We have been having a lot of trouble with connection failures in some of our database apps. I've turned on trace flags 4029 and 3689 on our SQL box, this was recommended to help try and track down the problem. After setting these on we've been seeing entries like these below in the SQL error log and application event logs.
2008-10-17 16:22:09.30 spid261 Error: 17824, Severity: 20, State: 1
2008-10-17 16:22:09.30 spid261 Could not write to Net-Library 'SSNETLIB', loginname '', hostname 'A Client'. Connection closed..
2008-10-17 16:22:09.30 spid261 Error: 17059, Severity: 18, State: 0
2008-10-17 16:22:09.30 spid261 Operating system error 10054: An existing connection was forcibly closed by the remote host...
2008-10-16 14:33:01.53 spid276 Error: 17824, Severity: 20, State: 1
2008-10-16 14:33:01.53 spid276 Could not write to Net-Library 'SSNETLIB', loginname '', hostname 'The SQl box'. Connection closed..
2008-10-16 14:33:01.53 spid276 Error: 17059, Severity: 18, State: 0
2008-10-16 14:33:01.53 spid276 Operating system error 4: The system cannot open the file...
We also have Wireshark capturing the traffic on port 1433 but this isn't really telling us anything useful.
I should point out here that the SQL box is virtual but is dedicated. It is SP4 and also fully patched barr the very latest MS updates.
Does anyone have any ideas what could be wrong here. This is a huge problem for us and we are beginning to lose favour with our users the longer this goes on.
I appreciate any help you can give here, and if you need any more info I'll tell you what I can.