Recently I ran into some issue related to the UDP sending on Windows. When the application tries to send the packets over UDP in non-blocking mode, often it received socket error 10035 (WSAEWOULDBLOCK) in the send(), so likely that the socket buffer is full. I only seen this issue on Windows 2008 and did not see the same problem on Windows 2003. I was doing some research and found the following article (although it mention TCP) http://support.microsoft.com/kb/823764 At the bottom it mentioned updating of the registry value HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\AFD\Parameters\NonBlockingSendSpecialBuffering to 1 But it didn't include further details Would anyone know what is the effect of setting this registry value and what does it do? I tried to research on the web but unable to find any reference, including the msdn website. Any help would be appreciated.