Introduction
Typically, an NT service is a console application, which does not have
a message pump. An NT Service can be started without the user having to
login to the computer and it won't die after the user logs off. However,
it is hard, sometimes impossible, to use many existing ActiveX controls
within a console application.
On the other hand, MFC and VB applications are Windows applications, so
using ActiveX controls in MFC or VB programs is extremely easy. It would
be nice to make your MFC and VB programs run like an NT service so that:
- They will be started before the user logs into the computer.
- They will keep running after the user has logged off.
It is possible to write an NT service as a Windows program but I am
proposing a much easier solution. I have included with this article the
source code for a simple NT Service program that can start and shutdown
other programs. All you need to do is install this service and modify a
.ini file. Here are the advantages of using this simple NT
service:
- It can start as many programs as you want. The started programs
behave like NT services (i.e. they will be running in the background
without the user having to login to the machine).
- A user cannot kill the programs started by this service without
proper privilege (unless the machine is shutdown, of course).
- You can test and debug your programs outside of the NT Service. For
example, you can run your programs in the DevStudio debugger, step into
the source code to find the bugs, etc. When it is "bug free", you deploy
it in production, starting it from the NT Service.
XYNTService
XYNTService.exe is the name of the executable for this NT
service program. It is part of a client-server
development tool I invented. You can freely use and modify the source
code included with this article. I am now aware that there are other
utility programs that provide almost the same functionality as
XYNTService. However, as you will see, XYNTService has more features and
it is a lot easier to use (no editing of the registry is required, for
example). Here is how to use the program.
- To install the service, run the following at the command prompt:
XYNTService -i
- To un-install the service, run the following at the command prompt:
XYNTService -u
By default, the installed service will be started automatically when
you reboot the computer. You can also start and shutdown the service from
the Control Panel using the Services icon. When the service is
started, it will create all the processes you defined in the
XYNTService.ini file one by one. When the service is shutdown, it
will terminate each of the processes it created (in reverse order). The
XYNTService.ini file should be placed in the same directory as the
executable. Here is a sample of the file:
[Settings]
ServiceName = XYNTService
ProcCount = 3
CheckProcess = 30
[Process0]
CommandLine = c:\MyDir\XYRoot.exe
WorkingDir = c:\MyDir
PauseStart = 1000
PauseEnd = 1000
UserInterface = Yes
Restart = Yes
[Process1]
CommandLine = c:\MyDir\XYDataManager.exe
WorkingDir = c:\MyDir
PauseStart = 1000
PauseEnd = 1000
UserInterface = Yes
Restart = Yes
[Process2]
CommandLine= java XYRoot.XYRoot XYRootJava.ini
UserInterface = No
Restart = No
The ServiceName property specifies the name you want to
use for this NT service, the default name is XYNTService. If
you copy the executable and the .ini file into a different
directory and modify the ServiceName property in the
.ini file, then you can install and configure a different
service!
The ProcCount property specifies how many processes you
want this service to create. The sections [Process0], [Process1], ..., etc., define
properties related to each of these processes. As you can see, there are 3
processes to create in this example, XYRoot.exe ,
XYDataManager, and java are the names of the programs, and
you can specify parameters for each of these processes in the
CommandLine property. You must specify the full path
of the executable file for the corresponding process in the
CommandLine property unless the executable is already in the
system path.
The CheckProcess property specifies whether and how often
you want to check processes started by XYNTService. If the property has
value 0, then no checking is done. If the property value is 30, for
example, then every 30 minutes XYNTService will query the operating system
to see if the processes it started are still running and the dead ones
will be restarted if the Restart property value (explained
later) is defined to be Yes for that process. The default
value of this property (if you don't specify it) is 60.
The WorkingDir property is the working directory of the
current process. If you don't specify this property, then the working
directory of the current process will be c:\winnt\system32. The
PauseStart property is the number of milliseconds the service
will wait after starting the current process (and before starting the next
process). This is useful in the case where the next process depends on the
previous process. For example, the second process has to "connect" to the
first process so that it should not be run until the first process is
finished with initialization. If you don't specify the
PauseStart property, the default value will be 100
milliseconds.
