Build Your First HTTP Server in NodeJS

In this tutorial, we will be talking about how we can set up a simple NodeJS HTTP server with a beginner’s perspective. NodeJS is a fantastic candidate for creating web servers which are light weight and can handle a very good volume of requests.

NodeJS is shipped with several core modules out of which we will be using HTTP to set up our own HTTP server. HTTP module makes it dead simple to create an HTTP server via its simple but powerful API. Let’s create an empty file named `myFirstHTTPServer.js` and write the following code into it:
[cc lang=”javascript”]
//Lets require/import the HTTP module
var http = require(‘http’);

//Lets define a port we want to listen to
const PORT=8080;

//We need a function which handles requests and send response
function handleRequest(request, response){
response.end(‘It Works!! Path Hit: ‘ + request.url);
}

//Create a server
var server = http.createServer(handleRequest);

//Lets start our server
server.listen(PORT, function(){
//Callback triggered when server is successfully listening. Hurray!
console.log(“Server listening on: http://localhost:%s”, PORT);
});
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Now to see the NodeJS magic simply run the server by running the file. In the terminal you can following command to run your program:

“`bash
> node myFirstHTTPServer.js
#output
Server listening on: http://localhost:8080
“`
Hurray! now open up the URL http://localhost:8080 on your browser and it should serve you the text returned from our program. Play with the path of the URL and see the message displayed.

Analysis of the above program:
Now let’s break the above program into sub blocks and see what’s happening:

Loading HTTP module
NodeJS has core modules to create `http/https` servers, hence we have to import the `http` module in order to create an HTTP Server.
[cc lang = “javascript”]
//Lets require/import the HTTP module
var http = require(‘http’);
[/cc]

Defining the handler function
We need a function which will handle all requests and reply accordingly. This is the point of entry for your server application, you can reply to requests as per your business logic.

[cc lang = “javascript”]
//We need a function which handles requests and send response
function handleRequest(request, response){
response.end(‘It Works!! Path Hit: ‘ + request.url);
}

[/cc]

 Creating and starting the server

Here we are creating a new `HTTP Server Object` and then asking it to listen to on a `port`. The `createServer` method is used to create a new server instance and it takes our handler function as the argument. Then we call `listen` on the `server` object in order to start it.
[cc lang = “javascript”]
//Create a server
var server = http.createServer(handleRequest);

//Lets start our server
server.listen(PORT, function(){
//Callback triggered when server is successfully listening. Hurray!
console.log(“Server listening on: http://localhost:%s”, PORT);
});
[/cc]

Adding in a dispatcher
Now as we have a basic *HTTP Server* running, its time we implement some real functionalities. Your server should respond differently to different URL paths and hence we require a `dispatcher`. A dispatcher is kind of router which helps in calling the desired request handler code for each particular URL path.
Now lets add a dispatcher to our program. First we will install a `dispatcher` module. There are many modules available but lets install a basic one for demo purposes:
“`bash
> npm install httpdispatcher
“`
Now we will require the dispatcher in our program, add the following line on the top:
[cc lang = “javascript”]
var dispatcher = require(‘httpdispatcher’);
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Now lets use our dispatcher in our `handleRequest` function:

[cc lang = “javascript”]
//Lets use our dispatcher
function handleRequest(request, response){
try {
//log the request on console
console.log(request.url);
//Disptach
dispatcher.dispatch(request, response);
} catch(err) {
console.log(err);
}
}

/*
* Lets define some routes. You can move this in another file too.
*/
//For all your static(JS/CSS/Images/etc.) set the directory name(relative path).
dispatcher.setStatic(‘resources’);

//A sample GET request
dispatcher.onGet(“/page1”, function(req, res) {
res.writeHead(200, {‘Content-Type’: ‘text/plain’});
res.end(‘Page One’);
});
//A sample POST request
dispatcher.onPost(“/post1”, function(req, res) {
res.writeHead(200, {‘Content-Type’: ‘text/plain’});
res.end(‘Got Post Data’);
});
[/cc]
Now lets run the above program and try the following URL paths:

“`
GET /page1 => ‘Page One’
POST /page2 => ‘Page Two’
GET /page3 => 404
GET /resources/images-that-exists.png => Image resource
GET /resources/images-that-does-not-exists.png => 404
“`

All Done!! now you have a small simple `HTTP Server` running.

[cc lang = “html”]
body{
margin: 200px;
margin-top: 50px;
background: #fff;
padding: 40px;
border: 2px solid black;
border-radius: 30px;
height: 3650px;
}
html{
background: #eee;
}

[/cc]


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