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

[David Fifield <david () bamsoftware com>]

On Fri, Jan 08, 2010 at 01:33:19PM -0800, Fyodor wrote:
> 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.

I committed the code to make -p set the listen port. I also made it an
error if you try to give more than one port, like
        ncat -l 80 443
        ncat -l -p 80 443
I don't know what to print as a warning. "You don't need the -p with
Ncat"? It makes me think of Google's "Save time by hitting the return
key instead of clicking on the search button."

David Fifield
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