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From: Tony <truand.tony@gmail.com>
Newsgroups: comp.lang.ada
Subject: Re: Aborting a call to Accept_Socket
Date: Tue, 21 Apr 2009 09:32:07 -0700 (PDT)
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Date: 2009-04-21T09:32:07-07:00
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On 21 avr, 18:21, "Dmitry A. Kazakov" <mail...@dmitry-kazakov.de>
wrote:
> On Tue, 21 Apr 2009 08:40:13 -0700 (PDT), Tony wrote:
> > I would like to abort a call to Accept_Socket() if no connection
> > request arrives within a specified time (20 seconds). =A0For me, a quit=
e
> > simple solution (perhaps not safe) is to use an asynchronous transfer
> > of control like this:
> > --****************************************************
> > =A0 =A0procedure Server is
> > =A0 =A0 =A0 =A0...
> > =A0 =A0begin
> > =A0 =A0 =A0 =A0GNAT.Sockets.Initialize;
> > =A0 =A0 =A0 =A0...
> > =A0 =A0 =A0 =A0loop
> > =A0 =A0 =A0 =A0 =A0 =A0...
> > =A0 =A0 =A0 =A0 =A0 =A0select
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0delay 20.0;
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0exit;
> > =A0 =A0 =A0 =A0 =A0 =A0then abort
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0GNAT.Sockets.Accept_Socket (...);
> > =A0 =A0 =A0 =A0 =A0 =A0end select;
> > =A0 =A0 =A0 =A0 =A0 =A0...
> > =A0 =A0 =A0 =A0end loop ;
> > =A0 =A0end Server;
> > --****************************************************
> > The expecting behaviour was the end of the program after 20 seconds
> > (if no connection request arrives). I observe : after 20 seconds the
> > program will terminate only if =A0a connection request arrives.
> > Is this behaviour correct?
>
> Yes, it is. Asynchronous transfer of control is not guaranteed to work wi=
th
> an outstanding calls. Most likely it does not work as in this case. The
> behavior is correct because Ada does not know how to abort a socket
> operation in order to implement this statement. Ada RM contains a list of
> abort deferred things, which includes potentially any call to any externa=
l
> operation. Specifically for sockets there is a solution: you close the
> socket from another task. That will kill accept with an error code.
>
> --
> Regards,
> Dmitry A. Kazakovhttp://www.dmitry-kazakov.de

That's what I suspected, thanks a lot for your confirmation.
Regards.
Tony.