Fiddler to the Rescue

Last week I was working on a Sliverlight 1.1 article for the Visual Basic DevCenter (http://msdn2.microsoft.com/en-us/vbasic/default.aspx)  and ran into some problems making my Silverlight application communicate with a web service I included in my examples.

After some discussion with Rick Strahl (www.west-wind.com/weblog) he told me to use Fiddler to diagnose my problem. Fiddler is a free HTTP sniffer that can be found at http://www.fiddlertool.com/fiddler/

Fiddler is a tool that “sniffs” all HTTP traffic by inserting a proxy between the WinInet stack your web calls.  The proxy then outputs its results to a very cool windows application that will display your traffic real time. The following screen shows the output of the current version of fiddler.

After installing Fiddler it took me all of 5 minutes to see that I was not properly flushing a send buffer resulting in a bunch of “500” results calls. I added a single line of code and my code was working properly.

On item of note Fiddler will not trace calls made to 127.0.0.1 or localhost. If you are debugging local applications you will need to address them via your machine name.