I have an ASP.NET application running on a client server (W2k3, IIS6, .NET 2.0). FWIW, this is a Test instance, it hasn't been moved into Production yet. So it is not running under SSL, load balancing, etc.

When I access one of the pages on their server from our office, the page gets hit once. Inspecting the IIS logs (c:WINDOWS\system32\LogFiles\W3SVC1) show a GET for that page, then I push a button on the page and the log file shows a POST. This seems to be working fine so far.

Now when I remote into the client's network and access the page from one of their local machines, the log file shows a GET, then I push the button on the page and the log shows two POSTs at the same second. The first one shows status (sc-status, sc-substatus, sc-win32-status) 200 0 64, the second shows 200 0 0.

In the log file, both POSTs are identical. Basically the log looks like this (except I masked some of the data):

#Fields: date time s-ip cs-method cs-uri-stem cs-uri-query s-port cs-username c-ip cs(User-Agent) sc-status sc-substatus sc-win32-status 
2009-08-11 20:19:32 x.x.x.x GET /File.aspx - 80 - y.y.y.y Mozilla/4.0+(compatible;+MSIE+8.0;+Windows+NT+6.0;+WOW64;+Trident/4.0;+SLCC1;+.NET+CLR+2.0.50727;+.NET+CLR+3.5.21022;+.NET+CLR+3.5.30729;+.NET+CLR+3.0.30618;+MDDR;+OfficeLiveConnector.1.4;+OfficeLivePatch.0.0) 200 0 0
2009-08-11 20:19:45 x.x.x.x POST /File.aspx - 80 - y.y.y.y Mozilla/4.0+(compatible;+MSIE+8.0;+Windows+NT+6.0;+WOW64;+Trident/4.0;+SLCC1;+.NET+CLR+2.0.50727;+.NET+CLR+3.5.21022;+.NET+CLR+3.5.30729;+.NET+CLR+3.0.30618;+MDDR;+OfficeLiveConnector.1.4;+OfficeLivePatch.0.0) 200 0 64
2009-08-11 20:19:45 x.x.x.x POST /File.aspx - 80 - y.y.y.y Mozilla/4.0+(compatible;+MSIE+8.0;+Windows+NT+6.0;+WOW64;+Trident/4.0;+SLCC1;+.NET+CLR+2.0.50727;+.NET+CLR+3.5.21022;+.NET+CLR+3.5.30729;+.NET+CLR+3.0.30618;+MDDR;+OfficeLiveConnector.1.4;+OfficeLivePatch.0.0) 200 0 0

The problem is, the page is getting hit twice. The database performs an operation for the first request, then the second request detects that a duplicate operation is being performed and throws an error message. The users think their operation failed, but it actually succeeded.

The error description of sc-win32-status 64 is: "The specified network name is no longer available." This leads me to believe, given that both POST requests show an HTTP status of 200, that the server is successful in serving the request, but the client is never notified and resubmits the request.

• How can I troubleshoot this?

• Any ideas what could be causing this behavior on their internal network only?

• I should mention, this is happening at two separate client sites, but does not happen at six of our other client sites, or in our office, or connecting to any of our eight clients over the web.

• What could be making this reproducible 100% of the time on their local network but 0% of the time anywhere else?

Update: I found a very small number of the duplicated POST requests had sc-win32-status of 995 instead of 64 as originally reported. The error description of sc-win32-status=995 is: "The I/O operation has been aborted because of either a thread exit or an application request." This doesn't make any sense (considering I have full access to the code). I still don't understand how or why this issue is occurring, but the new error code leads me to believe it may not be a network issue after all and I am now investigating the possibility of a random code bug.