Thursday, 2 December 2010

Shadowing in XenApp 6

The ability of an administrator or helpdesk to shadow their users is about as basic as it gets – a system like XenApp used to distribute applications remotely is unlikely to be serving a group of people in one room.  Yet bizarrely this feature, hardly recent addition to Citrix’s offering, has had quite profound problems in XenApp 6.

Broadly, there are a couple of issues.  The first is the Citrix client – versions 11.2 and 12.0 of the online plug-in had serious problems regarding shadowing which have only just been fixed in v12.1, which I am now recommending for anyone who might shadow a user.  The second is the heady technology that is having two monitors.  Basically, it would appear shadowing was only ever tested on machines with a single monitor – either that or Citrix released XenApp 6 knowing it had a major broken feature.

In my initial test environment when I started evaluating XenApp 6 I was using the v11.2 client on a pair of PCs with two monitors each so you can understand my initial estimate was the shadowing was in fact completely impossible.

The Client bug

The v11.2 and v12.0 online plug-ins do appear to support shadowing – mostly.  But when it connects it often only displays part of the user’s screen, with the image clipped at the sides and no way of scrolling, and sometimes it just closes immediately with an Error 120 messagebox.  This was not limited to XenApp 6, I had it on an old Presentation Server 4.0 farm. Apparently there was a workaround to publish the admin console as a non-seamless application, though the v11.0 client usually worked and the new 12.1 client does too. 

Basically, upgrade the helpdesk users to 12.1 and the clipping issue should go away.

The Dual Monitors bug

Ah, the biggie.  Basically, if the user being shadowed OR the user doing the shadowing has more than one monitor, you cannot shadow their seamless applications.  Pretty basic, really. 

Shadowing from a PC with one monitor to one with two gives the useful error “Error 7044 – The request to control another session remotely was denied”:


This sounds like an access issue, but it isn’t.  Its been denied because its not possible.  If you shadow from a PC with two monitors to one with a single monitor you get the real error - “Error 120 – this function is not supported on this system”.  Because it isn’t.


I’ve raised this with Citrix – they say its a Microsoft issue with shadowing on 2008 R2.  I build a Server 2008 R2 Remote Desktop Services server hosting seamless applications through a web interface and it does indeed do exactly the same thing – sessions started on a PC with two monitors cannot be Remotely Controlled – you get told “Access is denied”.


imageNice. So I raise it with Microsoft Support who say this is “by design”, not a bug.  Though it might be “redesigned” in the future.  Its actually easy to fix on RDS:

  • On each RDS server, open “Remote Desktop Session Host Configuration”
  • Right click RDP-Tcp, select Properties
  • Select Client Settings
  • Change the maximum number of monitors to 1. 

Not much good if you specifically want a two monitor Terminal Services session, but it will work for seamless apps.  Anyway, the same fix does nothing for XenApp I’m afraid.

Enough of this nonsense.  These workarounds suggest themselves for XenApp 6 which will get shadowing possible in most cases:

  1. Make sure your admin people have the v12.1 online plug-in
  2. Publish your XenApp management tools as a Desktop, or even better as a non-seamless application.  This will get around problems caused by your helpdesk and admin staff having two monitors.  You can see instructions on how to force a single published application to be “windowed” rather than seamless here:  But basically you edit the conf\default.ica file in each site on your web interface box to include some extra lines, starting with the name of the published app in square brackets, such as:

    [XenApp Console]
  3. If a dual monitor user calls up and asks to be shadowed, tell them to close their Citrix applications, disable all but one monitor and launch them again!  Just kidding, though that would work…
  4. Ask said user to launch a published desktop which you have configured to be of a specific size – say 1024x768 or 90%.  If this has a Citrix client in it, they can launch apps there and you will be able to shadow the desktop and see its contents.
  5. Alternatively, get them to temporarily change their client to open all apps in a specific window size rather than seamless.  So, if they use the online plug-in, right click its icon, select Options, Session Options and select a Window Size:
    …or if they use the Web Interface, get them to go to Preferences, Session Settings and select the Window Size there instead:


The next session they start you should be able to shadow. 

This is, of course, all a bit rubbish.  Hopefully it will get fixed soon, whether its a Citrix or Microsoft fix.

UPDATE 20/05/2011

Thanks for the comments below – I had meant to update this entry anyway.  We did make some progress on this, though it wasn’t great.  We found that indeed Remote Assistance works fine, so have been using it on clients with two monitors.  We also found that the v12.0 client was rubbish for this as well (the XenApp sessions work initially when shadowed but then start flashing dramatically – this is fixed with a v12.1 upgrade).  At least the users could be shadowed, at least the ones on the network could.  Not much use for someone on a remote PC not on our LAN though.

The comment below about using Remote Assistance to the server session is interesting though.  I’m off to experiment now…


Kipp said...

Have you seen any progress on this issue?

Josh Mueller said...

I have a work around using Remote Assistence here:


Anonymous said...

Hello thx for this blog.

i have done the Installation but i
can't logon
qfarm load is 100 and i don't know how to solve this Problem.

Anonymous said...

Hi - well.. I have this error when starting citrix shadow bar

Chiraag said...

Nice, I like the fix using default.ica on the web interface servers.

Anonymous said...

Perfect. Thank you, its worked a treat! :0)

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