Re: Winsock select timeout

"Scott McPhillips [MVP]" <org-dot-mvps-at-scottmcp>
Wed, 17 Oct 2007 11:57:19 -0400
<> wrote in message


1) Since i'm communicating with a serial hub (each serial hub is
capable of communicating with 16 RS232 devices). The UDP messages
coming from the serial will be parallel. So i definitely need to read
parallely.i.e. from multiple threads..

Is there only one network card? If there is only one network card then the
UDP messages cannot arrive in parallel.

2) when i'm reading for response messages on the UDP socket, i want to
make sure the entire message reading loop timesout in <=150 millisec.
Since i'm doing network serial programming, the serial data will be
coming in multiple UDP messages..I want to do multiple reads i.e.
thru' select but timeout exactly/approx at 150 msec. how do i make
sure this can happen. The current code that i'm using is using the
GetTickcount() & this seem to be incorrect..if the thread switching
latency is so can i specify a relative timeout here

dw = GetTickCount()

while ((dw - Gettickcount()) <=150)

nRetValue = select(timeout 100);
if(nRetValue >0)
 recvfrom(); //non-blocking read..

In the above code, how do i ensure this thread really waits for
150msec..excluding the thread switching latency..
Appreciate your help

If you are asking how to prevent the thread switching, you can't. I think
you would do better to make the design event-driven, processing all received
messages when they are received.

Scott McPhillips [VC++ MVP]

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