I am having an issue with pinging that I would like some help/advise if anyone can.

I have a situation where users log on via a laptop, do some work then close the laptop down without terminating the app.  When they open the laptop back up the app is still active and pinging away, but the session on the server has been removed by this time.

I an ApplicationEvents setup with an app wide exception handler, but for the life of me I cannot get this event to fire on the ping event.  I can get it to work however if I try and request some other info from the database.

What I want to do terminate the application if the ping keeps failing after so many tries.

Does anyone know why the ping event is not firing?  Do I need to write something myself to manage the ping failure?

I am using DBISam4.42

Regards
David.

David


I'm guessing that when you say "close the laptop down" you mean close the lid and send it to sleep or hibernate. If so, whilst I've never tried it, I assume that the app stops doing anything until the lid is reopened and then it starts up where it left off. By that time the server has gotten bored and dumped the session.

I never used c/s in DBISAM so I'm not sure what events you have to play with, and since if my guess is right then machine won't have been in a state to receive anything back from the server its awkward. Since the ping is just to keep the server from thinking you've run away I don't know if Tim even bothers with the response, if he does and its surfaced I can't find it.

On the good news side, whilst I don't know anything to handle the pinging I do know about handling the screen powering off / on since I had a problem with it.

You can trap for when the screen goes on / off and stop pinging / reconnect as appropriate

I hope what I've posted below is of use and understandable.




{POWER BROADCAST STUFF}
const
WM_POWERBROADCAST = 536;
PBT_POWERSETTINGCHANGE = $8013;
DEVICE_NOTIFY_WINDOW_HANDLE = 0;
GUID_MONITOR_POWER_ON: TGUID = '{02731015-4510-4526-99E6-E5A17EBD1AEA}';

type
HPOWERNOTIFY = Pointer;
PHPOWERNOTIFY = ^HPOWERNOTIFY;

PPowerBroadcastSetting = ^TPowerBroadcastSetting;
TPowerBroadcastSetting = record
 PowerSetting: TGUID;
 DataLength: DWORD;
 Data: array[0..0] of UCHAR;
end;

function RegisterPowerSettingNotification(const hRecipient: THandle; const PowerSettingGuid: TGUID; const Flags: DWORD): HPOWERNOTIFY; stdcall;
external user32 name 'RegisterPowerSettingNotification';
function UnregisterPowerSettingNotification(Handle: HPOWERNOTIFY): BOOL; stdcall;
external user32 name 'UnregisterPowerSettingNotification';



procedure TMainForm.WMPowerBroadcast(var msg: TMessage);
var
Setting: TPowerBroadcastSetting;
begin
if msg.WParam = PBT_POWERSETTINGCHANGE then begin
 Setting := PPowerBroadcastSetting(msg.LParam)^;
 if IsEqualGUID(Setting.PowerSetting, GUID_MONITOR_POWER_ON) then begin
  MonitorIsOn := DWORD(Setting.Data[0]) = 1;
  MonitorOnChange := Now;
  if MonitorIsOn then begin
   CheckingAlarms.Active := CheckingAlarms.Tag = 1;
   BackgroundSearch.Active := BackgroundSearch.Tag > 0;
   Blinker.Enabled := Blinker.Tag = 1;
  end else begin
   CheckingAlarms.Active := False;
   BackgroundSearch.Active := False;
   Blinker.Enabled := False;
  end;
 end;
end;
inherited;
end;


in form create
MonitorOnCheck := RegisterPowerSettingNotification(Handle, GUID_MONITOR_POWER_ON, DEVICE_NOTIFY_WINDOW_HANDLE);
MonitorIsOn := True;
MonitorOnChange := Now;


in form close
  UnregisterPowerSettingNotification(MonitorOnCheck);


in private for form type definition
 procedure WMPowerBroadcast(var msg: TMessage); message WM_POWERBROADCAST;

Roy Lambert

Hi Roy.

Thanks for the fast response.  I think your code sample could certainly come in very useful.  

Many thanks for posting it.  I will play around with this.

Regards
David.

Roy Lambert wrote:

David


On the good news side, whilst I don't know anything to handle the pinging I do know about handling the screen powering off / on since I had a problem with it.

You can trap for when the screen goes on / off and stop pinging / reconnect as appropriate

I hope what I've posted below is of use and understandable.

David,

<< I am having an issue with pinging that I would like some help/advise if anyone can.

I have a situation where users log on via a laptop, do some work then close the laptop down without terminating the app.  When they open the laptop back up the app is still active and pinging away, but the session on the server has been removed by this time. >>

This is the hibernation powering down the network adapter, and there's really nothing you can do about it, apart from telling Windows that you don't want the machine to hibernate while your application is still running.  This may or may not be do-able, depending upon your users and how they use the application.

I'd link to some more information on this from Stack Overflow, but it's down at the moment.

Tim Young
Elevate Software
www.elevatesoft.com