How to debug/trace System.Web.Services.Protocols.SoapHttpClientProtocol.invoke (from Windows mobile)?

Question

I am trying to call web service from C# application but I am getting exception:

InvalidOperationException 
client found response content type of 'text/html; charset=utf-8', but expected 'text/xml'

How can I see the request and reponse messages un URL? My service runs on Desktop, but client runs on Windows Mobile CE 6.x, mobile device is connected to the Dektop using usb. Probabily that is the reason why I don't see the HTTP traffic in Wireshark or Fiddler (I have tried both). The service works - I can check it using Postman (method returns correct and meaningful result XML).

Answer 1

You can turn on the debug on some of the libraries that internally make the HTTP calls (in my case, they are HTTPS, so inspecting via wireshark is impossible).

You should add to your app.config:

<system.diagnostics>
    <trace autoflush="true"/>
    <sources>
      <source name="System.Net" tracemode="protocolonly" 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"/>
    </switches>
</system.diagnostics>

This will add a trace.log where your exe runs. If you don't know where your service is running, you should be able to put a non-relative path.

Also, this adds the same logs when running the code inside Visual Studio, in the output window (not the output console).

P.S.: You can change the log level to "Information" if you just need the headers of the request and responses and information on opening and closing connection.

Answer 2

Okay, this is going to sound weird, but are you using Default Document within IIS? I know this probably shouldn't be the case, but when I set up a default document for my web service's site, and pointed my ServiceReference to the shortened address, it was able to run... but only locally. Otherwise, I'd get that same "Html instead of XML" error.

The fix in my case was to no longer refer to the shortened URL in the service reference, and type out the full URL (aka, not using the default document property for the site.)

Answer 3

The easiest and best way to debug a SOAP client is to create a SOAP extension that logs the SOAP messages sent to and from a Web service or Web service client.

Codeproject has a good tutorial how to do this properly: Efficient Tracing Using SOAP Extensions in .NET

And here is a shorter MSDN article: How to: Implement a SOAP Extension

There are also commercial SOAP Debuggers out that are worth the money, like the XML Spy SOAP Debugger or SOAPSonar which does validation and invocation.

BTW: If you would use PHP or Java you would basically use the same approach.