WCF Tracing. How I can get the exact reason for closing connection?

Question

In my WCF service, when trying transfer large data I constantly get an error: The underlying connection was closed: The connection was closed unexpectedly

Answer 1

I've spent the last 2+ days trying to find why I'm getting "The underlying connection was closed: The connection was closed unexpectedly" with a method call returning with more data vs when not so much data (i.e., it works ok with smaller sets of data being returned only).

My error messsages are slightly different (perhaps due to framework differences) but wanted to share the cause I found. First, I would like to state that while tracing and increasing the sizes of certain things in config files given as answers above may be helpful for tracking down WCF errors, these things did nothing to help me determine the real cause of the error.

By just looking at the exception thrown and up the chain, I could see the following root, error: "An existing connection was forcibly closed by the remote host" - this was a System.Net.Sockets.SocketException

Going up the call chain then was: "Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host." - a System.IO.IOException, then

"The underlying connection was closed: An unexpected error occurred on a receive." - a System.Net.WebException, then finally what was the caught exception's message,

"An error occurred while receiving the HTTP response to . This could be due to the service endpoint binding not using the HTTP protocol. This could also be due to an HTTP request context being aborted by the server (possibly due to the service shutting down). See server logs for more details." - a System.ServiceModel.CommunicationException

The enabling tracing then viewing the trace logs with the TraceViewer did make this easier to see, but never told me the real cause for my "An existing connection was forcibly closed by the remote host" error.

In my case, my WCF service is hosted on IIS6 and only when I contacted our institutional support in charge of these servers and asked them to look in the system event logs, did I immediately see the answer - a System.OutOfMemoryException!

My WCF service runs in an allocated 200MB of RAM and my method was consuming more than this. I looked in my method and found eventually a block of code that should have been outside/below the block (loop) it was in. . ..so I had an exponential type of collection being generated in my method.

Hope this may help others.