How Can I Reliably Close a Virtual Serial Port After Unplugging a USB Barcode Scanner?

Unplugging a Virtual Serial Port

You're facing an issue with an unplugged USB barcode scanner that keeps your software's virtual port open indefinitely when accessed through the "SerialPort" class. To address this, the following considerations are vital:

USB serial ports emulate the classic serial ports, which lack native Plug and Play support. Despite this, most USB drivers opt to close virtual ports upon device removal, ensuring that your code can respond accordingly. However, some drivers may fail to do so, leaving the port open indefinitely.

Diagnosing and resolving this issue is challenging due to the limited diagnostic capabilities of the SerialPort class. To mitigate the problem, consider the following strategies:

• Use the latest .NET version: Microsoft has implemented patches in newer .NET releases to minimize issues with unreliable drivers.
• Contact the vendor: Request an updated driver to improve driver functionality.
• Close the port gracefully: Make closing the port easy and accessible within your user interface to handle device removal manually.

While relying on Plug and Play support in USB driver design would ideally resolve the issue, most drivers lack this feature. As a result, you may encounter unpredictability with different driver implementations when attempting to close a port with an unplugged device.

To prevent this problem, best practices include:

• Always use the "Remove Hardware Safely" option in Windows.
• Contact vendors to report unreliable drivers.
• Glue the USB connector in place to prevent accidental disconnections.

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