Spurious LISTENING ports open during network connections (was Re:Weird Naim.exe network usage?)

[Daniel Reed <n at ml dot org>]

On 2003-10-24T15:22-0500, darkacorn@verizon.net wrote:
) that for some reason naim.exe was listening on tcp sockets, and not only
) that but it changes quite frequently while naim.exe is running. So let me
) just state this again, it is listening on TCP sockets. They are also real
) because I have confirmed by telneting to them. Nothing is printed or
) anything, it just sits there. Has anyone experienced naim.exe listening on
) TCP sockets? I have no modules loaded I confirmed with /modlist.

I was out of town when you first asked about this, and was initially unable
to reproduce it. However, it does appear that your assessment was correct,
but it does not appear that this is naim-specific.

When I start up naim, netstat -a -n -o | grep winpid does not show anything
(either listening or established). When I /connect, the same netstat now
shows a connection ESTABLISHED with AOL's servers, and two LISTENING sockets
on seemingly random ports (one binded to 127.0.0.1, the other allowing
connections from anywhere).

However, Cygwin's telnet utility appears to behave identically on my system.
If I start telnet and run netstat -a -n -o | grep winpid, it does not show
anything. If I enter "open n.ml.org 80" then immediately I see something
like:
  TCP    0.0.0.0:4705           0.0.0.0:0              LISTENING       2780
  TCP    127.0.0.1:4718         0.0.0.0:0              LISTENING       2780
  TCP    192.168.1.101:4705     24.161.40.144:80       ESTABLISHED     2780

These LISTENING sockets stay open for the duration of the connection, but
the 127.0.0.1 port changes after every packet I send out (i.e. it will
change from 4718 to a higher number after every command I type).

I am not familiar enough with how the networking code operates, so I am not
sure what the impact of this might be. It looks like this may be a known
issue, referenced at http://cygwin.com/ml/cygwin/2000-06/msg00947.html, so I
do not believe it is a major problem. However, I will defer if another
Cygwin maintainer has any words of wisdom.

-- 
Daniel Reed <n@ml.org>	http://naim-users.org/nmlorg/	http://naim.n.ml.org/
"Murphy's Law is recursive. Washing your car to make it rain doesn't
work."

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