HTTP: The Definitive Guide

Name

Connection

Synopsis

The Connection header is a somewhat overloaded header that can lead to a bit of confusion. This header was used in HTTP/1.0 clients that were extended with keep-alive connections for control information.^[4] In HTTP/1.1, the older semantics are mostly recognized, but the header has taken on a new function.

In HTTP/1.1, the Connection header’s value is a list of tokens that correspond to header names. Applications receiving an HTTP/1.1 message with a Connection header are supposed to parse the list and remove any of the headers in the message that are in the Connection header list. This is mainly for proxies, allowing a server or other proxy to specify hop-by-hop headers that should not be passed along.

One special token value is “close”. This token means that the connection is going to be closed after the response is completed. HTTP/1.1 applications that do not support persistent connections need to insert the Connection header with the “close” token in all requests and responses.

Type

General header

Notes

While RFC 2616 does not specifically mention keep-alive as a connection token, some browsers (including those sending HTTP/1.1 as their versions) use it in making requests.

Basic Syntax

Connection: 1# (connection-token)

Examples

Connection: close

^[4] See Chapter 4 for more on keep-alive and persistent connections.