COM Port Redirection: How to map a client COM port to a server COM port

LPT and COM port settings are configurable via Studio in XenApp / XenDesktop 7.9 or newer. In versions 7.0 through 7.8, these settings were only configurable using the registry. For more information, see Port redirection policies in Citrix Documentation.

Client COM port mapping allows devices attached to the COM ports on the user’s endpoint to be used during virtual sessions. These mappings can be used like any other network mappings.

For each COM port, a driver in the OS assigns a symbolic link name such as COM1, COM2, etc, which is then utilized by the applications to access the port.

While most PCs no longer have built-in serial (COM) ports, the ports are easy to add via USB converters.

Beware that even if a device can attach to the endpoint via USB directly does not mean it can be redirected via Generic USB Redirection. Some USB devices function as virtual COM ports, which applications can access in the same way as physical serial port. The OS can abstract COM ports and treat them like fileshares. Two common protocols for virtual COM are CDC ACM or MCT.

(When connected through RS-485 port Applications might not work at all. Get a RS-485-to-RS232 converter to use it as a COM port)

Applications suited for serial ports often involve sensors, controllers, old check readers, pads, etc.

Some USB virtual COM-port devices use vendor-specific drivers in place of the Windows-provided drivers (usbser.sys).

These drivers allow you to force the virtual COM port of the USB device so that it does not change even if connected to different USB sockets. This might be done from Device Manager / Ports (COM & LPT) / Properties, or from the Application itself, that controls the Device.

User-added image

Warning: Some applications will only recognize the Device (e.g. signature pad) consistently if it is connected to COM1 or COM2 on the client workstation.


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