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1. Introduction

1.2 Overall Operation

The HTTP protocol is based on a request/response paradigm. A requesting program (termed a client) establishes a connection with a receiving program (termed a server) and 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. The server responds with a status line (including its protocol version and a success or error code), followed by a MIME-like message containing server information, entity metainformation, and possible body content. It should be noted that a given program may be capable of being both a client and a server; our use of those terms refers only to the role being performed by the program during a particular connection, rather than to the program's purpose in general.

On the Internet, the communication generally takes place over a TCP/IP connection. The default port is TCP 80 [17], but other ports can be used. This does not preclude the HTTP/1.0 protocol from being implemented on top of any other protocol on the Internet, or on other networks. The mapping of the HTTP/1.0 request and response structures onto the transport data units of the protocol in question is outside the scope of this specification.

For most implementations, the connection is established by the client prior to each request and closed by the server after sending the response. However, this is not a feature of the protocol and is not required by this specification. Both clients and servers must be capable of handling cases where either party closes the connection prematurely, due to user action, automated time-out, or program failure. In any case, the closing of the connection by either or both parties always terminates the current request, regardless of its status.

T. Berners-Lee, R. T. Fielding, H. Frystyk Nielsen - 12 MAR 95

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