What is HTTP ?

HTTP (Hypertext Transfer Protocol) is a fundamental protocol of the Internet, enabling the transfer of data between a client and a server. It is the foundation of data communication for the World Wide Web.

HTTP provides a standard between a web browser and a web server to establish communication. It is a set of rules for transferring data from one computer to another. Data such as text, images, and other multimedia files are shared on the World Wide Web. Whenever a web user opens their web browser, the user indirectly uses HTTP. It is an application protocol that is used for distributed, collaborative, hypermedia information systems.

History of HTTP

• Tim Berners-Lee and his team at CERN are indeed credited with inventing the original HTTP protocol.
• HTTP version 0.9 was the initial version introduced in 1991.
• HTTP version 1.0 followed in 1996 with the introduction of RFC 1945.
• HTTP version 1.1 was introduced in January 1997 with RFC 2068, later refined in RFC 2616 in June 1999.
• HTTP version 2.0 was specified in RFC 7540 and published on May 14, 2015.
• HTTP version 3.0, also known as HTTP/3, is based on the QUIC protocol and is designed to improve web performance. It was renamed as Hyper-Text Transfer Protocol QUIC (HTTP/3) and developed by Google.

Methods of HTTP

• GET: Used to retrieve data from a specified resource. It should have no side effects and is commonly used for fetching web pages, images, etc.
• POST: Used to submit data to be processed by a specified resource. It is suitable for form submissions, file uploads, and creating new resources.
• PUT: Used to update or create a resource on the server. It replaces the entire resource with the data provided in the request body.
• PATCH: Similar to PUT but used for partial modifications to a resource. It updates specific fields of a resource rather than replacing the entire resource.
• DELETE: Used to remove a specified resource from the server.
• HEAD: Similar to GET but retrieves only the response headers, useful for checking resource properties without transferring the full content.
• OPTIONS: Used to retrieve the communication options available for a resource, including supported methods and headers.
• TRACE: Used for debugging purposes to echo the received request back to the client, though it’s rarely used due to security concerns.
• CONNECT: Used to establish a tunnel to the server through an HTTP proxy, commonly used for SSL/TLS connections.

HTTP Request/Response:

HTTP is a request-response protocol, which means that for every request sent by a client (typically a web browser), the server responds with a corresponding response. The basic flow of an HTTP request-response cycle is as follows:

• Client sends an HTTP request: The client (usually a web browser) initiates the process by sending an HTTP request to the server. This request includes a request method (GET, POST, PUT, DELETE, etc.), the target URI (Uniform Resource Identifier, e.g., a URL), headers, and an optional request body.
• Server processes the request: The server receives the request and processes it based on the requested method and resource. This may involve retrieving data from a database, executing server-side scripts, or performing other operations.
• Server sends an HTTP response: After processing the request, the server sends an HTTP response back to the client. The response includes a status code (e.g., 200 OK, 404 Not Found), response headers, and an optional response body containing the requested data or content.
• Client processes the response: The client receives the server’s response and processes it accordingly. For example, if the response contains an HTML page, the browser will render and display it. If it’s an image or other media file, the browser will display or handle it appropriately.

HTTP Request Circle

Requested Resource	Resource Type	Server Response
HTML Page	HTML	Server sends HTML file
Style Sheet (CSS)	CSS	Server sends CSS file
Image (JPG)	Image (JPG)	Server sends JPG image
JavaScript Code	JavaScript (JS)	Server sends JS file
Data (XML or JSON)	Data	Server sends XML/JSON data

Overview of HTTP Request and Response Components

Concept	Description
HTTP Request Headers	Text information in key-value pairs sent with every HTTP request, conveying details such as client’s browser, requested data, and more.
HTTP Request Body	Contains data being submitted to the web server, such as form inputs, authentication details, or other payload data.
HTTP Response	Sent by the server in answer to an HTTP request, consisting of an HTTP status code, response headers, and optional response body.
HTTP Status Codes	3-digit codes indicating the outcome of an HTTP request, categorized into 1xx (Informational), 2xx (Success), 3xx (Redirection), 4xx (Client Error), and 5xx (Server Error) blocks.
HTTP Response Headers	Provide important information like data format, language, and content type in the response, helping clients interpret the data correctly.
HTTP Response Body	Contains the requested information sent by the server, such as HTML content for webpages, JSON data, or other data based on the client’s request.

Features

• Stateless: Each request is independent, and the server doesn’t retain previous interactions’ information.
• Text-Based: Messages are in plain text, making them readable and debuggable.
• Client-Server Model: Follows a client-server architecture for requesting and serving resources.
• Request-Response: Operates on a request-response cycle between clients and servers.
• Request Methods: Supports various methods like GET, POST, PUT, DELETE for different actions on resources.

Advantages

• Platform independence: Works on any operating system
• Compatibility: Compatible with various protocols and technologies
• Efficiency: Optimized for performance
• Security: Supports encryption for secure data transfer

Disadvantages

• Lack of security: Vulnerable to attacks like man in the middle
• Performance issues: Can be slow for large data transfers
• Statelessness: Requires additional mechanisms for maintaining state