Does anyone have any idea what could cause a 10035 error (EWOULDBLOCK) when reading on a blocking socket with a timeout? This is under Windows XP using the .NET framework version 3.5 socket library. I've never managed to get this myself, but one of my colleagues is getting it all the time. He's sending reasonably large amounts of data to a much slower device and then waiting for a response, which often gives a 10035 error. I'm wondering if there could be issues with TCP buffers filling up, but in that case I would expect the read to wait or timeount. The socket is definitely blocking, not non-blocking.