DEV Community

Cover image for How to build a real-time Auction System with Socket.io and React.js 🀯
Nevo David for novu

Posted on • Originally published at novu.co

How to build a real-time Auction System with Socket.io and React.js 🀯

What is this article about?

Like an actual auction, if you bid for a product, you get counterbids from other bidders. The auction runs on the "fast" decision bid, where somebody else will win or outbid you if you don't bid fast enough.

To use online bidding, We must stick to the same principles. We must give our bidder information as soon as a new bid comes.

Auction

There are two ways to get live information from your server about a new bid:

  1. Use long-polling HTTP request, basically an HTTP request every 5 - 10 seconds to get information about a new bid.

  2. Use an open-socket (Websockets) to get information directly from the server when a new bid arrives.

In this article I will talk about Websockets and specifically on the Node.js library - Socket.io

Novu - the first open-source notification architecture

Just a quick background about us. Novu is the first open-source notification infrastructure. We basically help to manage all the product notifications. It can be In-App (the bell icon like you have in Facebook), Emails, SMSs and so on.

Looking for new contributors

Come help us out to build the best open-source notification infrastructure, get recognized by the community, and become a Community Hero here:
https://novu.co/contributors

Community Heroes

So what the hack is Socket.io?

Socket.ioΒ is a JavaScript library that enables us to create real-time, bi-directional communication between web browsers and a Node.js server. It is a highly performant library capable of processing a large volume of data within the shortest possible time.

Usually, to get information from the server you need send an HTTP request. With websockets, the server lets you know when there is new information without asking it.

In this article, we'll leverage the real-time communication provided by Socket.io to create a bidding system that allows users to put items up for auction and bid for them. Socket.io will also notify users when an item is up for auction and after a user places a bid.

How to add Socket.io to React & Node.js applications

In this section, we'll set up the project environment for our bidding system. You'll also learn how to add Socket.io to a React and Node.js application and connect both development servers for real-time communication via Socket.io.

Create the project folder containing two sub-folders named client and server.

mkdir bidding-system
cd bidding-system
mkdir client server
Enter fullscreen mode Exit fullscreen mode

Navigate into the client folder via your terminal and create a new React.js project.

cd client
npx create-react-app ./
Enter fullscreen mode Exit fullscreen mode

Install Socket.io client API and React Router.Β React RouterΒ is a JavaScript library that enables us to navigate between pages in a React application.

npm install socket.io-client react-router-dom
Enter fullscreen mode Exit fullscreen mode

Delete the redundant files such as the logo and the test files from the React app, and update the App.js file to display Hello World as below.

function App() {
  return (
    <div>
      <p>Hello World!</p>
    </div>
  );
}
Enter fullscreen mode Exit fullscreen mode

Next, navigate into the server folder and create a package.json file.

cd server
npm init -y
Enter fullscreen mode Exit fullscreen mode

Install Express.js, CORS, Nodemon, and Socket.io Server API.

Express.js is a fast, minimalist framework that provides several features for building web applications in Node.js.Β CORS is a Node.js package that allows communication between different domains.

Nodemon is a Node.js tool that automatically restarts the server after detecting file changes, andΒ Socket.io allows us to configure a real-time connection on the server.

Β 

npm install express cors nodemon socket.io 
Enter fullscreen mode Exit fullscreen mode

Create an index.js file - the entry point to the web server.

touch index.js
Enter fullscreen mode Exit fullscreen mode

Set up a simple Node.js server using Express.js. The code snippet below returns a JSON object when you visit the http://localhost:4000/api in your browser.

//index.js
const express = require('express');
const app = express();
const PORT = 4000;

app.get('/api', (req, res) => {
  res.json({
    message: 'Hello world',
  });
});

app.listen(PORT, () => {
  console.log(`Server listening on ${PORT}`);
});
Enter fullscreen mode Exit fullscreen mode

Import the HTTP and the CORS library to allow data transfer between the client and the server domains.

const express = require('express');
const app = express();
const PORT = 4000;

//New imports
const http = require('http').Server(app);
const cors = require('cors');

app.use(cors());

app.get('/api', (req, res) => {
  res.json({
    message: 'Hello world',
  });
});

http.listen(PORT, () => {
  console.log(`Server listening on ${PORT}`);
});
Enter fullscreen mode Exit fullscreen mode

Next, add Socket.io to the project to create a real-time connection. Before the app.get() block, copy the code below.

