Is there any way to monitor the modem signals on a Linux comm port? Maybe using an IOCTL call?
I need to monitor DSR, CTS, etc. from an application program.
How about on a Windows XP platform?
I assume you mean monitor it without actually being the application to open the port? If so, here is source-code and a sample tool that monitors COM and LPT ports on Windows (including XP).
There’s a linux program called statserial and another one called modemstat which both will monitor the lines you are interested in. The source code for those should give you exactly what you want.
Yes, this looks like what I need right here. Thanks.
Any ideas for Widows XP systems out there?
Doesn’t my link cover XP?
I can’t seem to find the source. It does look like what I need, but I need to “program” this capability into my program.
http://www.commstudio.com/commstudio/ActiveX.aspx
Maybe try this. I used to use PDQComm when I needed to do modem stuff from VB, this looks like the current version of the package.
I think I need something that will work from a C/C++ interface. I tried rifling through all the low-level I/O control calls but I was unable to find exactly what I need. Perhaps something in this area will do? I need to take a closer look. Thanks for all your responses. ACK 
Sorry about that; you’re right. They used to publish the source-code for almost all of the tools. The point of the site was to both provide cool tools and teach how they worked. Now I only see source for a few tools.
If you are still looking, you might drop the authors an email requesting source.