Trace WCF communication in Fiddler

Add following in your web.config file. makes sure that fiddler proxy port (8888) is correct. (in Tools --> Options --> Connections)

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