Re: Socket inheritance with fork/dup2/exec

["Jim Powers" <jim dot powers at powers-consulting dot com>]

Corinna,

I took your suggestion and downloaded the latest sanpshot (cygwin1-
20070616.dll) and that fixed the problem.  The Win32 version of the client 
compiled with VC8 now works fine.

Thanks!!

Jim

Corinna Vinschen <corinna-cygwin@cygwin.com> said:

> On Jun 21 22:45, Jim Powers wrote:
> > Hi,
> > 
> > I am redirecting the stdout of a child process to a socket via the 
standard 
> > fork/dup2/exec paradigm and then reading and displaying the output.
> > 
> > This works fine if the exec'd child process is compiled using gcc under 
> > cygwin. However, it fails with an "Invalid file handle" error when 
compiled 
> > using VC8 under windows.
> > 
> > I've included both the parent and child code below.
> > 
> > I am running cygwin 1.5.24 and gcc3.4.4.
> 
> This is almost certainly a drawback of the method used for duplicating
> sockets to child processes used in Cygwin 1.5.24 and before
> (WSADuplicateSocket/WSASocket).  This only works reliable if the child
> knows that the descriptor is a socket.  Usually server applications
> using sockets don't duplicate the socket to the child processes, but
> instead use pipes or pseudo terminals on the local connection, so that's
> not a standard problem.
> 
> However, the next version of Cygwin will use standard DuplicateHandle
> calls as for normal file handles.  Consequentially your
> your test application appears to work with a Cygwin built from CVS:
> 
>   $ ./sock-cyg-win-parent ./sock-cyg-win-child.exe
>   hellohellohellohellohello^C
> 
> You could try a developer snapshot from http://cygwin.com/snapshots/
> 
> As a workaround for Cygwin 1.5.x, use pipes, as already noted, or pseudo
> terminals.
> 
> 
> Corinna
> 
> -- 
> Corinna Vinschen                  Please, send mails regarding Cygwin to
> Cygwin Project Co-Leader          cygwin AT cygwin DOT com
> Red Hat
> 
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-- 
Jim Powers
Powers Consulting Services, Inc.
jim.powers@powers-consulting.com
937-271-5523



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