//New imports
.....
const socketIO = require('socket.io')(http, {
    cors: {
        origin: "http://localhost:3000"
    }
});

//Add this before the app.get() block
socketIO.on('connection', (socket) => {
    console.log(`⚑: ${socket.id} user just connected!`);
    socket.on('disconnect', () => {
      console.log('πŸ”₯: A user disconnected');
    });
});
Enter fullscreen mode Exit fullscreen mode

From the code snippet above, the socket.io("connection") function establishes a connection with the React app, then creates a unique ID for each socket and logs the ID to the console whenever a user visits the web page.

When you refresh or close the web page, the socket fires the disconnect event showing that a user has disconnected from the socket.

Next, configure Nodemon by adding the start command to the list of the scripts in the package.json file. The code snippet below starts the server using Nodemon.

//In server/package.json

"scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "nodemon index.js"
  },
Enter fullscreen mode Exit fullscreen mode

You can now run the server with Nodemon by using the command below.

npm start
Enter fullscreen mode Exit fullscreen mode

Open the App.js file in the client folder and connect the React app to the Socket.io server.

import socketIO from 'socket.io-client';
const socket = socketIO.connect('http://localhost:4000');

function App() {
  return (
    <div>
      <p>Hello World!</p>
    </div>
  );
}
Enter fullscreen mode Exit fullscreen mode

Start the React.js server.

npm start
Enter fullscreen mode Exit fullscreen mode

Check the terminal where the server is running; the ID of the React.js client appears in the terminal.

Congratulations πŸ₯‚ , the React app has been successfully connected to the server via Socket.io.

πŸ’‘ For the remaining part of this article, I will walk you through creating the flow of the bidding system, and in the upcoming article in this series, I will guide you through sending messages between the client and the server and saving them in a JSON file.

πŸ’‘ The JSON file will serve as the database for the application. Although this is not a secure way of saving data, this is just a demo, so feel free to use any database of your choice if necessary.

The Workflow for the Bidding System

Before we start building each component, I'll walk you through the application's workflow.

Here is how it works:

  • The Home page: Users provide only their username, and the application saves this username for identification throughout the application. To keep the tutorial simple, we won't use any authentication library.
  • The Products page: Users can view all the products up for auction, click on each product to bid, and there is a call to action that redirects users to the page where they can add items for auction.
  • The Add Products page: This page allows users to add the name and price of the auction item, then redirects them to the Products page to view the recently added item.
  • The Bid page: Users can bid for the item they selected from the Products page. This page accepts URL parameters containing the name and the price of the chosen item; then displays a form input that allows users to bid up the product.
  • The Nav component: All the pages have the Nav component at the top and display notifications within it. When a user sets a bid or adds a new product, the Nav component notifies every other user.

Nav

Without any further ado, create a component folder containing all the pages. Ensure that each page renders an HTML element.

cd src
mkdir components
cd components
touch Home.js Products.js AddProduct.js BidProduct.js Nav.js
Enter fullscreen mode Exit fullscreen mode

Next, Import all the files within the components folder into the App.js file and create a route for each page usingΒ React Router v6.

//Pages import
import Home from './components/Home';
import AddProduct from './components/AddProduct';
import BidProduct from './components/BidProduct';
import Products from './components/Products';
import Nav from './components/Nav';
import socketIO from 'socket.io-client';
import { Route, Routes, BrowserRouter as Router } from 'react-router-dom';

const socket = socketIO.connect('http://localhost:4000');

function App() {
  return (
    <Router>
      <div>
        {/* Nav is available at the top of all the pages as a navigation bar */}
        <Nav socket={socket} />
        <Routes>
          <Route path="/" element={<Home />} />
          <Route path="/products" element={<Products />} />
          <Route
            path="/products/add"
            element={<AddProduct socket={socket} />}
          />
          {/* Uses dynamic routing */}
          <Route
            path="/products/bid/:name/:price"
            element={<BidProduct socket={socket} />}
          />
        </Routes>
      </div>
    </Router>
  );
}

export default App;
Enter fullscreen mode Exit fullscreen mode

The code snippet declares the route for each page and passes the Socket.io library into the necessary components.

