Using SOAP Monitor for external clients not working

I have a .Net WCF web service using BasicHttpBinding.
I can call that web service from SOAP UI and an external client easily.
But I want to use the SOAP Monitor for an external .Net client that is running on the same machine as the web service.
After starting the monitor as HTTP Proxy (with Setup as global proxy enabled) I can call the web service using SOAP and it is capturing the traffic and I can see the message contents.
But if I use a external client (developed in WCF as well) that is calling the same web service SOAP Monitor is not capturing the traffic. I have set the proxy to the http://localhost:8081 so that traffic passes though SOAP UI Monitor. But it is not working. Is it possible to do what I want and how to configure.

In my client code I have tried

var b = client.Endpoint.Binding as System.ServiceModel.BasicHttpBinding;
b.ProxyAddress = new Uri("http://localhost:8081");
b.BypassProxyOnLocal = false;
b.UseDefaultWebProxy = false;

I also tried in client config file

 <basicHttpBinding>
     <binding name="BasicHttpBinding_CalculatePiService" bypassProxyOnLocal="false"
                           useDefaultWebProxy="false" proxyAddress="http://localhost:8081">
      </binding>
  </basicHttpBinding>