Re: Serial communication Threading (Thread is blocking)

From:

"Scott McPhillips [MVP]" <org-dot-mvps-at-scottmcp>

Newsgroups:

microsoft.public.vc.mfc

Date:

Fri, 21 Jul 2006 10:31:14 -0400

Message-ID:

<uuqhKJNrGHA.5008@TK2MSFTNGP05.phx.gbl>

harshalshete@gmail.com wrote:

Hi All,

in my application, I am Creating one thread i.e worker thread.

suppose my main thread is A and child thread(worker thread) is B.
i am using this thread for serial communication. this is a blocking
thread.

now in my main application A when i create this thread B i start a
timer.
and i am expecting that in the interval specified in the timer the
operation should
get complete.

otherwise i want to kill the thread B.

but is it possible to kill the serial thread (B) in the context of
thread (A).
means in the timer handler.

and how can we no is there any data is present on the port or not?
we can do this in pipes by calling PeekNamedPipe API

any suggestion will be appriciated.
and one more thing i read in so many articles that calling the
TerminateThread
is the last solution i am not understanding how it will affect the
application.
i think we are just killing a thread. is there something like it's
resources don't get
cleared or something like that.

Thanks and regards
Harshal

You cannot reliably kill thread B from thread A. (And TerminateThread
is not reliable and should never be used.) What you must do is use
overlapped I/O on the port. This will allow you to replace WaitCommEvent
and the blocking ReadFile call with nonblocking calls. Use
WaitForMultipleObjects. WaitForMultipleObjects will let you return when
data is available, and also return when a shutdown event is set by
thread A. In this way thread A can signal to thread B that it should
exit cleanly.

When you use overlapped I/O you do not need to test if data is present
on the port. ReadFile/WaitForMultipleObjects do that for you.

You are trying to reinvent the wheel. You should study the MTTTY sample
code and article in MSDN. They show the best way to handle serial
communications.
<http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnfiles/html/msdn_serial.asp>

--
Scott McPhillips [VC++ MVP]