Does anyone have a good guide to capabilities of Windows Services under XP? In particular, I am trying to find out what happens when a program being run as a service tries to open windows, but hasn't been given permission to interact with the desktop.
Basically, I have a program that is/was a GUI application, that should be able to run as a service for long term background processing. Rewriting the program to not display the GUI elements when doing background processing is a major effort, so I'd like to see if there is just a way to ignore the UI elements. It is sort of working now, as long as too many windows aren't opened. I'm trying to figure out what limits I might be running into. Ideally, there would be an MSDN page that discusses this, but I've had no luck finding one yet.
Generally, services should be designed to not have any visible UI. The entire point of a service is to run in the background, without UI, unattended. (Think SQL Server, IIS, etc.)
In most scenarios, a separate application controls the service's operation, should a GUI be needed. (Continuing the samples I just mentioned, SQL Server Management Studio, IIS Manager, etc.) These separate applications configure and manipulate the service (and occasionally, if needed, bounce said service).
If your service requires occasional UI, and said UI can't be isolated to a control app, then you probably should reconsider the fact that you're using a service to begin with. Perhaps a UI application which resides in the system notification area is the right pattern to use? (E.G., Windows Live Communicator.)
A service in Microsoft Windows is a program that runs whenever the computer is running the operating system. It does not require a user to be logged on. Services are needed to perform user-independent tasks such as directory replication, process monitoring, or services to other machines on a network, such as support for the Internet HTTP protocol
Usually it is implemented as a console application that runs in the background and performs tasks that don't require user interaction.
The installed services can be configured through the Services applet, available from
Control Panel --> Administrative Tools in Windows 2000/XP.
Services can be configured to start automatically when operating system starts, so you dont have to start each of them manually after a system reboot.
Creating a Simple Service - MSDN Article
Writing Windows Services Made easy - Code Project Article
Five Steps to Writing Windows Services in C - DevX Article
If you should be thinking of eventually migrating to a newer OS such as Vista or Server 2008, you will find that you cannot give a service permission to interact with the desktop at all. Therefore, from the point of view of forwards compatibility, you should design your service to not require it.
A service in Windows XP can interact with the Desktop if its "Allow Service to Interact with Desktop" property (MMC -> service properties -> Log On tab) is checked. It is also possible to do so by doing the following:
hWinstation = OpenWindowStation("winsta0", FALSE, MAXIMUM_ALLOWED);
SetProcessWindowStation(hWinstation);
hDesktop = OpenDesktop("default", 0, FALSE, MAXIMUM_ALLOWED);
SetThreadDesktop(hDesk);
But be aware that presenting UI from a service process in Windows XP will almost always lead to a security problem (see Shatter attack). You should try to break out the UI part of your application from the service.
Usually the service won't have permission to write to the window station and desktop, so it will fail; even running applications that load user32.dll can fail simply because user32 has initialization code that wants to talk to the window station and can't get access to it unless the service is running as an administrator.
Related
I have a rather difficult to manage Windows closed-source Windows GUI application. It's messy (leaves files all over the place) and has a convoluted installation process.
It has been proposed that we containerize the application, but can this be done?
For UNIX applications there's an easy pattern - just give the app access to the port of the X11 server, and allow the app to write to that, but is there a Windows equivalent? Is there any way at all to containerize a Windows application but allow it to generate windows in the host Operating System's desktop?
If this is possible, are there any handy recipes to get started with this?
Currently, It's not possible to containerized Windows GUI application on a windows host.
From the blog Insider preview: Windows container image
Lars Iwer [MSFT] writes in the comments below the article:
"In the container image as it is right now, GUI elements will be rendered in session 0. UI automation should work with that (e.g. programmatically searching for a window etc.)."
So according to my understanding, you can run GUI apps but the rendered elements are not shown on any desktop which will only work for UI automation work but not for user interactive application.
Session 0:
Session 0 is reserved exclusively for services and other non-interactive user applications. Users
who are logged on to Windows and their user applications must run in Session 1 or higher.
- User interfaces in Session 0 are not supported. Processes running in Session 0 have no access to the graphics hardware thus user interfaces cannot be directly displayed on the monitor.
When uninstalling my application, it attempts to stop it if it's running:
Sadly, the automatically closing doesn't really work and it displays this error:
My applications disappear, the windows, the tray bar icon, they are all gone. But I can still see them in the process list.
I'm guessing Windows sends a signal to the applications to exit gracefully and the UI does so, but there's some lingering thread preventing the processes from terminating.
How does Windows Installer close an application during uninstall?
Once I know this I want to simulate it while debugging my app to see what's going on. Is this a sound plan?
Since Windows Vista, Windows Installer will leverage the Restart Manager to identify, close, and restart applications. Microsoft's documentation on Using Restart Manager, and in particular Using Restart Manager with a Primary Installer should be a solid starting point for implementing a test harness. Your applications and services should instead follow the Guidelines for Applications and Services.
The Guidelines for Applications discuss the messages sent to your application by the restart manager; services are restarted through the service control manager. In theory you could simulate the restart manager at that level, but I suspect you'd be better served by invoking the real thing, registering a carefully chosen list of resources to target just your application, if possible.
