HTTP protocol
The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypermedia information systems. 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 provides the capability not only for your web browser to request pages and files from the webserver, but also HTTP provides the ability for your browser to send information back to the server. Usually this information is in the form of text box information, check boxes, and radio buttons you click on or fill out when you register on a particular website, respond to a poll, or submit any form.
HTTP characteristics
- Stateless - Each transaction between the client and server is independent and no state is set based on a previous transaction or condition.
- Uses requests from the client to the server and responses from the server to the client for sending and receiving data.
The HTTP protocol is a request/response protocol. A client sends a request to the server in the form of a request method, URI, and protocol version, followed by a MIME-like message containing request modifiers, client information, and possible body content over a connection with a server. The server responds with a status line, including the message's protocol version and a success or error code, followed by a MIME-like message containing server information, entity metainformation, and possible entity-body content.
Most HTTP communication is initiated by a user agent and consists of a request to be applied to a resource on some origin server. In the simplest case, this may be accomplished via a single connection between the user agent and the origin server.
A more complicated situation occurs when one or more intermediaries are present in the request/response chain. There are three common forms of intermediary: proxy, gateway, and tunnel.
A proxy is a forwarding agent, receiving requests for a URI in its absolute form, rewriting all or part of the message, and forwarding the reformatted request toward the server identified by the URI.
A gateway is a receiving agent, acting as a layer above some other server(s) and, if necessary, translating the requests to the underlying server's protocol.
A tunnel acts as a relay point between two connections without changing the messages; tunnels are used when the communication needs to pass through an intermediary (such as a firewall) even when the intermediary cannot understand the contents of the messages.
In HTTP/1.0, most implementations used a new connection for each request/response exchange. In HTTP/1.1, a connection may be used for one or more request/response exchanges, although connections may be closed for a variety of reasons.
HTTP Methods
The HTML specifications technically define the difference between GET and POST:
GET means that form data is to be encoded (by a browser) into a URL, it creates a query string of the name-and-value pairs and then appends the query string to the URL of the script on the server that handles the request.
While the POST means that the form data is to appear within a message body, it passes the name-and-value pairs in the body of the HTTP request message
Secure HTTP (HTTPS)
HTTP is insecure and is subject to man-in-the-middle and eavesdropping attacks which can let attackers gain access to website accounts and sensitive information. HTTPS is designed to withstand such attacks and is secure.
HTTPS can create a secure channel over an insecure network.
