Tab to see the sending
and receiving of the messages. Here’s the
screenshot for the same.
The entire source code is available at the Github
repository. Feel free to clone and play around
with the code!

32. Conclusion

33. 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.

34. Thank You
www.bacancytechnology.com