Re: Socket's close() doesn't close connection (old bug?)

[David Daney <ddaney at avtrex dot com>]

Martin Egholm Nielsen wrote:
> Hi Daney,
>
> > > > In my eager to reproduce another bug I've stumbled across yet 
> > > > another strange issue - namely that Socket's close() doesn't close 
> > > > underlying socket (with no traffic), nor "wake up" a blocked 
> > > > read-thread (as a consequence)...
> > >
> > >
> > >
> > > Blah blah blah, this turned out to be reported already:
> > >
> > > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15430
> > >
> > > Unfortunately still open ;-)
>
>
> > Check the above PR for my little C program the demonstrates how by 
> > adding a call to shutdown() before the close() that the blocked read() 
> > returns.  I think with a small amount of hacking we can use this 
> > technique to terminate the blocked thread with the proper exception 
> > being thrown.
>
> Really?! Reading here:
>
> http://www.ecst.csuchico.edu/~beej/guide/net_old/#closedown
>
> shutdown(s, SHUT_RDWR);
>
> and
>
> close(s);
>
> are identical...

They are not identical.  shutdown() closes the socket. close() 
disconnects a process from the socket allowing the OS to close it when 
there are no more references to it.  If a thread is blocked reading from 
the socket there will be a reference to it as long as it is blocked.

David Daney.