事件：'close'

¥Event: 'close'

在使用 close() 关闭套接字后会触发 'close' 事件。一旦触发，则此套接字上将不会触发新的 '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.