非阻塞connect

1. int flags = fcntl(sock_fd, F_GETFL, 0);
2.  
   fcntl(sock_fd, F_SETFL, flags|O_NONBLOCK);
3.  
   #else
4.  
   int imode = 1;
5.  
   ioctl(sock_fd, FIONBIO, &imode);