We've run into a similar issue previously but the remedies we took then don't seem to be helping here. Some machines are working fine, others are not.
We are able to open the COM port on all machines in these ways:
- Using the application that originally used the port. It still opens the port and reads from the scanner it's connected to.
- A test application we built that only uses basic IO functions in Microsoft libraries (System.IO.Ports).
Only applications with your component are unable to connect to the port on the unit in question.
As directed before, we tried using the sample application that exports a log file and received these results:
14:24 31.12.2010 - Start: begin COM4
14:24 31.12.2010 - Start: m_bIsOpened is false
14:24 31.12.2010 - Start: open COM4
14:25 31.12.2010 - error: port exist 87
14:25 31.12.2010 - Start: didn't create COM4
14:25 31.12.2010 - Start: end falseCOM4
The OS version on the working machines and the problem machines is Windows XP Pro SP3. We are using the OEM license for Serial Port Sniffer ActiveX Control 4.0. "Virtual Serial Bus Enumerator (Eltima Software)" is present in System Devices and is enabled.
Is there anything else we can try?