Internet Access: Client Service

So far we have looked at what a service is and how it works. Now we will write the code to make our service active. Before we write the code, let's look at what we want our service to do.

Basically we want it to see if the client application is running. If it is not, then we want it to start the application, otherwise we want it to do nothing. The service must check every couple of seconds or minutes (depending on your choice) to see if the client application is active.

Below is the entire service application code. Note that I’ve now saved the unit as “icstarter.” I’ve also added a timer component. The following properties are set:

Displayname: iCafeService

Servicetype: stWin32

Starttype: stAuto

Interactive: True (for debugging purposes)

unit icstarter;

interface

uses

Windows, Messages, SysUtils, Classes, Graphics, Controls, SvcMgr, Dialogs,

ExtCtrls,shellapi;

type

TService1 = class(TService)

Timer1: TTimer;

procedure Timer1Timer(Sender: TObject);

procedure ServiceExecute(Sender: TService);

private

{ Private declarations }

public

function GetServiceController: TServiceController; override;

{ Public declarations }

end;

var

Service1: TService1;

implementation

{$R *.DFM}

procedure ServiceController(CtrlCode: DWord); stdcall;

begin

Service1.Controller(CtrlCode);

end;

function TService1.GetServiceController: TServiceController;

begin

Result := ServiceController;

end;

procedure TService1.ServiceExecute(Sender: TService);

begin

//activate the client application here

timer1.Enabled:=true;

while not terminated do

servicethread.ProcessRequests(true);

timer1.Enabled:=false;

end;

procedure TService1.Timer1Timer(Sender: TObject);

var

handle,h: HWND;

begin

handle:= FindWindow('TForm1', 'iClient');

if handle > 0 then

begin

showmessage('found it!');

end

else

begin

//startup the app here. Shellexec

shellexecute(h,'open','c:\intertimer\client\iclient.exe',nil,nil,0);

end;

end;

end.