Re: ncat 5.10BETA handling of -l -p is not compatible with nc-1.10

[Fyodor <fyodor () insecure org>]

On Fri, Jan 08, 2010 at 05:32:00PM +0100, Denys Vlasenko wrote:
> Hi,
>
> Every reimplementation of netcat seems to try to break
> this syntax:
>
> nc -l -p 123    # listen on local port 123
>
> GNU nc, openbsd's nc all have it broken. And ncat is no exception.
> "You too, Brutus". IIRC they even break it in different ways -
> they have different ways to specify local port: as a parameter
> to -l option, as a standalone port parameter etc... AARRGGHH...
>
> This makes users' lives harder for no apparent benefit.

One difference between ncat and those other reimplementations is that
we don't use the name "nc".  So you can have both installed at once,
and if you specifically request "ncat", then you know what syntax
you're going to get.  I think our syntax for listening on port 123
("ncat -l 123") is preferable to the longer "nc -l -p 123".  And as
David noted, we do give an error message which explains the problem if
you try to use -p with -l.

That being said, I also agree with David that it would be reasonable
for us to just "do what the user wants" in the -l -p case.  At least
as long as the code change is simple.  I think a warning message would
still be warranted, at least in verbose mode.

Cheers,
-F
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