Smartly dealing with CLOSE-WAIT states

sdyates has asked for the wisdom of the Perl Monks concerning the following question:

Well folks, this one has been puzzling me for weeks. I have read RFCs and many documents, but it appears that no one can give me a definate.

Background

Trying to determine the level of close-wait states on an Internet0based application. Netstat -na is very good for getting the basic info. Now I can monitor the states with a script. However, while I cannot terminate the sockets, I can restart the application, causing all sockets to resolve themselves. However, before I start monkeyong around with this, I need to get definitive answers as the the cause of close-wait states and instead of writing a script to restart an application after a number of close-wait state appear, perhaps a script to prevent them would be better?

Below is a simple diagram taken from the RFC on TCP based connections:

TCP A TCP B
1. ESTABLISHED ESTABLISHED
2. (Close) FIN-WAIT-1 --> <SEQ=100><ACK=300><CTL=FIN,ACK> --> CLOSE-WAIT
3. FIN-WAIT-2 <-- <SEQ=300><ACK=101><CTL=ACK> <-- CLOSE-WAIT
4. (Close) TIME-WAIT <-- <SEQ=300><ACK=101><CTL=FIN,ACK> <-- LAST-ACK
5. TIME-WAIT --> <SEQ=101><ACK=301><CTL=ACK> --> CLOSED
6. (2 MSL) CLOSED

Can anyone provide me with a few guidlines on which way to go? Or, has something already been created to do the job.

By the way, I also tried tunning the tcp values of the OS which has made little to no difference.

Comment on Smartly dealing with CLOSE-WAIT states

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Re: Smartly dealing with CLOSE-WAIT states by fglock (Vicar) on Sep 27, 2002 at 17:15 UTC
The "clean" way to go is to make your applications close (or shutdown) their sockets after receiving end-of-file.	[reply]
Re: Smartly dealing with CLOSE-WAIT states by fglock (Vicar) on Sep 28, 2002 at 06:10 UTC
Looks like there are no news since 155873. You really have to restart the application to have the sockets closed. Applications should behave better.	[reply]
Re: Re: Smartly dealing with CLOSE-WAIT states by sdyates (Scribe) on Oct 01, 2002 at 21:11 UTC
Looks like, yes is quite similar. I have tried to rig a script that will force a closure of these sockets, but the more i read and try to do the impossible, the more I realise it is the responsability of the applicaiton. Unfortunately, it is a java application, so the water becomes muddier. Thanks for everyone's help. I just needed some other voices to see if there was not someone who had created a great perl module to deal with these messes :)	[reply]