Alternative to blocking socket we can have non-blocking socket. Any call on these socket will return without blocking.
Following code illustrates how to create a non-blocking socket.
SOCKET s;
unsigned long ulMode = 1;
int nRet;
s = socket(AF_INET, SOCK_STREAM, 0);
nRet = ioctlsocket(s, FIOBIO, (unsigned long *) &ulMode);
if (nRet == SOCKET_ERROR)
{
//Failed to put the socket into nonblocking mode
}
Here ulMode value 1 enables socket non-blocking mode.
changing this value to 0 disables non-blocking mode.
The WSAAsyncSelect and WSAEventSelect functions automatically set a socket to nonblocking mode. If WSAAsyncSelect or WSAEventSelect has been issued on a socket, then any attempt to use ioctlsocket to set the socket back to blocking mode will fail with WSAEINVAL.
To set the socket back to blocking mode, an application must first disable WSAAsyncSelect by calling WSAAsyncSelect with the lEvent parameter equal to zero, or disable WSAEventSelect by calling WSAEventSelect with the lNetworkEvents parameter equal to zero.
