If you are either using Windows API functions to communicate through
the serial port or if you are using the MSComm ActiveX control that
comes with Visual Basic 6, then your code should work just fine no
matter what OS version you are using.
What type of error are you seeing? Are you able to open the COM port
but are not able to send or receive data or does your code fail when
you try to open the port?
If the code fails when you try to open the port, then it may be
related to the following problem:
If the device that you have connected to your serial port sends data
continuously and you are running Windows NT/2K/XP, then the problem
may be that Windows thinks that the device is a serial mouse and is
installing the mouse driver for the COM port when you first boot up.
The following URL contains more inforamtion on how to fix this type of
problem.
http://www.taltech.com/support/troublsht/NTDetect.htm
If you are able to open the port and cannot send or receive data then
the problem may be hardware related. Check that the ribbon cable that
goes from the motherboard to the COM port on the back of the PC is
plugged in correctly. You might also try using the Hyperterminal
program that comes with Windows to open the port to see if you can
send and receive data from it. If you can communicate using
Hyperterminal, then the problem is in your code - perhaps you have the
wrong serial communications parameters.
If you cannot send or receive data with Hyperterminal, then you most
likely have some other hardware problem - a bad cable, etc.
