In ICA (Citrix Receiver) sessions, when using a USB reader device (such as bar code scanner or credit card reader) in keyboard emulation mode, the output might intermittently be incomplete or corrupted.

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Implement the KeyboardTimer ICA setting on the client system. The KeyboardTimer setting forces the USB and Keyboard inputs to always be processed in the same order, resolving the issue.

Modify or create the KeyboardTimer string in the registry on the client Windows Operating System as shown below.
Note: Restart the Citrix Receiver for the setting to be effective.

For 32-bit systems under Local Machine:
HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\ICA Client\Engine\Lockdown Profiles\All Regions\Lockdown\Virtual Channels\Keyboard
REG_SZ: KeyboardTimer (modify if existent or create if inexistent)
Value: 10
 
For 64-bit systems under Local Machine:
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Citrix\ICA Client\Engine\Lockdown Profiles\All Regions\Lockdown\Virtual Channels\Keyboard
REG_SZ: KeyboardTimer (modify if existent or create if inexistent)
Value: 10
 
For 32/64-bit systems under Current User:
HKEY_CURRENT_USER\Software\Citrix\ICA Client\Engine\Lockdown Profiles\All Regions\Lockdown\Virtual Channels\Keyboard
REG_SZ: KeyboardTimer (modify if existent or create if inexistent)
Value: 10
 
To implement KeyboardTimer in the “default.ica” file on StoreFront:

1. Open C:\inetpub\wwwroot\Citrix\StoreName\App_Data\default.ica file in Notepad.
2. Under the [WFClient] section of the file, add the following line: KeyboardTimer=10
3. Save the default.ica file.
4. Open the command prompt (cmd) and run iisreset.

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Problem Cause

With Receiver 3.x and later, the USB and Keyboard inputs is being processed asynchronously. This change was done with performance improvements in mind. The speed at which a keyboard-emulation device transmits the emulated keystrokes to the OS if beyond speeds of human typing can sometimes cause the missing/corrupted data.

Missing or Corrupted Output Data with USB Devices in Keyboard Emulation Mode

Citrix Documentation - ICA Settings Reference - KeyboardTimer