HTTP Pocket Reference

Name

Connection: options

Synopsis

Specifies options desired for this connection but not for further connections by proxies. For example:

Connection: close

The close option signifies that either the client or server wishes to end the connection (i.e., this is the last transaction). The keep-alive option signifies that the client wishes to keep the connection open. The default behavior of web applications differs between HTTP 1.0 and 1.1.

By default, HTTP 1.1 uses persistent connections, where the connection does not automatically close after a transaction. When an HTTP 1.1 web client no longer has any requests, or the server has reached some preprogrammed limit in spending resources on the client, a Connection: close header indicates that no more transactions will proceed, and the connection closes after the current one. An HTTP 1.1 client or server that doesn’t support persistent connections should always use the Connection: close header.

HTTP 1.0, on the other hand, does not have persistent connections by default. If a 1.0 client wishes to use persistent connections, it uses the keep-alive parameter. A Connection: keep-alive header is issued by both HTTP 1.0 clients and servers for each transaction under persistent connections. The last transaction does not have a Connection: keep-alive header, and behaves like a Connection: close header under HTTP 1.1. HTTP 1.0 servers that do not support persistent connections will not have a Connection: keep-alive header in their response, and the ...