/* Set the I/O mode of the socket */
if (blocking_option) {
lret = 1L; /* 非阻塞模式 */
ioctlsocket(sd, FIONBIO, (u_long FAR *) &lret);
}
else {
lret = 0L; /* 阻塞模式 */
ioctlsocket(sd, FIONBIO, (u_long FAR *) &lret);
}