CITRIX – Setup Scanner TWAIN – Policy setup for XEnApp/XenDesktop

This article describes how to set up a scanner to function through an ICA session with XenApp.


Citrix policies must be enabled (depending on the type of scanner)

.Citrix policies must be enabled (depending on the type of scanner)

Other requirements

  • The scanner must be TWAIN compliant
  • The TWAIN drivers must be installed on the local device.  They do not need to be installed on the XenApp server
  • The scanner can be attached locally or can be added using network.
  • Ensure that the scanner is using the local TWAIN driver and not the Windows Image Acquisition service
  • Ensure that there is no policy applied to the user account used for the test that is limiting the bandwidth within the ICA session (client USB redirection bandwidth limit for example)
  • After the Desktop Experience feature is installed, click Close to exit the Add Features Wizard, and then click yes to restart the computer

Remote Desktop Session Host Aware Requirement (Windows 2008 R2)

Some applications are not Remote Desktop Session Host aware. Complete one of the following tasks to allow the application to see the scanner within the RDS session:Copy Twain_32.dll from C:\WINDOWS to the Windows directory of each user within their XenApp profile.

  • C:\Users\UserName\WINDOWS on Windows 2008 R2
  • C:\Documents and Settings\UserName\Windows on Windows 2003

ORCreate a flag within the Terminal Services application compatibility portion of the registry of the XenApp server for that particular application to point the Windows directory of the XenApp server (C:\WINDOWS) instead of the user’s own Windows directory within their XenApp profile.

  1. Navigate to the Application Compatibility Flags portion of the registry:For a 32-bit application:
    HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\Terminal Server\Compatibility\Applications\For an x64-but application:
    KEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Terminal Server\Compatibility\Applications\
  2. Create a Key and name it the same as the name for the application’s executable (that is ADOBE READER)
  3. Create the REG_DWORD value of Flags=0x00000408
    • 0x00000008 = 32 bit application
    • 0x00000400 = refer to system Windows directory
    • that is for an application called Scanner Companion which is 32 bits and on an x64 Windows 2008 R2 XenApp server create the following keyHKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\Terminal Server\Compatibility\Applications\SCANNERCOMPANION\
    • Value

User-added image


To Test scanning in XenApp 6.5

On the local device, navigate to the local services panel (Control Panel|Administrative Tools) and disable the Windows Image Acquisition (WIA) service. This is done to ensure that the scanner will be using the TWAIN device driver.

Control Panel | Administrative Tools) and disable the Windows Image Acquisition (WIA)

  1. Scan a document locally using the scanner manufacturer’s scanning software to ensure that local scanning functions as expected.
  2. If scanning locally works successfully, log on to the XenApp 6.5 published desktop.
  3. Open a TWAIN-compliant application to see if scanning functions as expected within the XenApp session.
  4. If the application does not see the scanner and scanning within XenApp fails, refer to the following troubleshooting section:

Troubleshooting Information

Desktop Experience Pack

  • For Windows 2008 R2 servers only
  • Some TWAIN devices require the XenApp server to have the Desktop Experience Pack which contains STI.inf, the default INF file for still image devices, as well as the core imaging system binaries including the STI/WIA service and the TWAIN Data Source Manager. To enable this on the server do the following:
  1. Start Server Manager.
  2. In the details pane, locate the Features Summary area, and then click Add Features.
  3. In the Add Features Wizard, click to select the Desktop Experience check box, and then click Next.
  4. Click Install.
  5. After the Desktop Experience feature is installed, click Close to exit the Add Features Wizard, and then click Yes to restart the computer.

TWAIN testing tool

Install Twacker – a third party TWAIN testing tool – to the XenApp server and to the local client device to test TWAIN scanning within a XenApp desktop session.

Download from here.

  1. Install Twacker.
  2. Within a XenApp published desktop session:
  1. Launch Twacker (32-bit version).
  2. Click File > Select Source and select your scanner from the list.
  3. Click File Acquire.
  4. Click the Scan button to test your scanner.

If the Twacker application is able to scan successfully then the XenApp environment is configured properly for USB redirection and to use TWAIN devices, and states all of the requirements have been met on the local client device. In case of further scanning issues within a particular application, it is likely to be a software issue.