验证码：够了吗？(Captcha: is it enough?)

 在服务器端，侦听套接字仅与本地IP和端口关联，并处于LISTEN状态。 
 
 相反，服务器上接受的套接字（以及客户端上连接的套接字）由本地IP和端口以及远程IP和端口标识，并处于ESTABLISHED状态。 
 
 在客户端，服务器使用与连接的套接字分开的侦听套接字并不重要。 当客户端从connect返回时，服务器已经从accept并且从每个返回的套接字描述符可以相互通信。 

On the server side, the listening socket is associated with only a local IP and port and is in the LISTEN state.
 
In contrast, accepted sockets on the server (as well as connected sockets on the client) are identified by a local IP and port as well as a remote IP and port and is in the ESTABLISHED state.
 
On the client side, it doesn't matter that the server uses a listening socket separate from the connected socket. By the time the client returns from connect, the server has returned from accept and the socket descriptors returned from each can communicate with each other.