CODEWITHSUNDEEP
multithreadingdelphiwindows-servicesipcado
iMan Biglari
iMan Biglari

Reputation: 4776

Cromis IPC Synchronization - Application stops responding

I have a service application which connects to MSSQL using TADOConnection and provides client applications with some data using Cromis.IPC's TIPCServer object. This service application might be installed on the same machine which is running MSSQL, and might start before MSSQL service. So, I can not connect to ADO in OnServiceStart event. I tried to connect to ADO in OnExecuteRequest event of TIPCServer, but since it is running in a separate thread, I got "CoInitialize has not been called". Then, I tried to synchronize this with my main thread like this:

TThread.Synchronize(nil, ConnectDB);

but it didn't work. My application stops responding right there.

Next, I modified the OnExecuteRequest event to pass the thread which is calling it as a parameter, and I tried this:

AThread.Synchronize(AThread, ConnectDB);

But no change. When I turned on Use debug DCUs, I found out that my application stops responding on this line:

function WaitForSyncWaitObj(P: Pointer; Timeout: Cardinal): Integer;
begin
  Result := WaitForSingleObject(THandle(P), Timeout); // <-- I'm stuck here...
end;

I'm completely lost. Any ideas?

PS: I didn't provide my code to prevent cluttering the question. If you need any part of it, just let me know.

PS 2: Before this, I tried to use a Timer in my service application to wait for a period before connecting to MSSQL. It seems like MSSQL starts pretty soon, even before network drivers are loaded (I have McAfee VSE 8.7 installed which replaces the network driver). My service connects to MSSQL, but then, when the network driver is loaded, the connection is broken. If there is a way to tell windows (XP and later) to start a service after network driver is loaded, my problem is solved. Any hint is really appreciated.

Upvotes: 1

Views: 355

Answers (1)

Ken White
Ken White

Reputation: 125729

Call CoInitialize(nil); in your TThread constructor, and CoUnitialize in it's destructor. Both of them are declared in the ComObj unit; you may need to add it to your uses clause in the unit containing the thread class.

Database connections are thread-specific (meaning each thread has to have it's own connection), and ADO requires COM; that means that the thread has to initialize COM for itself, and should release it when the thread ends.

Upvotes: 1

Related Questions