What is an http upgrade?

最新推荐文章于 2025-02-13 14:50:52 发布

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最新推荐文章于 2025-02-13 14:50:52 发布

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原文链接：http://www.cnblogs.com/huenchao/p/6233669.html

本文介绍了HTTP升级机制，包括其用途和实现方式。该机制允许客户端指定希望使用的其他通信协议，并在可能的情况下请求服务器进行切换。文章还解释了如何通过Upgrade头字段来通知协议变更。

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HTTP Upgrade is used to indicate a preference or requirement to switch to a different version of HTTP or to another protocol, if possible:

The Upgrade general-header allows the client to specify what additional communication protocols it supports and would like to use if the server finds it appropriate to switch protocols.

The server MUST use the Upgrade header field within a 101 (Switching Protocols) response to indicate which protocol(s) are being switched.

   Upgrade        = "Upgrade" ":" 1#product

For example,

   Upgrade: HTTP/2.0, SHTTP/1.3, IRC/6.9, RTA/x11

The Upgrade header field is intended to provide a simple mechanism for transition from HTTP/1.1 to some other, incompatible protocol.

According to the IANA register, there are only 3 registered mentions of it (including one in the HTTP specification itself).

The other two are for:

Upgrading to TLS Within HTTP/1.1 (almost never used, not to be confused with HTTP over TLS, which defines HTTPS as widely used). This upgrade allows for a similar mechanism to STARTTLS in other protocols (e.g. LDAP, SMTP, ...) so as to be able to switch to TLS on the same port as the plain connection, after exchanging some of the application protocol messages, as opposed to having the entire HTTP exchange on top of SSL/TLS without it needing to know it's on top of TLS (the way HTTPS works).
Upgrading to WebSockets (still a draft).

转载于:https://www.cnblogs.com/huenchao/p/6233669.html