socket.pending
如果套接字尚未连接，则为 true，要么是因为 .connect() 尚未被调用，要么是因为它仍在连接过程中（参见 socket.connecting）。
This is true if the socket is not connected yet, either because .connect()
has not yet been called or because it is still in the process of connecting
(see socket.connecting).