Saturday, August 29, 2009

Fiddler + WCF SOAP+ Cassini = Ooof!

What a PITA trying to observe my DevForce Silverlight application running in Cassini using Fiddler2. Thanks to John Papa I’ve got that working now.

Here’s the situation:

  • DevForce communicates using WCF SOAP service
  • I’m running both the client and the service in Cassini, not IIS
  • Tried all the recommended configurations (see below)

The problem is the WCF SOAP service. There is no issue with REST.

What Finally Worked

Can’t make it work with IE at all. Haven’t found anyone who knows how.

But I can make it work with FireFox … and I am fine with running in Firefox. Here ya go:

  1. Install Firefox (duh)
  2. In fiddler: Tools / Fiddler Options / General / disable IPv6 [may not be necessary]
  3. In fiddler: Tools / Fiddler Options / Connections. Click “Copy Browser Proxy Configuration URL” … which puts the right phrase in your clipboard
  4. In Firefox: Tools / Options / Network / Settings. Click “Automatic proxy” radio button which enables the text box. Paste script address from your clipboard.
    On Vista/Win 7, the address looks like
  5. Remember to “OK” your way out of the dialogs (yes, I forgot this and hit cancel)
  6. Close Firefox
  7. Re-launch Firefox
  8. Re-launch Fiddler
  9. Confirm Firefox browser actions show up in Fiddler
  10. Launch your app
  11. Paste app address into Firefox

What Works If I Change Requirements

You can deploy the server to IIS and point the Silverlight Client at it. That’s fine … but I didn’t want to bother with that. Just want Cassini to do it all.

You can use Nikhil’s excellent IE plug-in, Web Development Helper. This works too. You enable it from the IE menu: View / Explorer Bars / Web Development Helper.  But I was looking for a Fiddler solution.

What Doesn’t Work

Don’t have VPN running. The minute I’m running my VPN, Fiddler stops listening to all IE traffic, even regular browser traffic (no problem for Firefox though). I’m sure there is a way around this. I don’t know what it is … and at the moment it is just easier to shut down my VPN.

Many kind people offered suggestions … all of which failed me one way or another:

  • localHost.:port/myapp (that’s with a period between “localhost” and colon) - app crashes, unspecified service security exception
  • instead of localhost - app crashes, unspecified service security exception
  • ipv4.fiddler:port/myapp instead of localhost - app crashes, unspecified service security exception (because translates to
  • myMachineName:port/myapp instead of localhost – “[Fiddler] Connection to ward-xps failed.
    Exception Text: No connection could be made because the target machine actively refused it”
  • Fiddler proxy setting: Tools / Fiddler Options / General / uncheck “Enable IPv6” – no help
  • Fiddler Tools / WinINET Options / LAN Settings. “Use a proxy server” checked. Click Advanced button … proxy addresses are set to – no help

Many of these suggestions are variations on the cryptic paragraphs in the configuration FAQ on the Fiddler site:


Paul DeFrees said...

Interesting. I was using the ipv4.fiddler option for quite a while without any problems... well, other than the fact that I had to click through several DevForce messages because the server settings in my web project didn't match my app.config in the Silverlight projects. I just made sure the remoteBaseURL pointed to ipv4.fiddler and I also specified a specific start URL in the web project.

I just got tired of having to click through the messages, so I went ahead and set up IIS to host and now that's gone. It would be nice if there was some configuration for the addin to specify whether or not to receive these "helpful" messages. ;)

Ward Bell said...

Interesting, Paul.

Would you please email me with the app.config, webconfig and web project settings? I know what you mean about that message ... it's wrong, it's annoying, and I'll get to the bottom of it.

Email address (munged to avoid spambots) is "AskWard at ideablade dot com"