【HTTP Persistent Connection】
1、HTTP1.0 Persistent Connection实现：
2、HTTP1.0 Persistent Connection图解：
3、HTTP1.0 Persistent Connection参数：
4、HTTP1.1 Persistent Connection
A significant difference between HTTP/1.1 and earlier versions of HTTP is that persistent connections are the default behavior of any HTTP connection. That is, unless otherwise indicated, the client SHOULD assume that the server will maintain a persistent connection, even after error responses from the server.
