udp, select a timeout and receive data recvfrom reasons

wirshark packet capture and found that data. But select timeout, direct recvfrom failed again.

The code needs to be improved: after select a timeout, the handle will be removed when the fd_set collection of Super League, so every time you want to re-FD_SET, and then to select.

Finally: turn off the firewall, to solve this problem.

Reproduced in: https: //www.cnblogs.com/bigfi/p/11020958.html