FIN_WAIT_2

[Charles Swiger]

On Mar 21, 2005, at 12:02 PM, Robert Gogolok wrote:
> The webserver is running FreeBSD, and currently I get many FIN_WAIT_2 
> states:
> # netstat -n -p tcp | grep FIN_WAIT_2 | wc -l
> 48
>
> I wonder WHAT is responsible for sending every 5 minutes ACK messages 
> to the clients in FIN_WAIT_2 state?  tcp.inet.tcp.always_keepalive 
> seems to be something else

The TCP stack wants the remote end to acknowledge the last FIN it sends 
and close the connection cleanly, and there is a timer (2 * MSL?) which 
gets started when a connection moves into the closing stages 
(FIN_WAIT_1, FIN_WAIT_2, LAST_ACK).

It's not uncommon for some clients (think dialup users running Win98), 
to drop the connection rather rather than close it properly.  Your 
system should time out these connections after a while.

-- 
-Chuck