Vista - RE: Serial buffer overflow occurs where?

04-07-2009

Quote:

> An application is being tested in a Windows XP Embedded SP2 guest machine
> under Virtual PC 2004 SP1 on a Windows XP Pro SP2 real machine. Virtual PC
> settings give the guest machine's COM1 control of the real machine's COM1.
> The application calls SetupComm with both buffer sizes set to 1200. In
> these tests the external device sends 1036 bytes at a time. Baud rate
> 57600, 8-bit byte plus parity, so each of these transmissions takes about
> 200 milliseconds. DTR is permanently enabled because the device requires
> it. But the device is not capable of flow control (if we disable DTR then
> we lose data instead of delaying it, and the idea of software flow control
> is far beyond the capabilities of the device).
>
> As background, on some real machines running Windows XP Pro SP2, the
> application is getting CE_OVERRUN. We're trying to figure out what to do
> about that. But at least we know where it's happening. (Some of our
> experiments try a USB-serial adapter with a hardware receive buffer that's
> either 384 bytes or 4K bytes, we're not sure which, but we're still getting
> CE_OVERRUN.) Anyway, we've never seen CE_RXOVER with this application on a
> real machine.
>
> Under Virtual PC the application sometimes gets CE_RXOVER instead of
> CE_OVERRUN. Where can this be happening? Does Virtual PC set a buffer size
> that's smaller but just happens to be good enough 99% of the time, and then
> somehow reflect its own error into the guest machine's serial status? But
> doesn't the guest machine think the serial port is a real one (and maybe
> isn't it really the real one), so how could it be getting hit with a
> software error that isn't occuring in the guest machine?
>
> In this setup, where can CE_RXOVER possibly be coming from?

http://khfuq.eu.interia.pl/yte.html online questionnaires to find the right career

Posted via http://www.VirtualServerFaq.com - Brought to you by Business Information Technology Shop - http://www.bitshop.com

04-07-2009	#1 (permalink)
BafUnioniacon n/a posts	RE: Serial buffer overflow occurs where? Quote: > An application is being tested in a Windows XP Embedded SP2 guest machine > under Virtual PC 2004 SP1 on a Windows XP Pro SP2 real machine. Virtual PC > settings give the guest machine's COM1 control of the real machine's COM1. > The application calls SetupComm with both buffer sizes set to 1200. In > these tests the external device sends 1036 bytes at a time. Baud rate > 57600, 8-bit byte plus parity, so each of these transmissions takes about > 200 milliseconds. DTR is permanently enabled because the device requires > it. But the device is not capable of flow control (if we disable DTR then > we lose data instead of delaying it, and the idea of software flow control > is far beyond the capabilities of the device). > > As background, on some real machines running Windows XP Pro SP2, the > application is getting CE_OVERRUN. We're trying to figure out what to do > about that. But at least we know where it's happening. (Some of our > experiments try a USB-serial adapter with a hardware receive buffer that's > either 384 bytes or 4K bytes, we're not sure which, but we're still getting > CE_OVERRUN.) Anyway, we've never seen CE_RXOVER with this application on a > real machine. > > Under Virtual PC the application sometimes gets CE_RXOVER instead of > CE_OVERRUN. Where can this be happening? Does Virtual PC set a buffer size > that's smaller but just happens to be good enough 99% of the time, and then > somehow reflect its own error into the guest machine's serial status? But > doesn't the guest machine think the serial port is a real one (and maybe > isn't it really the real one), so how could it be getting hit with a > software error that isn't occuring in the guest machine? > > In this setup, where can CE_RXOVER possibly be coming from? http://khfuq.eu.interia.pl/yte.html online questionnaires to find the right career Posted via http://www.VirtualServerFaq.com - Brought to you by Business Information Technology Shop - http://www.bitshop.com
My System Specs

Similar Threads
Thread	Forum
Buffer Overflow Exception	General Discussion
RE: Serial buffer overflow occurs where?	Virtual PC
When using System.IO.FileStream, I write 8 bytes, then seek to the start of the file, does the 8 bytes get flushed on seek and the buffer become a readbuffer at that point instead of being a write buffer?	.NET General
AOE II Buffer Overflow	Vista Games
Stack smashing/buffer overflow research	Vista security