查看“︁HTTP/1.1”︁的源代码

Http1.1最初定义在[https://datatracker.ietf.org/doc/html/rfc2616 Hypertext Transfer Protocol -- HTTP/1.1]中，后面被[https://datatracker.ietf.org/doc/html/rfc7230 Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing]废除，因此当前HTTP1.1协议实际上包括：

* [https://datatracker.ietf.org/doc/html/rfc7230 RFC7230]:Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing
* [https://datatracker.ietf.org/doc/html/rfc7231 RFC7231]:Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content
* [https://datatracker.ietf.org/doc/html/rfc7232 RFC7232]:Hypertext Transfer Protocol (HTTP/1.1): Conditional Requests
* [https://datatracker.ietf.org/doc/html/rfc7233 RFC7233]:Hypertext Transfer Protocol (HTTP/1.1): Range Requests
* [https://datatracker.ietf.org/doc/html/rfc7234 RFC7234]:Hypertext Transfer Protocol (HTTP/1.1): Caching
* [https://datatracker.ietf.org/doc/html/rfc7235 RFC7235]:Hypertext Transfer Protocol (HTTP/1.1): Authentication

= 概要 =
<pre>
GET /hello.txt HTTP/1.1
User-Agent: curl/7.16.3 libcurl/7.16.3 OpenSSL/0.9.7l zlib/1.2.3
Host: www.example.com
Accept-Language: en, mi
</pre>

<pre>
HTTP/1.1 200 OK
Date: Mon, 27 Jul 2009 12:28:53 GMT
Server: Apache
Last-Modified: Wed, 22 Jul 2009 19:15:56 GMT
ETag: "34aa387-d-1568eb00"
Accept-Ranges: bytes
Content-Length: 51
Vary: Accept-Encoding
Content-Type: text/plain

Hello World! My payload includes a trailing CRLF.
</pre>

= HTTP消息格式 =
<syntaxhighlight lang="python">
HTTP-message   = start-line
                 *( header-field CRLF )
                 CRLF
                 [ message-body ]
</syntaxhighlight>

程序首先读取start-line以及header，然后根据header里面的内容决定是否含有body。body则按照长度读取定长字节。

== start-line ==
<syntaxhighlight lang="python">
start-line     = request-line / status-line
request-line   = method SP request-target SP HTTP-version CRLF
status-line    = HTTP-version SP status-code SP reason-phrase CRLF
</syntaxhighlight>

其中：

* HTTP中并未直接定义request-line的长度限制，倘若超过服务端实现所支持的长度，则建议返回501(Not implemented)
* HTTP建议request-line支持至少8000字符长
* 若request-target超过服务器预期则必须返回414 (URI Too Long)

==header-field==
<syntaxhighlight lang="python">
header-field   = field-name ":" OWS field-value OWS

field-name     = token
field-value    = *( field-content / obs-fold )
field-content  = field-vchar [ 1*( SP / HTAB ) field-vchar ]
field-vchar    = VCHAR / obs-text

obs-fold       = CRLF 1*( SP / HTAB )
</syntaxhighlight>

通常header-field是不应该重复，但有一些例外：

* 若该header有多个值，则可以定义为多个<span class="article-label">field-name: field-value</span>或是按照逗号分隔值
* <span class="article-label">Set-Cookie</span>通常会出现多次，但因无法合并到一起，是一个例外

field-value通常只包含US-ASCII 字符集。

对于header的长度HTTP并未直接限制，实际通常根据header的含义在实现上有对应的限制。对于超出预期的请求，规定必须返回4xx错误而不是忽略，以防止 <span class="article-label">HTTP请求夹带技术</span>攻击。

== http body==
因为http的body并不是必须的，具体什么时候有body按照如下的规则：

* 在request中，通过<span class="article-label">Content-Length</span>或者<span class="article-label">Transfer-Encoding</span>定义；
* 在response中，通过请求的method以及响应的状态码确定。HEAD请求不包含body；对于CONNECT请求的2xx响应也没有body；1xx (Informational), 204 (No Content), 以及 304 (Not Modified)也均无body。所有其他response都具有body，即使其长度为0。
===Transfer-Encoding===
Transfer-Encoding用来表明body中的消息是如何编码的，例如
<syntaxhighlight lang="python">
Transfer-Encoding: gzip, chunked
</syntaxhighlight>

表示对body进行了gzip压缩并进行了分组。

<syntaxhighlight lang="java">
transfer-coding    = "chunked" 
                   / "compress"
                   / "deflate"
                   / "gzip"
                   / transfer-extension
     transfer-extension = token *( OWS ";" OWS transfer-parameter )
</syntaxhighlight>

===Content-Length ===
如果不存在<span class="article-label">Transfer-Encoding</span>头，则可通过<span class="article-label">Content-Length</span>表明消息的长度。注意两者不允许同时出现。

<syntaxhighlight lang="python">
Content-Length: 3495
</syntaxhighlight>

==Chunked Transfer Coding==

<syntaxhighlight lang="python">
chunked-body   = *chunk
                 last-chunk
                 trailer-part
                 CRLF
chunk          = chunk-size [ chunk-ext ] CRLF
                 chunk-data CRLF
chunk-size     = 1*HEXDIG
last-chunk     = 1*("0") [ chunk-ext ] CRLF
chunk-data     = 1*OCTET ; a sequence of chunk-size octets
</syntaxhighlight>


[[Category:Network]]