为什么WSHttpBinding会创建四个Fiddler会话？

Question

请参阅以下代码：

Windows表单应用

//WindowsFormsApplication1.cproj
    namespace WindowsFormsApplication1
    {
        public partial class Form1 : Form
        {
            public Form1()
            {
                InitializeComponent();
                ServiceReferenceInsecure.IService1 s1 = new ServiceReferenceInsecure.Service1Client("WSHttpBinding_IService1");
                string name1 = s1.HelloWorld("Ian"); //5
             }
        }
    }



  <system.web> 
  <identity impersonate="true" />
  <authentication mode="Windows" />    //App.config
    <?xml version="1.0" encoding="utf-8" ?>
    <configuration>
    </system.web>

  <system.net>
    <defaultProxy useDefaultCredentials="true">
      <proxy
              usesystemdefault="True"
              bypassonlocal="False" />
    </defaultProxy>

  </system.net>

  <startup> 
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
    </startup>
  <system.serviceModel>
    <bindings>
      <basicHttpBinding>
        <binding name="BasicHttpsBinding_IService1">
          <security mode="Transport" />
        </binding>
      </basicHttpBinding>
      <wsHttpBinding>
        <binding name="WSHttpBinding_IService1" />
      </wsHttpBinding>
    </bindings>
    <client>
      <endpoint address="https://hq-wk-is.lincspolice.local/WCFSSL/Service1.svc"
        binding="basicHttpBinding" bindingConfiguration="BasicHttpsBinding_IService1"
        contract="ServiceReferenceInsecure.IService1" name="BasicHttpsBinding_IService1" />
      <endpoint address="http://hq-wk-is:86/WCFSSL/Service1.svc" binding="wsHttpBinding"
        bindingConfiguration="WSHttpBinding_IService1" contract="ServiceReferenceInsecure.IService1"
        name="WSHttpBinding_IService1">
        <identity>
          <userPrincipalName value="3212627@lincspolice.local" />
        </identity>
      </endpoint>
    </client>
  </system.serviceModel>
</configuration>

服务1

 //Service1.svc.cs
        public class Service1 : IService1
            {
                public string HelloWorld(string value)
                {
                    return "Hi " + value;
                }

            }

//Web.Config
?xml version="1.0"?>
<configuration>

  <system.net>
    <defaultProxy>
      <proxy
              usesystemdefault="True"
              bypassonlocal="False" />
        <!--<proxy bypassonlocal="False" usesystemdefault="True"  />-->
    </defaultProxy>
  </system.net>

  <appSettings>
    <add key="aspnet:UseTaskFriendlySynchronizationContext" value="true" />
  </appSettings>
  <system.web>
    <compilation debug="true" targetFramework="4.5" />
    <httpRuntime targetFramework="4.5"/>
  </system.web>
  <system.serviceModel>
    <bindings>
      <basicHttpBinding>
        <binding name="BasicHttpBinding_IService2" />
        <binding name="BasicHttpsBinding_IService2">
          <security mode="Transport" >
            <transport clientCredentialType="Windows" />
          </security>
        </binding>
      </basicHttpBinding>
    </bindings>
    <client>
      <endpoint address="http://hq-wk-is:86/WCFSSL2/Service2.svc" binding="basicHttpBinding"
        bindingConfiguration="BasicHttpBinding_IService2" contract="ServiceReference1.IService2"
        name="BasicHttpBinding_IService2" />
      <endpoint address="https://hq-wk-is.lincspolice.local/WCFSSL2/Service2.svc"
        binding="basicHttpBinding" bindingConfiguration="BasicHttpsBinding_IService2"
        contract="ServiceReference1.IService2" name="BasicHttpsBinding_IService2" />
    </client>
    <behaviors>
      <serviceBehaviors>
        <behavior>
          <!-- To avoid disclosing metadata information, set the values below to false before deployment -->
          <serviceMetadata httpGetEnabled="true" httpsGetEnabled="true"/>
          <!-- To receive exception details in faults for debugging purposes, set the value below to true.  Set to false before deployment to avoid disclosing exception information -->
          <serviceDebug includeExceptionDetailInFaults="false"/>
        </behavior>
      </serviceBehaviors>
    </behaviors>
    <protocolMapping>
      <add binding="basicHttpsBinding" scheme="http" />
      <add binding="wsHttpBinding" scheme="https" />
    </protocolMapping>    
    <serviceHostingEnvironment aspNetCompatibilityEnabled="true" multipleSiteBindingsEnabled="true" />
  </system.serviceModel>
  <system.webServer>
    <modules runAllManagedModulesForAllRequests="true"/>
    <!--
        To browse web app root directory during debugging, set the value below to true.
        Set to false before deployment to avoid disclosing web app folder information.
      -->
    <directoryBrowse enabled="true"/>
  </system.webServer>

</configuration>

当我运行此代码时;我看到了预期的结果。但是，当我回顾Fiddler时，我会看到如下所示的四个会话：

为什么WSHttpBinding有四个会话？我使用BasicHttpBinding时只有一个会话。