Navigate into the src/index.css and copy the code below. It contains all the CSS required for styling this project.

/* --------General Stylesheet for the project ------*/
@import url('https://fonts.googleapis.com/css2?family=Poppins:wght@100;200;300;400;500;600;700;800;900&display=swap');
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: 'Poppins', sans-serif;
}
body {
  margin: 0;
}

/* --------Stylesheet for the Navigation component ------*/
.navbar {
  width: 100%;
  height: 10vh;
  background-color: #f0ebe3;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 20px;
  margin-bottom: 30px;
}
.navbar .header {
  width: 70%;
}

/* --------Stylesheet for the Home component ------*/
.home__form {
  width: 100%;
  height: 80vh;
  padding: 20px;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-direction: column;
}
.home__input,
.addProduct__form input,
.bidProduct__form input {
  width: 70%;
  padding: 10px;
  border-radius: 5px;
  margin: 15px 0;
  outline: none;
  border: 1px solid #576f72;
}
.home__cta {
  width: 200px;
  padding: 10px;
  font-size: 16px;
  outline: none;
  border: none;
  cursor: pointer;
  color: #fff;
  background-color: rgb(67, 143, 67);
}

/* --------Stylesheet for the Products component ------*/
.editIcon {
  height: 20px;
  cursor: pointer;
}
table {
  width: 95%;
  border: 1px solid #576f72;
  margin: 0 auto;
  border-collapse: collapse;
}
tr,
td,
th {
  border: 1px solid #576f72;
  text-align: center;
  padding: 5px;
}
.table__container {
  display: flex;
  align-items: center;
  flex-direction: column;
}
.products__cta {
  width: 70%;
  background-color: rgb(67, 143, 67);
  padding: 15px;
  color: #fff;
  margin-bottom: 35px;
  border-radius: 5px;
  text-decoration: none;
  text-align: center;
}

/* --------Stylesheet for the AddProducts & BidProducts component ------*/
.addproduct__container,
.bidproduct__container {
  width: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
}
.addproduct__container h2,
.bidproduct__container h2 {
  margin-bottom: 30px;
}
.addProduct__form,
.bidProduct__form {
  display: flex;
  flex-direction: column;
  width: 80%;
  margin: 0 auto;
}
.addProduct__cta,
.bidProduct__cta {
  width: 200px;
  padding: 10px;
  font-size: 16px;
  outline: none;
  border: none;
  color: #fff;
  background-color: rgb(67, 143, 67);
  cursor: pointer;
}
.bidProduct__name {
  margin-bottom: 20px;
}
Enter fullscreen mode Exit fullscreen mode

Congratulations πŸ’ƒπŸ», we can start coding every part of the project.

Creating the Home page of the application

In this section, we'll create the home page for the bidding system. The page will accept the username from the user and then save it to the local storage for identification throughout the application.

Update the Home.js file to render a form field that accepts a minimum of six letters as username.

import React, { useState } from 'react';

const Home = () => {
  const [userName, setUserName] = useState('');

  return (
    <div>
      <form className="home__form" onSubmit={handleSubmit}>
        <label htmlFor="username">Enter your username</label>
        <input
          type="text"
          name="username"
          className="home__input"
          value={userName}
          onChange={(e) => setUserName(e.target.value)}
          required
          minLength={6}
        />
        <button className="home__cta">SIGN IN</button>
      </form>
    </div>
  );
};

export default Home;
Enter fullscreen mode Exit fullscreen mode

Create the handleSubmit function that stores the username in the local storage, then redirects the user to the Products page after submitting the form.

