Initial Version

Create a package

Run the npm init command to create a package.json file for your application.

npm init

This command prompts you for a number of things, such as the name and version of your application. For now, you can simply hit RETURN to accept the defaults for most of them except the entry point.

We prefer to use app.js rather than index.js.

Its result should be similar to this:

package name: (lr_webchat_node) 
version: (1.0.0) 
description: Chat app back-end built in node.js.
entry point: (index.js) app.js
test command: 
git repository: https://github.com/Literank/lr_webchat_node.git
keywords: socket.io,websocket
author: literank.com
license: (ISC) MIT
About to write to /Users/netdong/workspace/2023/projects/lr_webchat_node/package.json:

{
  "name": "lr_webchat_node",
  "version": "1.0.0",
  "description": "Chat app back-end built in node.js.",
  "main": "app.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "repository": {
    "type": "git",
    "url": "git+https://github.com/Literank/lr_webchat_node.git"
  },
  "keywords": [
    "socket.io",
    "websocket"
  ],
  "author": "literank.com",
  "license": "MIT",
  "bugs": {
    "url": "https://github.com/Literank/lr_webchat_node/issues"
  },
  "homepage": "https://github.com/Literank/lr_webchat_node#readme"
}

This command creates a package.json file in which dependencies you add will be listed for tracking.

Install Dependencies

Install Socket.IO:

npm i socket.io

This command updates the package.json file and creates a package-lock.json file in your project.

Module Type

Update package.json:

@@ -1,6 +1,7 @@
 {
   "name": "lr_webchat_node",
   "version": "1.0.0",
+  "type": "module",
   "description": "Chat app back-end built in node.js.",
   "main": "app.js",
   "scripts": {

In a package.json file, "type": "module" indicates that the project is using ECMAScript modules (ES modules) rather than CommonJS modules.

Integrating Socket.IO

Create app.js:

import { createServer } from "http";
import { Server } from "socket.io";

// Create a basic HTTP server
const server = createServer();
// Attach Socket.IO to the HTTP server with CORS enabled
const io = new Server(server, {
  cors: {
    origin: "*", // Access from any origin
  },
});

// Handle incoming socket connections
io.on("connection", (socket) => {
  console.log("A user connected", socket.id);
});

// Start the server
const PORT = process.env.PORT || 4000;
server.listen(PORT, () => {
  console.log("Chat Server listening on port " + PORT);
});

Run the program like this:

node app.js

You will get one line like this:

Chat Server listening on port 4000

Your chat server is running on port 4000 now.

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