WEB SERVER with Node.js

WEB SERVER

The term web server can refer to both side the hardware and the software , or both of them working together.

1. The hardware side = A web server is a computer that stores web software or website component files. A web server connects to the internet and support physical data interchange with other devices connected to the web.

2. The Software side = A web server includes several parts that control how web users access hosted files. At minimum this is an HTTP server. An HTTP server is a software that understands the URLs and HTTP.

   An overview of HTTP

   HTTP is a protocol for fetching resources such as HTML Documents. It is the foundation of any data exchange on the Web and it is a client-server protocol, which means requests are initiated by the recipient, usually the Web browser.

   Clients and servers communicate by exchanging individual messages (as opposed to a stream of data). The messages sent by the client, usually a Web browser, are called requests and the messages sent by the server as an answer are called responses.

   HTTP request methods

   HTTP defines a set of request methods to indicate the desired action to be performed for a given resource. Although they can also be nouns, these request methods are sometimes referred to as HTTP verbs.

   [GET](<https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods/GET>)

   The GET method requests a representation of the specified resource. Requests using GET should only retrieve data.

   [HEAD](<https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods/HEAD>)

   The HEAD method asks for a response identical to a GET request, but without the response body.

   [POST](<https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods/POST>)

   The POST method submits an entity to the specified resource, often causing a change in state or side effects on the server.

   [PUT](<https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods/PUT>)

   The PUT method replaces all current representations of the target resource with the request payload.

   [DELETE](<https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods/DELETE>)

   The DELETE method deletes the specified resource.

   HTTP response status codes

   HTTP response status codes indicate whether a specific HTTP request has been successfully completed. Responses are grouped in five classes:

   1. Informational responses (100 – 199)

   2. Successful responses (200 – 299)

   3. Redirection messages (300 – 399)

   4. Client error responses (400 – 499)

   5. Server error responses (500 – 599)

Origin => Two URLs have the same origin if the protocol, port and host are same for both.

Same origin Policy => It is a critical security mechanism that restricts how a document or script loaded by one origin can interact with a resource from another origin.

COR => Cross origin request = In browser terminology, the current browser URL is called the current origin and the third-party URL is cross-origin.

When you make a cross-origin request, this is the request-response process:

1. The browser adds an origin header to the request with information about the current origin's protocol, host, and port.

CORS = Cross Origin Resource Sharing = CORS (Cross-Origin Resource Sharing) is a system, consisting of transmitting HTTP headers, that determines whether browsers block frontend JavaScript code from accessing responses for cross-origin requests.