'connect' 事件

• request <http.IncomingMessage> HTTP 请求的参数，如它在 'request' 事件中
• socket <stream.Duplex> 服务器和客户端之间的网络套接字
• head <Buffer> 隧道流的第一个数据包（可能为空）

每次客户端请求 HTTP CONNECT 方法时触发。 如果未监听此事件，则请求 CONNECT 方法的客户端将关闭其连接。

除非用户指定 <net.Socket> 以外的套接字类型，否则此事件保证传入 <net.Socket> 类（<stream.Duplex> 的子类）的实例。

触发此事件后，请求的套接字将没有 'data' 事件监听器，这意味着需要绑定它才能处理发送到该套接字上的服务器的数据。

• request <http.IncomingMessage> Arguments for the HTTP request, as it is in the 'request' event
• socket <stream.Duplex> Network socket between the server and client
• head <Buffer> The first packet of the tunneling stream (may be empty)

Emitted each time a client requests an HTTP CONNECT method. If this event is not listened for, then clients requesting a CONNECT method will have their connections closed.

This event is guaranteed to be passed an instance of the <net.Socket> class, a subclass of <stream.Duplex>, unless the user specifies a socket type other than <net.Socket>.

After this event is emitted, the request's socket will not have a 'data' event listener, meaning it will need to be bound in order to handle data sent to the server on that socket.