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<p class=Code><span class=Code> </span></p>
<p class=Code><span class=Code><b>void</b> <b
style='mso-bidi-font-weight:normal'>__fastcall</b> TBeepServiceThread::BeepServiceThreadContinue(</span></p>
<p class=Code><span class=Code> TService *Sender, <b>bool</b> &Continued) </span></p>
<p class=Code><span class=Code>{</span></p>
<p class=Code><span class=Code> BeepThread->Resume();</span></p>
<p class=Code><span class=Code> Continued = <b>true</b>;</span></p>
<p class=Code><span class=Code>}</span></p>
<p class=Captions><b>Figure
7:</b> The <i
style='mso-bidi-font-style:normal'>OnPause</i> and <i>OnContinue</i> event handlers. </p>
<p class=BodyText> </p>
<p class=BodyText> Notice
that I set the <i>Paused</i> parameter to <b>true</b>
in the <i>OnPause</i> event handler after I
suspended the thread. If I don't set <i>Paused</i>
to <b>true</b>, Windows can't pause the thread. You may want to set <i
style='mso-bidi-font-style:normal'>Paused</i> to <b>false</b> if your service
is in a state where pausing the service will cause catastrophic results. Be
aware, though, that if you do this, Windows will report an error if it cannot
pause the service within three seconds. This same discussion applies to
stopping a service or to continuing a paused service. </p>
<p class=BodyText> </p>
<p class=BodyText> There
isn't much more to say on the subject of using separate threads for your
services. Actually, that statement is a bit misleading. The reality is that
there is so much more to say on this subject that it would take dozens of pages
to adequately cover it. I realize that this short example doesn't give you much
information on the nitty-gritty details of dealing with threads in services.
The reason is simply that services are so varied that I really can't anticipate
what issues you might encounter with a particular service you might write. </p>
<p class=BodyText> </p>
<p class=Subheads>Writing
Interactive Services</p>
<p class=BodyText> An
interactive service is one that can interact with the Windows desktop.
Generally, this means that the service can display a dialog box to the user.
Often the dialog box allows the user to configure some aspect of how the
service operates. The example program for the remainder of the subjects
discussed in this series is called PingService. The complete project is
available for download; see end of article for details. The service has the
following functionality and features: </p>
<ul>
<li>Pings
a remote machine at periodic intervals.
<li>If
the remote machine doesn't respond to the ping, the service takes one of two
actions depending on the service's configuration:
<li>Logs
the failure to the system Event Log.
<li>Sends
e-mail to a specified address notifying you of the failure.
<li>When
the remote machine comes back up, the event is logged (or e-mail sent).
<li>A
configuration dialog box allows you to set the remote machine name, the ping
interval, the notification type, the e-mail address, and the e-mail host to use
for e-mail notification.
<li>Configuration
data is stored in the registry to be reloaded the next time the service starts.
<li>Displays
an icon representing the service in the system tray.
<li>Displays
a pop-up menu for the tray icon.
</ul>
<p class=BodyText> </p>
<p class=BodyText> The
service has three units: The first is the service's main unit, the second is
the thread that performs the ping, and the third is the service's configuration
form. Figures 8 through 13 show each of the units and their headers. </p>
<p class=BodyText> </p>
<p class=Code><span class=Code><span Class=CodeGrn>#ifndef
PingServiceUH</span></span></p>
<p class=Code><span class=Code><span Class=CodeGrn>#define
PingServiceUH</span></span></p>
<p class=Code><span class=Code> </span></p>
<p class=Code><span class=Code><span Class=CodeGrn>#include
<SysUtils.hpp> </span></span></p>
<p class=Code><span class=Code><span Class=CodeGrn>#include
<Classes.hpp> </span></span></p>
<p class=Code><span class=Code><span Class=CodeGrn>#include
<SvcMgr.hpp> </span></span></p>
<p class=Code><span class=Code><span Class=CodeGrn>#include
<Controls.hpp> </span></span></p>
<p class=Code><span class=Code><span Class=CodeGrn>#include
<Menus.hpp> </span></span></p>
<p class=Code><span class=Code><span Class=CodeGrn>#include
<ExtCtrls.hpp> </span></span></p>
<p class=Code><span class=Code><span Class=CodeGrn>#include
"PingThreadU.h" </span></span></p>
<p class=Code><span class=Code> </span></p>
<p class=Code><span class=Code><b>class</b>
TBCB4UnlPing : <b>public</b> TService</span></p>
<p class=Code><span class=Code>{</span></p>
<p class=Code><span class=Code><b>__published</b>: <i> <span Class=CodeBlue>// IDE-managed Components</span></i></span></p>
<p class=Code><span class=Code> <b> void</b>
<b>__fastcall</b> BCB4UnlPingStart(TService
*Sender, <b>bool</b> &Started); </span></p>
<p class=Code><span class=Code> <b> void</b>
<b>__fastcall</b> BCB4UnlPingStop(TService
*Sender, <b>bool</b> &Stopped); </span></p>
<p class=Code><span class=Code> <b> void</b>
<b>__fastcall</b>
BCB4UnlPingExecute(TService *Sender); </span></p>
