What is HTTP?

Hypertext Transfer Protocol. An application layer network protocol for data exchange.

Main features:

• Client-server architecture: The client (e.g., browser) sends a request to the server, which processes it and returns a response.
• Stateless: Each request is processed independently of previous ones. Session state is maintained at higher levels (e.g., using cookies).
• Uses TCP: The default transport protocol is TCP, ensuring reliable data delivery.
• Port 80: The standard port for HTTP.
• HTTP request methods (verbs): Define the type of action to perform on a resource.
  • GET: Request data from a specified resource.
  • POST: Send data for processing or creating a new resource.
  • PUT: Update an existing resource or create a new one at the specified URI.
  • DELETE: Remove the specified resource.
  • PATCH: Partially update a resource.
  • HEAD: Request response headers, similar to GET but without the response body.
  • OPTIONS: Request information about available methods and other communication options for the target resource.
• Response status codes: Three-digit numbers indicating the result of the request.
  • 1xx: Informational
  • 2xx: Success - 200 OK
  • 3xx: Redirection
  • 4xx: Client Error - 404 Not Found
  • 5xx: Server Error - 500 Internal Server Error

HTTP message structure:

Part	Request	Response
Start line	Method URI HTTP Version (e.g., GET / HTTP/1.1)	HTTP Version Status Code Status Phrase (e.g., HTTP/1.1 200 OK)
Headers