Node.js HTTP Module

In node.js, HTTP module is a core module and it is useful to transfer the data over HTTP (hyper text protocol transfer).

 

Generally, in node.js we can include or import a modules by using require directive with module name so to include HTTP module, we need to use require() function like as shown below.

 

// importing node.js built-in http module

var http = require('http');

Node.js Create Web / HTTP Server

In node.js, by using HTTP module we can create HTTP server that listens on particular port and send the response back to the client.

 

Once, we import an http module by using require directive, our node.js application is having an access to HTTP module so we can create a web server using createServer() method to listen a request and response on particular port number like as shown below.

 

// import node.js built-in http module

var http = require('http');

// creating server

http.createServer(function (req, res) {

// Write response to client

res.write('Hello World!');

// End the response

res.end();

}).listen(4200); // Server object listen on port 4200

If you observe above code, we imported an http module by using require directive to access an HTTP module and created a HTTP server using createServer() method to listen the request (req) and response (res) on port number 4200.

 

Here, the function in http.createServer() method will be executed when someone tries to access our computer on port 4200.

 

Save the above code in a file called “Helloworld.js” and initiate it by entering a command like as shown following in node.js command prompt.

 

Initiate Http Module in Node.js Command Prompt

 

Now your computer will work as server so if anyone tries to access your computer with port 4200, then in return they will get a “Hello world” message like as shown below.

 

Node.js http module example result

 

This is how we can create a web server using HTTP module to manage the requests and responses by listening on particular port and send the response back to the client. 

Node.js Add HTTP Header

In node.js, HTTP header is useful to define a type of response i.e. either plain text, HTML or JSON, etc. based on our requirements. In node.js, by using either writeHead() or setHeader() methods, we can set the server response type.

 

If you observe above example, we didn’t mentioned any HTTP header type so the server will return the response as plain text even if it contain any HTML markups. In case, if you want the response from HTTP server as HTML, then we need to include HTTP header with the content type as text/html like as shown below.

 

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

 

//or

 

response.setHeader('content-type','text/html');

response.setHeader(200);

If you observe above statements, we defined a writeHead() and setHeader() methods with response status code (200) and return type (text/html). In node.js, writeHead() and setHeader() methods will do the same job but only difference is setHeader() will allow us to set singular header at a time and writeHead() will allow us to set multiple headers.

Node.js Add HTTP Header Example

Following is the example of adding an HTTP header to return the response type as HTML in node.js.

 

var http = require('http');

http.createServer(function (req, res) {

// response header to display content as html    

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

// Write response to client

res.write('<b>Hi Guest</b><br/>');

res.write('<span style="font-weight:bold; color:Green">Welcome to Tutlane</span>');

res.end();

}).listen(4200, console.info("Server listening on port 4200"));

Save the above code in a file called “serverhead.js” and initiate it by entering a command like as shown following in node.js command prompt.

 

Initiate Http Module with Http Header in Node.js Command Prompt

 

Now your computer will work as server so if anyone tries to access your computer with port 4200, then in return they will get a response in html format like as shown below.

 

Node.js Http Module with Http Header Example Result

 

If you observe example, the node.js HTTP server has returned the response in html format after adding the HTTP header.

Node.js HTTP Server Request

In above examples, while creating the HTTP server we are passing a function with request (req) and response (res) arguments. The request (req) argument in function is useful to handle the requests from client and it’s having a different properties like query string, body, events, etc.

 

Following is the example of reading the query string parameters using HTTP server request properties in node.js.

 

var http = require('http');

http.createServer(function (req, res) {

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

res.write(req.url);

res.end();

}).listen(4200, console.info("Server listening on port 4200"));

If you observe above example, we are trying to read the query string parameter details using request object property called “url”. The url property is useful to read the part of url that comes after the domain name.

 

Save the above code in a file called “httprequest.js” and initiate it by entering a command like as shown following in node.js command prompt.

 

Initiate Http Module Query String Example in Node.js Command Prompt

 

Now your computer will work as server so if you tries to access http://localhost:4200/tutlane URL, then in return you will get the response like as shown below.

 

Node.js Http Module Query String Example Result

 

In case, if you change the url like http://localhost:4200/nodejs and click enter you will get the response like as shown below.

 

Node.js Http Module Query String Example Result

 

Like this, we can get and perform multiple operations on HTTP server request. We will learn more about HTTP server request in further chapters.

Node.js Handle Errors in HTTP Server

Generally, while working with HTTP server there might be a chance that we will get an exception so in node.js, we can handle those exceptions like as shown below.

 

var http = require('http');

const server = http.createServer(function (req, res) {

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

res.write('Hello World!');

res.end();

});

// It will handle the errors in server

server.on('error', (err) => {

    throw err;

});

server.listen(4200, () => {

    console.log('Server listening on port : 4000');

});

This is how we can use HTTP module in node.js to perform multiple operations like creating a HTTP server that listens on particular port to handle request and response based on our requirements. 

 

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