Backend communication refers to how the backend (server-side) of an application interacts with other systems, services, or databases to perform operations, process data, or respond to client (frontend) requests

Types of communication

Synchronous (Strong coupling)

1. HTTP (REST/GraphQL)

2. Websocket (debatable if sync or async)

Asynchronous (Weak coupling)

1. Messaging queues

2. Pub subs

3. Server-Sent Events

4. Websocket (debatable if sync or async)

Websockets

WebSockets provide a way to establish a persistent, full-duplex communication channel over a single TCP connection between the client (typically a web browser) and the server.

Use Cases for WebSockets:

• Real-Time Applications: Chat applications, live sports updates, real-time gaming, and any application requiring instant updates can benefit from WebSockets.

• Live Feeds: Financial tickers, news feeds, and social media updates are examples where WebSockets can be used to push live data to users.

• Interactive Services: Collaborative editing tools, live customer support chat, and interactive webinars can use WebSockets to enhance user interactio

Good example - https://www.binance.com/en/trade/SOL_USDT?type=spot

Why not use HTTP/REST? Why do you need ws?

Limitations of HTTP/REST:

1. One-way communication

   • The client (browser/app) makes a request. The server can only respond—it can’t initiate communication.

2. No real-time updates

   • For things like chat, live notifications, or stock prices, you’d need to constantly poll the server (send repeated requests), which is inefficient.

3. Stateless

   • Each request is independent; the server doesn't remember previous interactions without extra effort (e.g., sessions or tokens).

Why Use WebSockets (ws)?

• Real-time communication

  • Perfect for apps like chat, multiplayer games, live dashboards, collaborative editors (like Google Docs), etc.

• Low latency, efficient

  • No need for constant HTTP requests; once connected, data flows instantly as needed.

• Two-way interaction

  • The server can send data anytime, without waiting for the client to ask.

Websockets in Node.js

There are various libraries that let you create a ws server (similar to how express lets you create an HTTP server)

1. https://www.npmjs.com/package/websocket

2. https://github.com/websockets/ws

3. https://socket.io/

Create websocket server:

• Initialize an empty Node.js project

npm init -y

• Add tsconfig to it

npx tsc --init
npm install typescript

• Update tsconfig

"rootDir": "./src",
"outDir": "./dist",

Create folders src and create file inside it i.e index.ts

• change in package.json

"scripts":
{
"dev": "tsc -b && node ./dist/index.js"
},

now your all ts file will save in src folder and js file will save in dist folder.

• Install ws

npm i ws @types/ws

index.ts:

import { WebSocketServer } from 'ws';

const wss = new WebSocketServer({ port: 8080 });

//event handler
wss.on('connection', function connection(socket) {

    console.log("user connected")
    socket.send('Hello');

    setInterval(() => {
        socket.send("current price is :" + Math.random());
    },500)

    socket.on("message", (e) =>{
    console.log(e.toString())
    })

});

enter all code. run program in terminal with npm run dev command.

open postman (client)

server to client postman -> websocket -> url:ws://localhost:8080 -> send

client to server postman -> connect url -> type message-> send it. -> it will print on vs code.