A functionality of one of the products I’m working on suddenly stopped working without any code changes on our side. Our application connects to a web service to get some data and that no longer worked, our customers getting the following error in their logs “The underlying connection was closed: An unexpected error occurred on a send.” The first thing to do was checking whether the web service was still up and running as expected. The requests made with SoapUI or Postman were all successful, so it was actually something in our application that was actually wrong. So I decided to use Fiddler to look at how our requests look and what do we get back.

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