From the code snippet below, the useNavigate hook enables us to redirect users between pages.

import React, { useState } from 'react';
import { useNavigate } from 'react-router-dom';

const Home = () => {
  const [userName, setUserName] = useState('');
  const navigate = useNavigate();

  const handleSubmit = (e) => {
    e.preventDefault();
    localStorage.setItem('userName', userName);
    navigate('/products');
  };

  return <div>.....</div>;
};

export default Home;
Enter fullscreen mode Exit fullscreen mode

Creating the Products page

In this section, I'll walk you through creating a simple layout that displays each product and the related information. The product details include the name, price, owner, and the last bidder.
A table layout containing each product on every row is the least complicated layout for this data structure.
So, let's code it! πŸ’ͺ

Products Page

Update the Products.js to display a table containing two products with four columns containing the name, price, last bidder, and the creator.

import React from 'react';
const Products = () => {
  return (
    <div>
      <div className="table__container">
        <table>
          <thead>
            <tr>
              <th>Name</th>
              <th>Price</th>
              <th>Last Bidder</th>
              <th>Creator</th>
            </tr>
          </thead>
          {/* Data for display, we will later get it from the server */}
          <tbody>
            <tr>
              <td>Tesla Model S</td>
              <td>$30,000</td>
              <td>@david_show</td>
              <td>@elon_musk</td>
            </tr>

            <tr>
              <td>Ferrari 2021</td>
              <td>$50,000</td>
              <td>@bryan_scofield</td>
              <td>@david_asaolu</td>
            </tr>
          </tbody>
        </table>
      </div>
    </div>
  );
};

export default Products;
Enter fullscreen mode Exit fullscreen mode

We've been able to display the items available for auction to the users. Next, we need to allow users to add a product and bid on each item. An easy way is to create a hyperlink that links to the Add Products page and an edit button for bidding on items.

Update the Products page to contain the edit button and a call to action for adding products.

import React from 'react';
import { Link } from 'react-router-dom';

const Products = () => {
  return (
    <div>
      <div className="table__container">
        <Link to="/products/add" className="products__cta">
          ADD PRODUCTS
        </Link>

        <table>
          <thead>
            <tr>
              <th>Name</th>
              <th>Price</th>
              <th>Last Bidder</th>
              <th>Creator</th>
              <th>Edit</th>
            </tr>
          </thead>
          {/* Data for display, we will later get it from the server */}
          <tbody>
            <tr>
              <td>Tesla Model S</td>
              <td>$30,000</td>
              <td>@david_show</td>
              <td>@elon_musk</td>
              <td>
                <button>Edit</button>
              </td>
            </tr>

            <tr>
              <td>Ferrari 2021</td>
              <td>$50,000</td>
              <td>@bryan_scofield</td>
              <td>@david_asaolu</td>
              <td>
                <button>Edit</button>
              </td>
            </tr>
          </tbody>
        </table>
      </div>
    </div>
  );
};

export default Products;
Enter fullscreen mode Exit fullscreen mode

Creating the Add Product page

In this section, we'll create the AddProduct page containing a form with two input fields for the name and price of the product up for auction and a submit button.

Product Page

import React, { useState } from 'react';
import { useNavigate } from 'react-router-dom';

const AddProduct = () => {
  const [name, setName] = useState('');
  const [price, setPrice] = useState(0);
  const navigate = useNavigate();

  const handleSubmit = (e) => {
    e.preventDefault();
    console.log({ name, price, owner: localStorage.getItem('userName') });
    navigate('/products');
  };

  return (
    <div>
      <div className="addproduct__container">
        <h2>Add a new product</h2>
        <form className="addProduct__form" onSubmit={handleSubmit}>
          <label htmlFor="name">Name of the product</label>
          <input
            type="text"
            name="name"
            value={name}
            onChange={(e) => setName(e.target.value)}
            required
          />

          <label htmlFor="price">Starting price</label>
          <input
            type="number"
            name="price"
            value={price}
            onChange={(e) => setPrice(e.target.value)}
            required
          />

          <button className="addProduct__cta">SEND</button>
        </form>
      </div>
    </div>
  );
};

export default AddProduct;
Enter fullscreen mode Exit fullscreen mode

From the code above, the handleSubmit button collects the user's input from the form and logs it to the console before redirecting to the Products page. The username saved to the local storage is also attached to the item as the product owner.

