Re: [Ncat] I'd like to contribute a feature

[David Fifield <david () bamsoftware com>]

On Thu, Sep 02, 2010 at 03:43:44PM +0200, miniBill wrote:
> 2010/7/29 David Fifield <david () bamsoftware com>:
> > Thanks for your interest! Please help us understand what you have in
> > mind by showing some example command lines and explaining how they will
> > work. A use case, a real-world problem that this will solve, is good
> > too.
> >
> > You will want to refer to this documentation for getting the source
> > code.
> >
> > http://nmap.org/book/install.html#inst-svn
> > http://nmap.org/book/inst-source.html
> >
> > As for code organization, --sh-exec and --exec are handled in the files
> > ncat_posix.c and ncat_exec_win.c. Whatever changes you make should work
> > on both POSIX and Windows. With luck, you'll only have to use the netrun
> > and netexec function, which are already abstracted.
>
> I've rapidly checked ncat_listen.c which is the file which, as far as
> I could understand,
> actually invokes the platform-specific calls. As it works now it
> executes the command
> every time someone connects. What I would like to do is to have one
> single command
> execution, which collects all the users' input, and whose output is
> copied to every user.
> As small as I can understand it, it won't be easy.

I don't think it will be that hard. You can see that in ncat_listen.c,
there is special code that handles stdin and stdout; stdin and stdout
are treated like a special kind of "client." You would start a
subprocess with netrun and then treat its file handles specially also. I
think, in essence, that you want to replace the Ncat server's stdin and
stdout with that of another process. You are right that --exec doesn't
work that way.

You might be able to implement this with a Perl script that runs your
subcommand, runs ncat --listen, and connects their filehandles with dup
or dup2.

You might try starting a server in --broker mode, and then connect to it
with a client using --exec. Then that client will receive anything sent
by any other connecting client, and it will send its output to all other
connected clients.

David Fifield
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