I'm looking to determine if our application is running on a XenDesktop session rather than locally. Here is what I have found so far:
We currently have code to detect a Citrix XenApp session similar to the solution mentioned by Helge Klein in "API for Determining if App is Running on Citrix or Terminal Services".
Sadly that solution in a XenDesktop environment is returning back a WTSClientProtocolType of 0 which signifies a local console session.
In response to the same question Josh Weatherly mentioned checking the sessionname environment variable.
However a quick console check with echo %sessionname% on the XenDesktop environment returns back 'Console'.
From "Detect citrix “application mode”?" John Sibly suggested a solution for detecting a remote session (not Citrix in particular):
GetSystemMetrics(SM_REMOTESESSION) however returns 0 which also means that it is a local session.
Does anyone know of a way to detect that it is a XenDesktop session? So far as you can see all my attempts are returning that the session is a local console session.
I'm using XenDesktop Express 5.5, accessing the desktop using the Citrix Receiver Web Plug-In.
If you are using XenDesktop for VDI, then as far as the application is concerned, the application is executing locally. VDI, or virtual desktop infrastructure, consists of delivering the GUI from a full featured desktop operating system to a remote device. Typically, the desktop O/S executes in a virtual machine on a hypervisor in a data center, and the GUI is transmitted to the remote device using Citrix' ICA stack. For example, this happens in the pooled desktops scenario.
XenApp offers virtual desktops, which is a slightly different concept. Again, the desktop is delivered to a remote device using the ICA stack. However, the desktop is no longer running on a dedicated O/S. Rather, it is one of a number of user sessions on a single Windows Server. There may be any number of users logged on to that server. This places limits on the applications that can be run, which is why applications might want to know that they are on a multi-user O/S.
What you might try to do is determine whether the GUI is being delivered remotely using the ICA stack. A simple check would involve looking for the "ProticaService", which is responsible for implementing the ICA stack.
Alternatively, you may be trying to determine if your machine is running in a VM or native to a machine. Besides the pooled scenario described in the first paragraph, XenDesktop can deliver desktop running native. This overcomes limits on virtualision I/O devices such as graphics cards used by CAD applications. In this case, you need to rule out the presence of a VMM, or hypervisor.
I have updated my answer linked to in the question with a description of how to determine the remoting protocol type in XenDesktop sessions.
You need the (not really well documented) function WFGetActiveProtocol from Citrix' WFAPI SDK. Proceed as follows:
Download the SDK (link)
Install WFApiSDK64-65.msi
In your C++ project include wfapi.h and link to wfapi[64].lib
Use the undocumented function WFGetActiveProtocol
More detail and sample code here.
I need a background application to support my client application, which should always run on the client machine regardless of the main client application is running or not.
Windows Service was my first choice but problems I faced with Windows Service were: ease of control over windows service through main client application, release and installation of patches to the windows service and troubleshooting if windows service fails to run.
So, I started thinking for alternatives to the Windows Service and found that a Windows Forms application with NO visible forms can do it for me. This invisible app should start with system startup and keep running all the time, doing all the work that a Windows Service would do. But before I go deeper into the development, I want to explore the pros and cons of this approach.
Any suggestions/comments on this approach?
Your requirements are more suited for windows service. Main advantage with windows service is that it will start as soon as system comes up, irrespective of anybody is logged into system or not.
To sort out deployment issues, you build your business logic into separate assembly and call the necessary function withing windows service. This way you can deploy just the modified assembly.
Winform application with invisible form will not serve the purpose. HTH
That's not possible. User-mode applications must be started by a user, and will not continue to run when that user logs off. That's the purpose of the SessionEnding event: to allow you to shut down your app gracefully when the user logs off or the computer is shutting down. You can't just start something at system startup and keep it running all the time.
You need a Windows Service for that. But you should be aware that under Windows Vista and later, a service cannot interact directly with the user. They run in a separate process and are restricted from displaying their own UI. It's not clear from the question exactly what your needs are, but this is an important limitation of a Windows Service that is worth considering. A proper design really shouldn't require this, but there are apparently a lot of people to whom this new, more secure behavior is a real surprise. I explain this in more detail in related answers to this question and this other question.
I have installed cc.net 1.4.3 version on Windows Vista. But It keeps giving me Interactive services dialog detection when I execute tests. I even have disabled the interactive services from services panel. but still getting this.
Any idea how to get rid of this problem
regards
Sam
No easy fix that you can do. The service is trying to pop up UI on the user desktop. In XP this worked because services and the first user log on both run in session 0. In Vista, services run in session 0 and the first user runs in session 1, so there is no way for a service to directly show UI to the user. This was due to security issues - search for Win32 Shatter Attack to get more details, but basically an untrusted user could send malformed window messages to the services, and in some cases could even cause arbitrary code execution.
You can disable it altogether by disabling the "Interactive Services Detection" service on the system. But you won't see notifications at all, and this will disable it for all interactive services. Best approach is to complain to the vendor to update their software for Vista.
EDIT: And the software is broken on XP when multiple users are logged on and the active user isn't in session 0.