[Python-Dev] Socket timeout and completion based sockets

Richard Oudkerk shibturn at gmail.com
Mon Nov 26 17:05:04 CET 2012

On 26/11/2012 11:49am, Kristján Valur Jónsson wrote:
> However, other implementations of python sockets, e.g. ones that rely on
> IO completion, may not have the luxury of using select.  For example, on
> Windows, there is no way to abort an IOCP socket call, so a timeout must
> be implemented by aborting the wait.  Dealing with the resulting race
> can be an interesting challenge.

I am not quite sure what you mean by "aborting the wait".  But you can 
abort an overlapped operation using CancelIo()/CancelIoEx().

I have just done some experimenting.

Using CancelIo()/CancelIoEx() to abort an operation started with 
WSARecv() does not seem to cause a problem -- you just call 
GetOverlappedResult() afterwards to check whether the operation 
completed before it could be aborted.

But aborting an operation started with WSASend() sometimes seems to 
"break" the connection: a subsequent WSARecv()/WSASend() will fail with 
WSAECONNABORTED or WSAECONNRESET depending on which end of the 
connection you are on.

So, as you say, if you abort a send then you cannot expect to 
successfully resend the data later.


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