Http1.1最初定义在Hypertext Transfer Protocol -- HTTP/1.1中，后面被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：

RFC7230:Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing
RFC7231:Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content
RFC7232:Hypertext Transfer Protocol (HTTP/1.1): Conditional Requests
RFC7233:Hypertext Transfer Protocol (HTTP/1.1): Range Requests
RFC7234:Hypertext Transfer Protocol (HTTP/1.1): Caching
RFC7235:Hypertext Transfer Protocol (HTTP/1.1): Authentication

概要

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

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.

HTTP消息格式

HTTP-message   = start-line
                 *( header-field CRLF )
                 CRLF
                 [ message-body ]

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     = request-line / status-line
request-line   = method SP request-target SP HTTP-version CRLF

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)