Hypertext Transfer Protocol

Hypertext Transfer Protocol

Developed by	Tim Berners-Lee
Website	{{#statements:P856}}

The Hypertext Transfer Protocol (HTTP) is an application-layer protocol used primarily for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web, where hypertext documents include hyperlinks to other resources that the user can easily access, for example by a mouse click or by tapping the screen in a web browser.

Overview

HTTP was developed by Tim Berners-Lee and his team at CERN starting in 1989. It is a generic, stateless, protocol which can be used for many tasks beyond its use for hypertext, such as name servers and distributed object management systems, through extension of its request methods, error codes, and headers. A feature of HTTP is the typing and negotiation of data representation, allowing systems to be built independently of the data being transferred.

HTTP Session

An HTTP session is a sequence of network request-response transactions. An HTTP client initiates a request by establishing a Transmission Control Protocol (TCP) connection to a particular port on a server (typically port 80, though other ports can be used). An HTTP server listening on that port waits for a client's request message. Upon receiving the request, the server sends back a status line, such as "HTTP/1.1 200 OK", and a message of its own, the body of which may be the requested file, generated content, or an error message. HTTP provides multiple authentication schemes such as basic access authentication and digest access authentication which operate via challenges.

Methods

HTTP defines methods (sometimes referred to as verbs) to indicate the desired action to be performed on the identified resource. These methods include:

• GET - Requests a representation of the specified resource. Requests using GET should only retrieve data.
• HEAD - Asks for a response identical to that of a GET request, but without the response body.
• POST - Submits data to be processed (e.g., from an HTML form) to the identified resource.
• PUT - Uploads a representation of the specified resource.
• DELETE - Deletes the specified resource.
• TRACE - Echoes the received request so that a client can see what (if any) changes or additions have been made by intermediate servers.
• OPTIONS - Returns the HTTP methods that the server supports for the specified URL.
• CONNECT - Converts the request connection to a transparent TCP/IP tunnel.

Status Codes

HTTP status codes are issued by a server in response to a client's request made to the server. They include:

• 1xx (Informational): The request was received, continuing process.
• 2xx (Successful): The request was successfully received, understood, and accepted.
• 3xx (Redirection): Further action needs to be taken in order to complete the request.
• 4xx (Client Error): The request contains bad syntax or cannot be fulfilled.
• 5xx (Server Error): The server failed to fulfill an apparently valid request.

Security

HTTP itself does not provide any encryption, but it can be encapsulated in Transport Layer Security (TLS) to create HTTPS, which is encrypted, thereby providing a secure identification of a network web server. HTTPS is widely used on the Internet for secure communication over a computer network.

Versions

• HTTP/1.0 - The first version of HTTP, which is now obsolete.
• HTTP/1.1 - A revision of the original HTTP that includes persistent connections and more.
• HTTP/2 - The second major version of HTTP, focusing on performance; specifically, end-user perceived latency, network and server resource usage.
• HTTP/3 - The third and upcoming major version of HTTP, which primarily aims to improve security and performance.

See also

• HTTPS
• Internet Protocol Suite
• World Wide Web