[Rxtx] Questions about the Rewrite2010

[Kustaa Nyholm]

Adrian,

had a look at your code/rewrite and it looks rather clean/nice.

I was looking at the code to gain insight (not related to the
rewrite) into what is involved in serial port programming
in Windows. Or rather, to refresh my memory and see how others have
done, because I've been there done that.

So my questions are just to satisfy my curiosity, not to criticize
or suggest improvements.

1) It looks like a new thread (EventMonitor) is created for
each Serial port, is that correct?

Many people seem to try to avoid using many threads in this sort
of situation, and like to use something like unix select().
I personally find using threads more natural and better impedance
match to the problem being solved here. I guess 'many people' above

refers to those implementing thousands of connections and
who cannot live with the overhead and limited number of threads
available.

2) The EventMonitor basically polls for events at 50 msec interval?

3) There is a comment in the source code near the sleep(50) :

// Sufficient up to 19200 baud


I'm sure you thought about this carefully, so again not
criticizing, but seeking to understand how or why, because
at 50 msec would seem to limit through in some cases. Like
if you send one byte and need to wait for one to return,
then this limits speed to 200 chars/sec?

4) I've done something similar to a few years back from
Java using JNI to access Win32 API serial port, and
I seem to recall that I had threading issues ie when
I submitted a read (ReadFile) and there was no data coming
in, the thread would not only block but also consume a
lot of CPU cycles ie it was not sleeping properly inside
the ReadFile call when the serial port blocked.

Im a bit fuzzy about the details after five years, so my question is
have you checked if  there an issue here?


5) AFAIK the select() on Windows does not work serial ports
but there is some other mechanism (events?) to implement the
same functionality, did you consider that? Probably, so you
decided against it, why?


br Kusti