There is one module we need to use for creating node.js first sample application. which can receive the client's request and respond according to it.

Creating Node.js Application

Step 1 - Import Required Module

We use the require directive to load the http module and store the returned HTTP instance into an http variable as follows −

var http = require("http");

Step 2 - Create a Server

We use the created http instance and call http.createServer() method to create a server instance and then we bind it at port 3000 using the listen method associated with the server instance. Pass it a function with parameters request and response. Write the sample implementation to always return "Welcome to node app".

const http = require("http");

const handler = (req, res) => {
    // Send the HTTP header 
    // HTTP Status: 200 : OK
    // Content Type: text/plain
    res.writeHead(200, { "content-type": "text/plain" });

    // Send the response body as "Welcome to node app"
    res.end("Welcome to node app");
}

const server = http.createServer(handler);
server.listen(3000, () => {
    // Console will print the message
    console.log("Server Started on port 3000");
});

The above code is enough to create an HTTP server that listens, i.e., waits for a request over 3000 port on the local machine.

Step 3 - Testing Request & Response

Let's put steps 1 and 2 together in a file called index.js and start our HTTP server as shown below −

Now execute the index.js to start the server as follows −

$ node index.js

Verify the Output. The server has started.

Server running at http://127.0.0.1:3000/ or http://localhost:3000/