事件：'close'

【Event: 'close'】

'close' 事件在使用 close() 关闭套接字后触发。一旦触发，该套接字将不再发出新的 'message' 事件。

【The 'close' event is emitted after a socket is closed with close(). Once triggered, no new 'message' events will be emitted on this socket.】