Building a Server

1. Create a server folder #

2. Create server.js file #

• server .js

// To use the server, store the http module in the http variable
let http = require('http');

// Create a server using the http module
// Writing it as below creates a server, and when an http request comes from a user, it executes the code inside the function block to respond.
let server = http.createServer(function(request,response){
  response.writeHead(200, {'Content=Type':'text/html'});
  response.end('Hello node.js!');
});

// 3. Run the server with port 8080 using the listen function.
server.listen(8000, function(){
  console.log('Server is running...');
});

Running and Accessing server.js #

Terminal

$ node server

After running, if "Hello node.js!" appears correctly on http://localhost:8080, it's a success.

Code Analysis #

let http = require('http');

To run a web server, we load the http module using require. (require has a similar function to import.) After require, Node.js stores the module in an http variable and uses it as an independent object.

The server is created using the createServer function defined in the http module. A typical function is used like this:

function nameOfFunction(parameter){
  // execution logic
}

The function(request, response){} passed as a parameter to createServer() does not have a name.

A parameter written simply as function without a name becomes a callback when an event occurs. That is, when a request comes to the created server, the logic inside the function is executed, passing values that can be used under the names request and response declared within the function. Therefore, any values passed as request and response can be used inside the function block {}.

let server.createServer(function(request,response){
  response.writeHead(200,{'Content-Type':'text/html'});
  response.end('Hello node.js!');
})

In the code below, the response object is used to return a value to the client. First, in the writeHead() function:

The first value is the number 200,

The second value is in the form of { 'key' : 'value' } inside the {} curly braces.

response.writeHead(200,{'Content-Type':'text/html'});

The first number, 200, is an HTTP status code used when a web server successfully returns a value for an incoming request. If the server processes the request normally without errors, it sets the response header with a 200 code.

The second value, {'Content-Type':'text/html'}, defines that the content type sent from the server is text and in HTML format.