When XYNTService is shutdown, it will post WM_QUIT
messages to the processes it created first and then call the WIN32
function TerminateProcess. The PauseEnd property
is the number of milliseconds the service will wait before
TerminateProcess is called. This property can be used to give
a process (started by XYNTService) a chance to clean up and shutdown
itself. If you don't specify the PauseEnd property, the
default value will be 100 milliseconds.
The UserInterface property controls whether a logged on
user can see the processes created by XYNTService. However, this only
works when XYNTService is running under the local system account, which is
the default. In this case, processes created by XYNTService will not be
able to access a specific user's settings (e-mail profiles, etc.). You can
configure XYNTService to run under a user account, which is done easily
from the Control Panel (double click the Services icon and then
double click XYNTService in the installed services list to bring up a
dialog box).
The Restart property is used to decided whether you want
XYNTService to restart a dead process. If this property is No
(which is the default if you don't specify it), then the corresponding
process will not be restarted. If this property is Yes, then
the dead process will be restarted by XYNTService. See the
CheckProcess property above on how often dead processes are
restarted.
You can bounce (stop and restart) any process defined in the
.ini file from the command line. For example, the following
command:
XYNTService -b 2
will stop and restart the process defined in the
[Process2] section of the .ini file.
XYNTService can also be used to start and stop other services from the
command line. Here are the commands to start (run) and stop (kill) other
services.
XYNTService -r NameOfServiceToRun
XYNTService -k NameOfServiceToKill
In particular, you can use the above commands to start and stop
XYNTService itself from command line! Please note that you cannot start
XYNTService by running it from the command prompt without any argument.
All errors while running XYNTService are written into a log file in the
same directory as the executable. The error code in the log file is a
decimal number returned by the GetLastError API, you can look
it up in MSDN.
Latest Updates
A new feature is added so that XYNTService can check the processes it
started periodically. A dead process will be restarted by XYNTService if
you specify the Restart property for this process in the
XYNTService.ini file.
The author would like to thank user WolfSupernova for finding a
bug in the code that will prevent XYNTService from terminating the
programs defined in XYNTService.ini when the machine is
rebooted.
Frequently Asked Questions
- Why can't XYNTService start my program? There could be many
reasons. The likely ones are, you did not give the correct path of the
executable in the XYNTService.ini file or your program is located
on a mapped network drive (see the following question).
- My program works fine outside of XYNTService, why does it fail
when started by XYNTService? XYNTService is running under the "local
system" account by default, any program started by it will also use this
account. Your program may need some resource that is not available to
this account. For example, "local system" cannot access the current
user's registry settings, nor can it access a mapped network drive or
any other resource on the LAN. However, you can change the account used
by XYNTService, this topic is covered by the question below.
- How do I change the account XYNTService uses? On Windows
2000, use the "Adminstrative Tools" menu, select "Services" and then
double click XYNTService from the displayed list to change the logon
information (domain name, user name and password). On Windows NT 4.0,
use the Control Panel, select/open the Services icon, then double click
XYNTService from the displayed list to change the logon information.
Please note that you cannot see your program started by XYNTService if
XYNTService is not using the "local system" account.
- How to run my program as a service? You can't, unless you
rewrite your program from scratch. A service is a special program which
requires some special knowledge to write. If you don't want to learn how
to write a service, then use XYNTService to start your program as
described in the article so that your program behaves like a service.
- How do I debug a service? First, build your service program
in debug mode from Visual Studio, setting break points if necessary.
Then install and start the service. Finally, attach the debugger to the
service executable (that is already running). Note that a service has to
be started before the process can be attached to the debugger, so some
parts of it can never be stepped into (from the debugger). In fact, most
useful code in XYNTService cannot be debugged because the code is
executed while XYNTService is starting.
- Why my Java program won't run under XYNTService or dies when user
logs off the machine? This could be caused by a bug in Java itself,
I think. I had some problems with recent versions of JDK, but not with
JDK 1.2.2. If you cannot use JDK 1.2.2, then try the Xrs option
when using Java and also change the account used by XYNTService to a
domain user instead of the default "local system" account. This may help
you to get around the problem.
