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Seem to have encountered an issue that I can't really resolve. I have a client trying to write to a stream on port 4530.

This is a system running constantly, and when I got back to work monday morning, the system had caused Internet Explorer to stop working sometime during the weekend (Well, I'm not sure of this statement, but that's my theory - for now). Checking the logs, I found the following error, repeatedly:

System.IO.IOException: Unable to write data to the transport connection: An existing connection was forcibly closed by the remote host. ---> System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host
   at System.Net.Sockets.Socket.Send(Byte[] buffer, Int32 offset, Int32 size, SocketFlags socketFlags)
   at System.Net.Sockets.NetworkStream.Write(Byte[] buffer, Int32 offset, Int32 size)
   --- End of inner exception stack trace ---
   at System.Net.Sockets.NetworkStream.Write(Byte[] buffer, Int32 offset, Int32 size)
   at System.IO.StreamWriter.Flush(Boolean flushStream, Boolean flushEncoder)
   at System.IO.StreamWriter.Write(String value)

After some investigation, I found that MS Security Essentials had been updated during the weekend, even though these automatic updates should be turned off. Am I missing some setting to disable this? Is this at all the right theory, or could this essentially be caused by anything?

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migrated from Mar 24 '13 at 10:20

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Why did you use the 'silverlight' tag? there is no mention of it in your question! Is your client-that-sends-the-stream written in SL or the service-that-processes-the-stream? – quetzalcoatl Mar 18 '13 at 15:05
Thanks. Forgot to mention that there was a silverlight application running on top. – niwi Mar 19 '13 at 7:39

Would the exception remarks say it was closed by the remote host if it was due to the firewall? Do you have access to log files on the remote host?

MSE uses Windows Firewall for any blocking (it doesn't actually block ports itself) so I would check the firewall rules and log (on my system, the log is at %systemroot%\system32\LogFiles\Firewall\pfirewall.log; I believe on older systems (XP, Vista) the default path was just %systemroot\pfirewall.log).

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It's all on the same machine, so yes, I've got access to all logs. The stacktrace above is all I got out of it :S Firewall should be disabled on the system. I've also disabled updates, and even disabled the update service. Going to let the system run overnight to see if it's any better. If not, I really don't know what to do :S – niwi Mar 18 '13 at 14:35
I resolved this. See my own answer below. Thanks for your help and suggestions. – niwi Mar 19 '13 at 7:43
up vote 0 down vote accepted

I found the answer to this. Even though I'd disabled the automatic windows updates, it seems (according to event logs on system) that MS Security Essentials had done two updates throughout the weekend, as previously mentioned.

I found that I actually had to disable the update service it self in order for this to be completely shut down.

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So, I was wrong. Your question is offtopic and the title was perfectly valid :) Reverted the title. You'd probably get more help on the sysadmin or networking branch of stackexchange. If you have resolved your problem, please mark one of the answers (either Ryan's or your own) as 'accepted' - that large green tick below the up/down score arrows. – quetzalcoatl Mar 19 '13 at 8:56

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