Remko Weijnen's Blog (Remko's Blog)

About Virtualization, VDI, SBC, Application Compatibility and anything else I feel like

Archive for the ‘Vista’ Category

Vista SP1 changes to Terminal Server API

In a previous article I wrote about changes in utildll in vista that breaked compatibality for Terminal Server. Even though release notes for Service Pack 1 don’t indicate changes or fixes in this area my testing shows that Microsoft has taken over the Windows 2008 implementation of utildll to Vista.

This is a good thing, because applications depending on utildll work again. I have updated JwaWinsta for SP1, all Vista versions of the utildll functions are renamed to VistaRTM and all Safe functions were updated to check for SP1. This means that the Safe functions can be used on all OS versions and Service packs! You are strongly advised to use only the Safe functions.

Some observations with SP1: 

  • I quickly tested TSAdmin as well and it seems to work again, only noticable flaw is that the console sessions returns an idle time of 17642 days (Reported Last Input Time is 01-01-1601 but utildll’s ElapsedTimeString function doesn’t account for dates this long in the past).
  • WTSApi32.dll contains some new functions like WTSStartRemoteControlSession and WTSStopRemoteControlSession (which are wrappers to WinStationShadow).
  • The WTSWaitSystemEvent bug I wrote about earlier is still present. I advise to check for winsta.dll version >= 6.0.6000.20664 in code when using this API and advise user to install the Hotfix.

Update: I just tried to install hotfix KB941561 but this fail with the error: The update does not apply to your system. If you do want to get this bug fixed you need to manually replace winsta.dll (take ownership and set permissions to full control). winsta.dll from hotfix KB941561 (X86) (2570 downloads)

TSAdminEx Progress

I just wanted to show some of the progress that I made in development of TSAdminEx. I thought the best way would be to show some screenshots. Which reminds me I installed a nice Javascript to enlarge the thumbnails, click to see it…

Edit: A beta is ready!

This screenshot shows TSAdminEx after startup. In the Left Treeview you can see the This Computer, Favorites and All Listed Servers icon. On Startup all available domains are enumerated.
Here you see the Users tab. If you move the mouse over some columns you can get extra info in the hint. In this hint you get the actual shadow permissions of the highlighted session.
This is the Sessions tab where extra details of a session are shown. By default you can see sessions statistics such as Incomingbytes and Outgoingbytes, this makes it easy to identify sessions that have much traffic.Interesting detail is that the Remote Address column lists the real ip address that is connected to Terminal Server! Hovering the mouse also shows the port number.
Now the Process tab is my favorite! It lists far more details than TSAdmin and also some usefull columns that cannot be show with TSAdmin or any documented Terminal Server API!The Process Age columns shows how long the process is running. You can compare this with the CPU Time column to see how much CPU Time the process has allocated since startup.The Mem Usage shows the amount of physical RAM a process uses while the VM Size column shows the amount of Private Bytes (Virtual Memory) a process uses.
If you click on a domain in the Left Treeview, TSAdminEx will enumerate all Terminal Servers for that domain. You can continue using and even enumerate multiple domains, because enumeration is done from seperate threads!
If you select (highlight) a particular session the appropriate toolbar buttons are enabled or disabled automically indicating the actions that can be performed on the selected session.
And offcourse, an about dialog…

Hope you like it! Comments are open…

Using WTSWaitSystemEvent

If you develop an application for Terminal Server you might want to react on session events. This means that your application is notified when a user logs on, logs off or becomes idle. This can be done with the WTSWaitSystemEvent function. Implementing it is rather simple and could look something like this:

Notice that you would probably do this from a seperate thread otherwise you will block the main thread. To stop waiting for Events you send a special event:

Please note that there are at least 2 issues with this API, one with Windows 2000 and one with Windows Vista. On Windows 2000 events are reported twice for each actual event. Microsoft’s resolution?

The application should expect the event twice, and filter out the second occurrence.

