[fpc-pascal] RE: Interprocess Communication

Jason P Sage jasonpsage at jegas.org
Thu Mar 1 08:02:05 CET 2007

I've made some progress with the simpleipc unit however I found a disturbing
"quirk" for the Windows implementation.

I can definitely make an IPC Server and an IPC client that can send messages
to that server...


If the IPC client is invoked as a cgi application via a web server, it never
can send a message to the IPC server. This is repeatable.

I looked at the windows simpleipc.inc (Win32 version) and there is code for
window handles and such.

Is it possible this implementation of simpleipc only works when gui
resources are available?

I thought I had this thing nailed - but it looks like the simpleipc unit
just doesn't work when fired from apache. 

This is confirmed by the fact that I can execute the program from a command
line and the message does in fact get passed (I see the message appear in
the console window that the server is running).

When I execute the program via cgi - I get an error message in the web page
that is generated by my cgi app - so I know its firing. Furthermore the
error message specifically tells me where the failure is. It fails when I
try to make the semaphore "active". See Snippet below.

---Code Snippet----BEGIN

  With TSimpleIPCClient.Create(Nil) do 
    if not bServerOffline then

---Code Snippet----END

This code falls into the except block when executed via web software like
apache, but from the command line falls through without error.

Does anyone have any suggestions? Does the Windows version of simpleipc not
work if the application can not get a window handle? 

Am I doing something wrong? Wouldn't be the first time. 

Any and all help is appreciated.

Best Regards,
Jason P Sage

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