Getting started with HTTP

HTTP/2

HTTP requests and responses

HTTP clients and servers send HTTP requests and responses, respectively

HTTP describes how an HTTP client, such as a web browser, sends an HTTP request via a network to an HTTP server, which then sends an HTTP response back to the client.

The HTTP request is typically either a request for an online resource, such as a web page or image, but may also include additional information, such as data entered on a form. The HTTP response is typically a representation of an online resource, such as a web page or image.

HTTP/1.0

HTTP/1.1

HTTP/0.9

The first version of HTTP that came into existence is 0.9, often referred to as “HTTP As Implemented.” A common description of 0.9 is “a subsect of the full HTTP [i.e. 1.0] protocol.” However, this greatly fails to illustrate the disparity in capabilities between 0.9 and 1.0.

Neither requests nor responses in 0.9 feature headers. Requests consist of a single CRLF-terminated line of GET, followed by a space, followed by the requested resource URL. Responses are expected to be a single HTML document. The end of said document is marked by dropping the connection server-side. There are no facilities to indicate success or failure of an operation. The only interactive property is the search string which is closely tied to the <isindex> HTML tag.

Usage of HTTP/0.9 is nowadays exceptionally rare. It is occasionally seen on embedded systems as an alternative to tftp.