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Re: Closing socket when input file ends?
From: David Fifield <david () bamsoftware com>
Date: Tue, 1 May 2012 12:44:06 -0700

On Tue, May 01, 2012 at 11:12:11AM -0800, Britton Kerin wrote:
Hi guys,

First: loving nmap/ncat a lot.  Thanks all.

I'm using ncat with an embedded device like so:

   nmap 192.168.1.42 50000 <query.bin >response.bin

The thing is it never seems to close the connection.  I can use --idle-timeout
to kill it but I sort of wonder why it doesn't automatically close the socket
when input EOF stdin like cat does?

This is by design. We can't close the socket when local input ends
because the remote host may still be sending. There's a litte bit about
it here:
http://nmap.org/ncat/guide/ncat-other-options.html
The only exception is with --send-only, where we know we will ignore
anything from the remote host, so it's always safe to close the socket.

There's an earlier discussion on this topic here:
http://seclists.org/nmap-dev/2009/q2/151
A use case where you don't want the socket closed is here:
http://seclists.org/nmap-dev/2009/q2/154

Also, when typing in put manually I would expect CNTRL-D to send EOF,
but I'm not sure if it does or not, or does but it doesn't close
connection, or what.

It sends EOF. Run with the -vvv option to see the Nsock event:
NSOCK (0.4860s) Callback: READ EOF for EID 26 (peer unspecified)

David Fifield
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