How to use Fiddler to monitor WCF service

Question

I have a WCF service that accepts a complex type and returns some data. I want to use Fiddler to see what the incoming requests to the service looks like. The client is .net console app which uses a Service reference proxy. Is this possible with Fiddler. I'm new to this tool and have only used it in the past to post data with the request builder.

Answer 1

You need to add this in your web.config

<system.net>
  <defaultProxy>
    <proxy bypassonlocal="False" usesystemdefault="True" proxyaddress="http://127.0.0.1:8888" />
  </defaultProxy>
</system.net>

1. then Start Fiddler on the WEBSERVER machine.
2. Click Tools | Fiddler Options => Connections => adjust the port as 8888.(allow remote if you need that)
3. Ok, then from file menu, capture the traffic.

That's all, but don't forget to remove the web.config lines after closing the fiddler, because if you don't it will make an error.

Reference : http://fiddler2.com/documentation/Configure-Fiddler/Tasks/UseFiddlerAsReverseProxy

Answer 2

Fiddler listens to outbound requests rather than inbound requests so you're not going to be able to monitor all the requests coming in to your service by using Fiddler.

The best you're going to get with Fiddler is the ability to see all of the requests as they are generated by your Console App (assuming that the app generates web requests rather than using some other pipeline).

If you want a tool that is more powerful (but more difficult to use) that will allow you to monitor ALL incoming requests, you should check out WireShark.

Edit

I stand corrected. Thanks to Eric Law for posting the directions to configuring Fiddler to be a reverse proxy!

Answer 3

Just had this problem, what worked for me was to use localhost.fiddler:

 <endpoint address="http://localhost.fiddler/test/test.svc"
            binding="basicHttpBinding" 
            bindingConfiguration="customBinding" 
            contract="test" 
            name="customBinding"/>

Answer 4

Consolidating the caveats mentioned in comments/answers for several use cases.

Mostly, see http://docs.telerik.com/fiddler/Configure-Fiddler/Tasks/ConfigureDotNETApp

• Start Fiddler before your app

• In a console app, you might not need to specify the proxyaddress:

  <proxy bypassonlocal="False" usesystemdefault="True" />
  

• In a web application / something hosted in IIS, you need to add the proxyaddress:

  <proxy bypassonlocal="False" usesystemdefault="True" proxyaddress="http://127.0.0.1:8888" />
  

• When .NET makes a request (through a service client or HttpWebRequest, etc) it will always bypass the Fiddler proxy for URLs containing localhost, so you must use an alias like the machine name or make up something in your 'hosts' file (which is why something like localhost.fiddler or http://HOSTNAME works)

• If you specify the proxyaddress, you must remove it from your config if Fiddler isn't on, or any requests your app makes will throw an exception like:

  No connection could be made because the target machine actively refused it 127.0.0.1:8888

• Don't forget to use config transformations to remove the proxy section in production

Answer 5

So simple, all you need is to change the address in the config client: instead of 'localhost' change to the machine name or IP