HyperText Transfer Protocol (HTTP)

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HyperText Transfer Protocol (HTTP) enables clients (e.g., web browsers) to request resources from an HTTP server.

• is the foundation of web technology
• process:
  • a client connects to the HTTP server using a TCP port
    • TCP/80 by default
  • client submits a request for a resource (GET)
    • using a uniform resource locator (URL)
  • server acknowledges the request and either responds with the data or with an error message

HTTP Headers and Payload

• response and request formats are defined in the HTTP header
• HTTP payload is usually used to server HyperText Markup Language (HTML) webpages
  • plain text files with coded tags describing how the page should be formatted
  • a web browser can interpret the tags and display the text and other resources associated with the page
    • e.g., binary picture or sound files linked to the page
• HTTP features a forms mechanism (POST)
  • enables a user to submit data from the client to the server
• HTTP is a stateless protocol
  • means that the server is not required to preserve information about the client during a session
  • however, the basic functionality of HTTP servers is often extended by support for scripting and programmable features (web applications)
  • servers can also set text file cookies to preserve session information
• these coding features and integration with databases increase flexibility and interactivity
  • but also increases the attack surface and expose more vulnerabilities

Info

• many argue that HTTP is a stateful protocol
• version 2 of HTTP adds more state-preserving features