Citrix PS 4 Cannot connect to the Citrix XenApp server. Protocol Driver error

Posted on 2012-08-28
Last Modified: 2013-06-16
Guys, I have Citrix PS 4 (yeah still using it ) on Windows 2003. Few weeks ago I had maintenance on all of our servers apply MS Windows security updates.

After the updates were applied no problem but after the scheduled reboot of Citrix users are getting "I am unable to open citrix, I get the following error message: Unable to launch your application. Contact your help desk with the following information: Cannot connect to the Citrix XenApp server. Protocol Driver error"

I had to redo some of the security permission for Ctx_SmaUser and follow the steps from the link below to reset the ICA 3.0 to use a specific NIC. Reboot after these changes and it worked fine - reboot again and I get the same protocol error above again. Reboot few more and it work fine without any change. Changing the ICA to use the server NIC or use all NIC doesn't seem to make a difference here.

Since then I have deleted the old Citrix ICA and created new ICA but still the same problem after a reboot. I did noticed that in the registry the old deleted ICA was created under the Console section vs new ICA under WinStations (pic attached) - just FYI.

Assigning ICA-tcp properties to a specific network adapter - not working


Thanks much.
Question by:Symbian69
    LVL 36

    Expert Comment

    by:Carl Webster
    I have had that issue at several customers and the underlying cause was unexpected.

    Worth a look at.
    LVL 7

    Accepted Solution

    This is a known issue where your ICA_TCP listener get crashed after every reboot of the system .

    Please reset your ICA listener and you should be good to go . for permanent fix you need to apply the below listed hotfix:

    to reset ICA listener in the server use the below command in the server with admin credential:

    reset session ica-tcp /server:SERVER1

    ** replace SERVER1 with the hostname of the server

    or run TSADMIN , from terminal server manager on the right side select ICA-tcp, right click and reset, it should be in listening mode. During the issue I am expecting that to be in Down mode.

    for permanent fix apply the below hotfix:


    Author Comment

    Thanks much. I'll schedule another maintenance and try the hotfix.

    Author Closing Comment

    Thanks much  sarmahjay! I applied this hotfix once I was able to schedule a maintenance and seem to have fixed the ica crashing after a reboot. <br /><br />Thanks again.

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