To get this, you could use an HTTP sniffing tool like Fiddler or HTTPFox, but there may be times that you have problems with this due to proxies etc being used in the company.
Thankfully there's a way to output the trace using the code below:
<system.diagnostics>
<trace autoflush="true"/>
<sources>
<source name="System.Net" maxdatasize="1024">
<listeners>
<add name="TraceFile"/>
</listeners>
</source>
<source name="System.Net.Sockets" maxdatasize="1024">
<listeners>
<add name="TraceFile"/>
</listeners>
</source>
</sources>
<sharedListeners>
<add name="TraceFile" type="System.Diagnostics.TextWriterTraceListener" initializeData="trace.log"/>
</sharedListeners>
<switches>
<add name="System.Net" value="Verbose"/>
<add name="System.Net.Sockets" value="Verbose"/>
</switches>
</system.diagnostics>
Acknowledgements to the following post:
http://stackoverflow.com/questions/300674/getting-raw-soap-data-from-a-web-reference-client-running-in-aspnet