<p class=Code><span class=Code><b>private</b>: <i> <span Class=CodeBlue>// User declarations</span></i></span></p>
<p class=Code><span class=Code><b>public</b>: <i> <span Class=CodeBlue>// User declarations</span></i></span></p>
<p class=Code><span class=Code> TPingThread* PingThread; </span></p>
<p class=Code><span class=Code> <b> __fastcall</b>
TBCB4UnlPing(TComponent* Owner); </span></p>
<p class=Code><span class=Code> PServiceController <b>__fastcall</b> GetServiceController(<b>void</b>);</span></p>
<p class=Code><span class=Code><b>protected</b>:</span></p>
<p class=Code><span class=Code> <b> friend</b>
<b>void</b> <b>__stdcall</b> ServiceController(<b>unsigned</b>
CtrlCode); </span></p>
<p class=Code><span class=Code>};</span></p>
<p class=Code><span class=Code> </span></p>
<p class=Code><span class=Code><b>extern</b>
PACKAGE TBCB4UnlPing *BCB4UnlPing; </span></p>
<p class=Code><span class=Code> </span></p>
<p class=Code><span class=Code><span Class=CodeGrn>#endif</span></span></p>
<p class=Captions><b>Figure
8:</b> The header for
the PingService unit. </p>
<p class=BodyText> </p>
<p class=Code><span class=Code><span Class=CodeGrn>#include
"PingServiceU.h" </span></span></p>
<p class=Code><span class=Code><span Class=CodeGrn>#include
"ConfigU.h" </span></span></p>
<p class=Code><span class=Code><span Class=CodeGrn>#include
"PingThreadU.h" </span></span></p>
<p class=Code><span class=Code> </span></p>
<p class=Code><span class=Code><span Class=CodeGrn>#pragma
package(smart_init) </span></span></p>
<p class=Code><span class=Code><span Class=CodeGrn>#pragma
resource "*.dfm" </span></span></p>
<p class=Code><span class=Code> </span></p>
<p class=Code><span class=Code>TBCB4UnlPing
*BCB4UnlPing; </span></p>
<p class=Code><span class=Code> </span></p>
<p class=Code><span class=Code><b>__fastcall</b>
TBCB4UnlPing::TBCB4UnlPing(TComponent* Owner) </span></p>
<p class=Code><span class=Code> : TService(Owner) </span></p>
<p class=Code><span class=Code>{</span></p>
<p class=Code><span class=Code>}</span></p>
<p class=Code><span class=Code> </span></p>
<p class=Code><span class=Code>PServiceController
<b>__fastcall</b> TBCB4UnlPing::GetServiceController(<b
style='mso-bidi-font-weight:normal'>void</b>)</span></p>
<p class=Code><span class=Code>{</span></p>
<p class=Code><span class=Code> <b> return</b>
(PServiceController) ServiceController; </span></p>
<p class=Code><span class=Code>}</span></p>
<p class=Code><span class=Code><b>void</b> <b
style='mso-bidi-font-weight:normal'>__stdcall</b> ServiceController(<b
style='mso-bidi-font-weight:normal'>unsigned</b> CtrlCode) </span></p>
<p class=Code><span class=Code>{</span></p>
<p class=Code><span class=Code> BCB4UnlPing->Controller(CtrlCode); </span></p>
<p class=Code><span class=Code>}</span></p>
<p class=Code><span class=Code> </span></p>
<p class=Code><span class=Code><b>void</b> <b
style='mso-bidi-font-weight:normal'>__fastcall</b>
TBCB4UnlPing::BCB4UnlPingStart(TService *Sender, </span></p>
<p class=Code><span class=Code> <b> bool</b>
&Started) </span></p>
<p class=Code><span class=Code>{</span></p>
<p class=Code><span class=Code> PingThread = <b>new</b> TPingThread(<b>false</b>);</span></p>
<p class=Code><span class=Code> ConfigForm->LoadConfiguration();</span></p>
<p class=Code><span class=Code> Started = <b>true</b>;</span></p>
<p class=Code><span class=Code>}</span></p>
<p class=Code><span class=Code> </span></p>
<p class=Code><span class=Code><b>void</b> <b
style='mso-bidi-font-weight:normal'>__fastcall</b>
TBCB4UnlPing::BCB4UnlPingStop(TService *Sender, </span></p>
<p class=Code><span class=Code> <b> bool</b>
&Stopped) </span></p>
<p class=Code><span class=Code>{</span></p>
<p class=Code><span class=Code> PingThread->Terminate();</span></p>
<p class=Code><span class=Code> Stopped = <b>true</b>;</span></p>
<p class=Code><span class=Code>}</span></p>
<p class=Code><span class=Code> </span></p>
<p class=Code><span class=Code><b>void</b> <b
style='mso-bidi-font-weight:normal'>__fastcall</b>
TBCB4UnlPing::BCB4UnlPingExecute(TService *Sender) </span></p>
<p class=Code><span class=Code>{</span></p>
<p class=Code><span class=Code> <b> while</b>
(!Terminated) </span></p>
<p class=Code><span class=Code> ServiceThread->ProcessRequests(<b
style='mso-bidi-font-weight:normal'>false</b>);</span></p>
<p class=Code><span class=Code>}</span></p>
<p class=Captions><b>Figure
9:</b> The source code
for the PingService unit. </p>
<p class=BodyText> </p>
<p class=Code><span class=Code><span Class=CodeGrn>#ifndef
PingThreadUH</span></span></p>
<p class=Code><span class=Code><span Class=CodeGrn>#define
PingThreadUH</span></span></p>
<p class=Code><span class=Code><span Class=CodeGrn>#include
<NMsmtp.hpp> </span></span></p>
<p class=Code><span class=Code><span Class=CodeGrn>#include
<Psock.hpp> </span></span></p>
<p class=Code><span class=Code> </span></p>
<p class=Code><span class=Code><b>class</b>
TPingThread : <b>public</b> TThread {</span></p>
<p class=Code><span class=Code> <b> private</b>:</span></p>
<p class=Code><span class=Code> <b> bool</b>
ServerDownReported; </span></p>
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