Now how do we solve this? I would suggest introducing a small delay after an event trigger, this way you will probably not receive the duplicate event.

On Windows Vista there’s another issue: After you set the value of the EventMask parameter to WTS_EVENT_FLUSH in the WTSWaitSystemEvent function, no pending calls to the function return on a Windows Vista-based computer. Now what does this mean? It means that after sending WTS_EVENT_FLUSH the thread never responds! So there’s actually no nice way to end the thread, the only escape is a call to TerminateThread.

Microsoft does offer a hotfix, so my suggestion is a check on startup that will notify the user that he/she needs to install the hotfix. A version check can be done on winsta.dll, the version before the fix is 6.0.6000.16386. Hotfix version is 6.0.6000.20664. According to this article the fix will be included in Vista SP1.


Why TSAdmin crashes on Windows Vista

Have you ever tried running the Terminal Server Administration tool (aka TSAdmin) on Windows Vista? You would need it to remotely administer windows 2000/2003 Terminal Servers. If you try to run it you will get an Access Violation but why? I found the answer to this question today because I was testing my TSAdmin replacement on different Windows versions. Just like TSAdmin I use an (undocumented) function from Utildll.dll called ElapsedTimeString. It’s a very simple function that returns a formatted elapsed time string (as seen in the Idle time column from TSAdmin).

While my TSAdminEx ran fine on Windows XP, 2003 and even 2008 it would crash on Vista. Investigation showed that the stack was corrupted in the process of enumerating processes and sessions. Eventually I pinned it down to ElapsedTimeString but could not understand what went wrong. At least not until I investigated Utildll.dll version from Windows Vista. In what was probably an attempt from Microsoft to produce safer code they replaced wsprintfW by StringCchPrintfW. But StringCchPrintfW has an additional parameter (count of characters) so they introduced a new parameter to ElapsedTimeString. Now that’s not a smart decision as this directly breaks compatibility with software that uses this API, but they probably thought that it wasn’t issue since TSAdmin is not included with Vista (I don’t know of any other MS tool that uses this API).

But why doesn’t the Access Violation appear on Server 2008? Is this still using wsprintfW for string formatting? The answer is no, they also use StringCchPrintfW but use a fixed 15 character length. (so they “fixed” the issue).

That leaves you with 2 options if you still want to use TSAdmin on Vista:

  1. Patch TSAdmin or Utildll
  2. Use my TSAdminEx instead which also offers some extra functionality over TSAdmin (I hope to finish it soon, should you wish to beta test then leave a comment).

For now I’ll leave you with a screenshot (click to enlarge) of the current Beta version. As you can see it returns detailed information in the process tab like Memory Usage, Virtual Memory Usage, CPU Time and Process Age.

TSAdminEx Beta Screenshot

Multiple Terminal Sessions in Windows Vista

There were 2 ways (known to me) of extending Windows XP to offer mulitple concurrent Terminal Sessions. One with the RC1 version of XP SP2 and one that patches Winlogon and Termsrv.dll. The latter offers not only multiple sessions but also multiple sessions under the same account and sessions to the local machine.

Seems like the someone hacked Windows Vista Terminal server too by patching Termsrv.dll. Read more at source.

New Terminal Server API’s in Vista SP1

The upcoming Vista SP1 promises 3 new Terminal Server API functions:

If you look in the Windows 2008 beta you can see that the functions are already implemented (in WtsApi32.dll):


Atheros AR5007EG – Bad WLAN performance

A friend bought a new Toshiba Satellite L40 laptop which came with Windows Vista preinstalled. The wireless connection (via the built in Atheros AR5007EG card) was very unstable and sometimes unable to connect to the access point. When connected internet speed was very slow, sometimes unable to open pages at all. First we tried replacing the preinstalled Toshiba drivers with the latest from the Toshiba site and later on the most recent from Atheros (which can be found here).  Both drivers didn’t improve the speed.  


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