We have a windows application, it connects to a web service (XML web service hosted on a Windows 2008 Server IIS 7.5, no antivirus) and fetches some data to the client. But sometimes (around 5%-10% of the requests), it gives an error when trying to connect web service.

Here is the client application error log;

Exception:System.Net.WebException: The underlying connection was closed: The connection was closed unexpectedly.
at System.Web.Services.Protocols.WebClientAsyncResult.WaitForResponse()
at System.Web.Services.Protocols.WebClientProtocol.EndSend(IAsyncResult asyncResult, Object& internalAsyncState, Stream& responseStream)
at System.Web.Services.Protocols.SoapHttpClientProtocol.EndInvoke(IAsyncResult asyncResult)
at APPClient.APPFPService.WEBService.EndAddMoney(IAsyncResult asyncResult)
at APPClient.BLL.ServiceAgent.AddMoneyCallback(IAsyncResult ar)

From other hand, on the web server, i checked HTTP error logs and i see a long file like this;

2014-06-05 14:02:04 65.82.178.73 53798 SERVER.IP.ADDRESS 80 - - - - - Timer_ConnectionIdle -
2014-06-05 14:07:24 76.109.81.223 58985 SERVER.IP.ADDRESS 80 - - - - - Timer_ConnectionIdle -
2014-06-05 14:07:39 76.109.81.223 2803 SERVER.IP.ADDRESS 80 - - - - - Timer_ConnectionIdle -
2014-06-05 14:08:59 76.109.81.223 52656 SERVER.IP.ADDRESS 80 - - - - - Timer_ConnectionIdle -
2014-06-05 14:09:05 65.82.178.73 53904 SERVER.IP.ADDRESS 80 HTTP/1.1 POST /webservice/webservice.asmx - 2 Timer_EntityBody SYPService
2014-06-05 14:10:55 50.186.180.191 50648 SERVER.IP.ADDRESS 80 - - - - - Timer_ConnectionIdle -

Here is a similar situation but it did not help me.

UPDATE: When i checked the IIS logs, i see some issues like these;

cs-method   cs-uri-stem                     sc-status   sc-win32-status     time-taken  cs-version
POST        /webservice/webservice.asmx     400         64                  46          HTTP/1.1
POST        /webservice/webservice.asmx     400         64                  134675      HTTP/1.1
POST        /webservice/webservice.asmx     400         64                  37549       HTTP/1.1
POST        /webservice/webservice.asmx     400         64                  109         HTTP/1.1
POST        /webservice/webservice.asmx     400         64                  31          HTTP/1.1
POST        /webservice/webservice.asmx     400         64                  0           HTTP/1.1
POST        /webservice/webservice.asmx     400         64                  15          HTTP/1.1

sc-win32-status 64 : The specified network name is no longer available.

sc-status 400 : Bad request

Also some requests takes around 130 seconds, but some of less than 1 second. This is a windows application which connects to a web service for process some data. There is not a query takes around 130 seconds on the database.