Title: Example of a Windows Service, with a thread
Question: Delphi 5 and up has a template project for services, but it is incomplete. This example builds on that template and completes the service. It also shows how to start a thread that beeps every 2 seconds. You can use this as a base when developing services.
Answer:
This example shows how to use the service template in delphi, taking it a step further and making a complete example. The source for this is included in the ntservice.zip file.
Coded under D6, but works for D5 if you copy the source parts after creating a template service.
Below are all the source files listed one by one. The same files and the whole project is in the NTService.zip file (as soon as it is uploaded)
To test the source, create a Service with Delphi, and pase these sources
on top of the automatically generated source.
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program NTService;
uses
SvcMgr,
NTServiceMain in 'Units\NTServiceMain.pas' {ExampleService: TService},
NTServiceThread in 'Units\NTServiceThread.pas';
{$R *.RES}
begin
Application.Initialize;
Application.CreateForm(TExampleService, ExampleService);
Application.Run;
end.
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(*
Windows Service Template
========================
Author Kim Sandell
Email kim.sandell@celarius.com
Disclaimer Freeware. Use and abuse at your own risk.
Description A Windows NT Service skeleton with a thread.
Works in WinNT 4.0, Win 2K, and Win XP Pro
The NTServiceThread.pas contains the actual
thread that is started under the service.
When you want to code a service, put the code in
its Execute() method.
Example To test the service, install it into the SCM with
the InstallService.bat file. The go to the Service
Control Manager and start the service.
The Interval can be set to execute the Example
Beeping every x seconds. It depends on the
application if it needs a inerval or not.
Notes This example has the service startup options set to
MANUAL. If you want to make a service that starts
automatically with windows then you need to
change this.
BE CAREFULT ! If your application hangs when
running as a service THERE IS NO WAY to
terminate the application.
History Description
========== =====================================================
24.09.2002 Initial version
*)
unit NTServiceMain;
interface
uses
Windows, Messages, SysUtils, Classes, SvcMgr,
NTServiceThread;
type
TExampleService = class(TService)
procedure ServiceExecute(Sender: TService);
procedure ServiceStart(Sender: TService; var Started: Boolean);
procedure ServiceStop(Sender: TService; var Stopped: Boolean);
procedure ServicePause(Sender: TService; var Paused: Boolean);
procedure ServiceContinue(Sender: TService; var Continued: Boolean);
procedure ServiceShutdown(Sender: TService);
private
{ Private declarations }
fServicePri : Integer;
fThreadPri : Integer;
{ Internal Start & Stop methods }
Function _StartThread( ThreadPri:Integer ): Boolean;
Function _StopThread: Boolean;
public
{ Public declarations }
NTServiceThread : TNTServiceThread;
function GetServiceController: TServiceController; override;
end;
var
ExampleService: TExampleService;
implementation
{$R *.DFM}
procedure ServiceController(CtrlCode: DWord); stdcall;
begin
ExampleService.Controller(CtrlCode);
end;
function TExampleService.GetServiceController: TServiceController;
begin
Result := ServiceController;
end;
procedure TExampleService.ServiceExecute(Sender: TService);
begin
{ Loop while service is active in SCM }
While NOT Terminated do
Begin
{ Process Service Requests }
ServiceThread.ProcessRequests( False );
{ Allow system some time }
Sleep(1);
End;
end;
procedure TExampleService.ServiceStart(Sender: TService; var Started: Boolean);
begin
{ Default Values }
Started := False;
fServicePri := NORMAL_PRIORITY_CLASS;
fThreadPri := Integer(tpLower);
{ Set the Service Priority }
Case fServicePri of
0 : SetPriorityClass( GetCurrentProcess, IDLE_PRIORITY_CLASS );
