将套接字设置为非阻塞状态

创建一个套接字并将之设置为非阻塞模式：
SOCKET s; 
unsigned long ul = 1; 
int  ret; 
s = socket(AF_INET, SOCK_STREAM, 0); 
ret = ioctlsocket(s, FIONRIO, (unsigned long)&ul); 
if(SOCKET_ERROR==ret) 
{ 
  //未能将套接字设置为非阻塞模式 
}