Re: [TUHS] sockets (was Re: First appearance of named pipes)

[Peter Pentchev <roam@ringlet.net>]

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On Sat, Mar 28, 2020 at 01:12:35PM +0200, Peter Pentchev wrote:
> On Thu, Mar 26, 2020 at 01:38:17PM +1100, Dave Horsfall wrote:
> > On Wed, 25 Mar 2020, Grant Taylor via TUHS wrote:
> > 
> > > · netcat's STDOUT to grep's STDIN
> > > · grep's STDOUT to netcat's STDIN
> > 
> > Are you trying to set up a loop of processes or something?  I'm not sure if
> > that is even possible, although you can't rule out creative uses of dup2()
> > etc...
> 
> This can't really be done with netcat, but it's quite easy to do with
> socat; here's an example with a trivial program that reads lines from
> its standard input and writes a single line to its standard output:
> 
>     [roam@straylight ~]$ socat -v tcp4:nimbus.fccf.net:25 exec:./heysmtp.py
>     > 2020/03/28 13:09:04.005497  length=48 from=0 to=47
>     220 nimbus.fccf.net ESMTP Postfix (Debian/GNU)\r
>     < 2020/03/28 13:09:04.018931  length=6 from=0 to=5
>     QUIT\r
>     > 2020/03/28 13:09:04.035387  length=15 from=48 to=62
>     221 2.0.0 Bye\r
>     [roam@straylight ~]$
> 
> All the output was actually from socat because of the "-v" option
> specified.

...but, of course, this is still not what Derek was talking about
earlier - there is no separation of the file descriptors connected to
the socket: closing the stdout one would not result in a FIN being sent
along the line.

G'luck,
Peter

-- 
Peter Pentchev  roam@{ringlet.net,debian.org,FreeBSD.org} pp@storpool.com
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