Re: Immediate IO in ReadFile / WriteFile

[Mike McCormack]

Hey Martin,

As Lawson said, some programs use WaitForComm event to wait for data,
then GetCommError to check how many bytes arrived, then ReadFile to
read it. They then expect ReadFile to return TRUE.

One such program is VBTerm, the visual basic terminal program, or at
least the VBX in it.

Testing applications that use serial ports is difficult, and debugging
often must be done remotely. (eg. send me a trace like this, apply
this patch and send me another trace, etc.)

After making a change, i usually get a terminal program (such as
KoalaTerm) and send a couple of "AT" commands to it... :-)

Mike

Original message from: [e-mail]
> On Wed, 9 Jan 2002, Martin Wilck wrote:
> ....
> > How do you check if data is ready in Windows? I didn't find a

select()
> > equivalent, nor is it possible to wait on file handles.
>
> GetCommError and some other functions, I think, returns

lpStat->cbInQue,
> which is in effect the number of characters immediately available to

be
> read.
> > Martin
>
> Lawson

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Immediate IO in ReadFile / WriteFile

[Dan Kegel]

Mike McCormack wrote:
> As Lawson said, some programs use WaitForComm event to wait for data,
> then GetCommError to check how many bytes arrived, then ReadFile to
> read it. They then expect ReadFile to return TRUE.
>
> One such program is VBTerm, the visual basic terminal program, or at
> least the VBX in it.
>
> Testing applications that use serial ports is difficult, and debugging
> often must be done remotely. (eg. send me a trace like this, apply
> this patch and send me another trace, etc.)

For what it's worth, I documented some overlapped serial I/O quirks
some time ago at 
http://www.alumni.caltech.edu/~dank/overlap.htm
I also have a little running sample code there.

- Dan