Creating the Bid page

The Bid page is quite similar to the AddProduct page. It contains a form with an input field for the bid price of the selected product and a call to action. After a user places a bid, it redirects them to the Product page.

import React, { useState } from 'react';
import { useNavigate } from 'react-router-dom';

const BidProduct = () => {
  const [userInput, setUserInput] = useState(0);
  const navigate = useNavigate();

  const handleSubmit = (e) => {
    e.preventDefault();
    navigate('/products');
  };

  return (
    <div>
      <div className="bidproduct__container">
        <h2>Place a Bid</h2>
        <form className="bidProduct__form" onSubmit={handleSubmit}>
          <h3 className="bidProduct__name">Product Name</h3>

          <label htmlFor="amount">Bidding Amount</label>
          <input
            type="number"
            name="amount"
            value={userInput}
            onChange={(e) => setUserInput(e.target.value)}
            required
          />

          <button className="bidProduct__cta">SEND</button>
        </form>
      </div>
    </div>
  );
};

export default BidProduct;
Enter fullscreen mode Exit fullscreen mode

Creating the Nav component

The Nav component is at the top of every page (according to the App.js file). It represents the app's notification center - where users view the notifications from Socket.io.

Update the Nav.js file to render a <nav> element as below. The h2 element represents the logo, and the notification container is on the right-hand side of the screen.

import React from 'react';

const Nav = () => {
  return (
    <nav className="navbar">
      <div className="header">
        <h2>Bid Items</h2>
      </div>

      <div>
        <p style={{ color: 'red' }}>My notifications are here</p>
      </div>
    </nav>
  );
};

export default Nav;
Enter fullscreen mode Exit fullscreen mode

Congratulations, we've completed the first part of this series. Next week article in this series, I'll walk you through sending messages between the React app and the Node.js server.

You can find the full-source code here:
https://github.com/novuhq/blog/tree/main/bidding%20system%20using%20socketIO

Make sure you follow me to get a notification once I release the next part of the series!
https://dev.to/nevodavid

Nevo David

Thank you for reading! πŸ₯‚

Discussion (17)

Collapse
nevodavid profile image
Nevo David Author

Have you seen Novu community heroes project?
novu.co/contributors

Collapse
joelbonetr profile image
JoelBonetR • Edited on

I don't know if you can do something about that neither if it counts as contribution but novu.co needs a css rule:

a { 
  word-break: break-all;
}
Enter fullscreen mode Exit fullscreen mode

As the GitHub link on the original post breaks the responsive πŸ˜…πŸ˜

I find this notifications project very useful and I may take a look as soon as I come back from vacations. Is there any contributors "getting started" ruleset or whatever?

Thank you!

Edit: just saw the guide to become a contributor in the hero page linked :)

Collapse
nevodavid profile image
Nevo David Author

You can join our Discord in the meanwhile :D
discord.novu.co

Thread Thread
joelbonetr profile image
JoelBonetR

Expired invit. πŸ˜•

Thread Thread
nevodavid profile image
Nevo David Author

🀯
Try now

Thread Thread
joelbonetr profile image
JoelBonetR

Done! From the hero page's permanent invit (at the footer) btw, if you pick invitations manually it will generate a new link each time instead 😁

Collapse
nevodavid profile image
Nevo David Author

The second part is here!
dev.to/novu/how-to-build-a-real-ti...

Collapse
nevodavid profile image
Nevo David Author

I am looking to write some new websockets articles, what should I write about?

Collapse
yongchanghe profile image
Yongchang He

Thank you for sharing!

Collapse
nevodavid profile image
Nevo David Author

You are welcome!

Collapse
obaino82 profile image
Obaino82

Nice oneπŸ’―

Collapse
nevodavid profile image
Nevo David Author

Thank you, Obaino82!
Have you used Websockets before?

Collapse
nevodavid profile image
Nevo David Author

Have you ever used websockets before?

Collapse
joelbonetr profile image
JoelBonetR

Yes, to build a real time chat app with rooms in Node JS and React. It was meant to be integrated on a current software and went well. Pretty easy and straightforward if I must πŸ™‚

Collapse
nevodavid profile image
Nevo David Author

Where can I see it? :)

Thread Thread
joelbonetr profile image
JoelBonetR

It was a private repo for a client but there's no much secret around that, If you're interested into collabing we may code a new one and then write a post to wrap it up.

It could well be a "weekend project"

Collapse
mela profile image
Kutte

Thank you for sharing!