Requesting in HTTP vs Requesting KoaJS

Node.js: Node.js is an open-source and cross-platform runtime environment for executing JavaScript code outside a browser. You need to remember that NodeJS is not a framework and it’s not a programming language. Most of the people are confused and understand it’s a framework or a programming language. We often use Node.js for building back-end services like APIs like Web App or Mobile App.

http Module

Import http module: Import http module and store returned HTTP instance into a variable.

Syntax:

var http = require("http");

Creating and Binding Server: Create a server instance using createServer() method and bind it to some port using listen() method.

Syntax:

const server = http.createServer().listen(port)

Parameter: This method (listen()) accepts a single parameter as mentioned above and described below:

• port <Number>: Ports are in the range 1024 to 65535 containing both registered and Dynamic ports.

Below example illustrate the use of http module in Node.js.

Example 1: Filename: index.js

// Node.js program to create
// http server

// Using require to access http module
const http = require("http");

// Port number
const PORT = process.env.PORT || 2020;

// Creating server
const server = http.createServer(
  // Server listening on port 2020
  function (req, res) {
     // Write a response to the client
     res.write('Hello geeksforgeeks!');
     res.end();
  }
)
.listen(PORT, error => {
 // Prints in console
 console.log(`Server listening on port ${PORT}`)
 });

Run index.js file using the following command:

node index.js

Output:

Server listening on port 2020

Now type http://127.0.0.1:2020/ OR http://localhost:2020 in a web browser to see the output.

Koa Module

In order to use the Koa module, we need to install the NPM (Node Package Manager) and the following modules (on cmd).

>> npm init // Creates package.json file
>> npm install koa --save //  Installs express module
>> npm i koa -s // OR 

Import KoaJS module: Import KoaJS module and store returned instance into a variable.

Syntax:

var koa = require("koa"); // Importing koa module

Creating Server: The above syntax imports the koa module and creates a new koa application which gets stored inside the app variable.

Syntax:

const app = new koa();  // Creating koa application

Sending and listening to the response: It communicates the request and response with the client and the server. It requires PORT <number> and IP <number> to communicate.

app.listen(PORT, IP, Callback);

Parameter: This method accepts three parameters as mentioned above and described below:

• PORT <Number>: Ports are the endpoints of communication which helps to communicate with the client and the server.

• IP <Number>: IPs represent IPv4 or IPv6 address of a host or a device.

• Callback <Function>: It accepts a function.

The below example illustrates the KoaJS module in Node.js.

Example 2: Filename: index.js

// Node.js program to create server
// with help of Koa module

// Importing koa
const koa = require('koa');

// Creating new koa app
const app = new koa();

// PORT configuration
const PORT = process.env.PORT || 2020;

// IP configuration
const IP = process.env.IP || 2021;

app.use(function *() {
 this.body = "Hello GeeksForGeeks!";
});

// Server listening to requests
app.listen(PORT, IP, ()=>{
console.log("Server started at port", PORT);
});

Run index.js file using the following command:

node index.js

Output:

The Server is running at port 2020

Now type http://127.0.0.1:2020/ OR http://localhost:2020/ in a web browser to see the output.