1 : SetPriorityClass( GetCurrentProcess, NORMAL_PRIORITY_CLASS );
2 : SetPriorityClass( GetCurrentProcess, HIGH_PRIORITY_CLASS );
3 : SetPriorityClass( GetCurrentProcess, REALTIME_PRIORITY_CLASS );
End;
{ Attempt to start the thread, if it fails free it }
If _StartThread( fThreadPri ) then
Begin
{ Signal success back }
Started := True;
End Else
Begin
{ Signal Error back }
Started := False;
{ Stop all activity }
_StopThread;
End;
end;
procedure TExampleService.ServiceStop(Sender: TService;
var Stopped: Boolean);
begin
{ Try to stop the thread - signal results back }
Stopped := _StopThread;
end;
procedure TExampleService.ServicePause(Sender: TService; var Paused: Boolean);
begin
{ Attempt to PAUSE the thread }
If Assigned(NTServiceThread) AND (NOT NTServiceThread.Suspended) then
Begin
{ Suspend the thread }
NTServiceThread.Suspend;
{ Return results }
Paused := (NTServiceThread.Suspended = True);
End Else Paused := False;
end;
procedure TExampleService.ServiceContinue(Sender: TService;
var Continued: Boolean);
begin
{ Attempt to RESUME the thread }
If Assigned(NTServiceThread) AND (NTServiceThread.Suspended) then
BEGIN
{ Suspend the thread }
If NTServiceThread.Suspended then NTServiceThread.Resume;
{ Return results }
Continued := (NTServiceThread.Suspended = False);
END Else Continued := False;
end;
procedure TExampleService.ServiceShutdown(Sender: TService);
begin
{ Attempt to STOP (Terminate) the thread }
_StopThread;
end;
function TExampleService._StartThread( ThreadPri: Integer ): Boolean;
begin
{ Default result }
Result := False;
{ Create Thread and Set Default Values }
If NOT Assigned(NTServiceThread) then
Try
{ Create the Thread object }
NTServiceThread := TNTServiceThread.Create( True );
{ Set the Thread Priority }
Case ThreadPri of
0 : NTServiceThread.Priority := tpIdle;
1 : NTServiceThread.Priority := tpLowest;
2 : NTServiceThread.Priority := tpLower;
3 : NTServiceThread.Priority := tpNormal;
4 : NTServiceThread.Priority := tpHigher;
5 : NTServiceThread.Priority := tpHighest;
End;
{ Set the Execution Interval of the Thread }
NTServiceThread.Interval := 2;
{ Start the Thread }
NTServiceThread.Resume;
{ Return success }
If NOT NTServiceThread.Suspended then Result := True;
Except
On E:Exception do ; // TODO: Exception Logging
End;
end;
function TExampleService._StopThread: Boolean;
begin
{ Default result }
Result := False;
{ Stop and Free Thread }
If Assigned(NTServiceThread) then
Try
{ Terminate thread }
NTServiceThread.Terminate;
{ If it is suspended - Restart it }
If NTServiceThread.Suspended then NTServiceThread.Resume;
{ Wait for it to finish }
NTServiceThread.WaitFor;
{ Free & NIL it }
NTServiceThread.Free;
NTServiceThread := NIL;
{ Return results }
Result := True;
Except
On E:Exception do ; // TODO: Exception Logging
End Else
Begin
{ Return success - Nothing was ever started ! }
Result := True;
End;
end;
end.
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(*
A Windows NT Service Thread
===========================
Author Kim Sandell
*)
unit NTServiceThread;
interface
uses
Windows, Messages, SysUtils, Classes;
type
TNTServiceThread = Class(TThread)
private
{ Private declarations }
Public
{ Public declarations }
Interval : Integer;
Procedure Execute; Override;
Published
{ Published declarations }
End;
implementation
{ TNTServiceThread }
procedure TNTServiceThread.Execute;
Var
TimeOut : Integer;
begin
{ Do NOT free on termination - The Serivce frees the Thread }
FreeOnTerminate := False;
{ Set Interval }
TimeOut := Interval * 4;
{ Main Loop }
Try
While Not Terminated do
Begin
{ Decrement timeout }
Dec( TimeOut );
If (TimeOut=0) then
Begin
{ Reset timer }
TimeOut := Interval * 4;
{ Beep once per x seconds }
Beep;
End;
{ Wait 1/4th of a second }
Sleep(250);
End;
Except
On E:Exception do ; // TODO: Exception logging...
End;
{ Terminate the Thread - This signals Terminated=True }
Terminate;
end;
end.
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