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lsmgms

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Socket stop responding

Hi,

I have a server application opens two sockets, 1 for TCP (listenning to any address)and 1 for UDP.  After few days with clients keep talking to that server, both of the socket dead.  The machine is multi host with 1 internal IP and one public IP.  The following tests have been carried out for diagonis:

- Netstat
Proto  Local Address          Foreign Address             State
TCP    0.0.0.0:port_num           0.0.0.0:0                        LISTENING
TCP   Internal_ip:port_num   Other_internal_ip     CLOSE_WAIT
UDP  0.0.0.0.port_num     *.*

Although it showed the TCP socket is still listenning but no connection can be establish to that port again.  I suspect CLOSE_WAIT have somehow locked the socket buffer.

- Network monitor
All the connection to the TCP port has been return with ACK+RST.

The only thing that I can guess is somehow the TCP stack was failed or OS (WINNT Serivce Pack 6) bug.  I know this question will not have answer and I will give the point to most informatic comment and if more than 1, I will request to distribute the point.  My current solution is to write a watchdog problem which occasionally opens a connection to the socket and reboots PC when failed after few retries.  However, tt will interrupt the service.  Thanks for any advice.
ASKER CERTIFIED SOLUTION
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Axter
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jhance

My guess here is that you have a leak of some sort that over time is exhausing some resource on the server.

Have you carefully examined your code to make sure that you are not leaving any handles or memory allocated as things progress?
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ASKER

Axter,

The linger is on all the while.  All the sockets closed by shutdown() first following by flusing buffer.  What are things that you suspect?
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ASKER

jhance,

Is should not have any resource leak because I always using performance monitor to check.  At least I am sure there are no handle and memory leak.  The program has been tested for quite a few days before in last few months.  This is the first time it occured.
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ASKER

One more thing that I should mention here is the application also has some SQL server database function, which may be also quiet busy and consumes a lot memory and processor time.  Is it relevant?
lsmgms,
If you're goal is to keep the sockets connected continuously, then using the SO_KEEPALIVE option will help keep the sockets connect even when there's an interupt.
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ASKER

Hi,

Actually I do not need keep sockets connected continuously because worse comes to worst, the user can just ask for new session.

I am confused about this:
- Since 0.0.0.0 is still listenning, it should be able to allow a new connection established.  The Reset flag almost tells us the socket is not available.
- CLOSE_WAIT means the FIN has been received from client, but somehow server socket cannot close socket.  What are the things that blocking it?
- Even the socket is hanging on CLOSE_WAIT, but it should not a problem becuase listenning socket is still alive.

Thanks
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ASKER

Some add on:

I have some in-bank keep alive message that will ensure the remote client is still alive.  Also, I think SO_KEEPALIVE cannot help this problem because the server has received FIN from client (CLOSE_WAIT) and diabled sending data including probe(howver, I am not so sure about this).  
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ASKER

I have posted 0 points to moderator for points award.

Greetings, I have processed the point split for you as requested here:
https://www.experts-exchange.com/questions/Q.20295329.html
Points for jhance -> https://www.experts-exchange.com/jsp/qShow.jsp?qid=20295366
:) Moondancer - EE Moderator