Win 2000 -- Comm Serial port gets lost


Thread Starter


Wondering if anyone has seen a problem with MSComm that we get at a variety of customer sites. We haven't seen a pattern yet, except that
the problem only happens with Win2000 (Win95/98/ME/NT are fine). e.g. The exact same code works fine in Win98.

PC just loses the COMM port (happens a lot if there is a reboot - but that might be a symptom rather than a cause). This happens on
multiple PC manufacturers and different processors.

Device Manager shows the port OK and there are "no conflicts" on the property page. If we unInstall and then do a PnP search it reInstalls
fine and they are back up and running. Until ....

Spent 3+ hours with MS Support again today. Getting shuttled between various groups - no luck.

We did a small project in VB and we can get an error # 8015 "Incorrect parameters..." once the port is lost -- just by doing the Port Open
command. Since it works 98% of the time we can't seem to make it fail, but once it does it fail, it remains that way until the re-install.

Would appreciate your help if you have seen this action OR resources you might suggest.
I searched for a solution to a similar problem today and even though I did not find what I needed I think I found a fix to your problem. See MS knowledge base Q112841: the COM port settings in the control panel has no effect on COM port settings in a command prompt window.
The fix would be to set your COM port in DOS before you start your application. This needs to be done after each re-boot as it resets to default.

Adrian Jones

I am writing a VB5 application, to run under Windows 2000, reading data from COM1. The data takes the form of 16 text characters sent every 10ms. Most of the time I can read this data without any problem but sometimes the program just stops seeing the data arriving at the port (no on comm events are generated and the input buffer stays empty). I used to run a similar program under Win95 and had no problem. The only way I have found to "restart" the port is to send some output text to the port but this is not ideal.

Any new developments on how to fix this?