Is messageEncoding="Text" Applied for WCF Request

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WCF

encoding

text

WebSockets

I wrote a WCF service and a WCF client application in .NET 4.5. They communicated each other using WebSocket and worked very well. As we know, Binary SOAP message encoding was used by default. But I changed it to Text SOAP message encoding for some purpose. The service and application still worked well after the change. Then I used Microsoft Network Monitor 3.4 (NetMon.exe)  to check the messages. Strangely, I found all Request messages were still encoded while all Response messages were Text messages which I wanted.
Could someone please tell me what happened?
P.S. The WCF service's web.config is as the following code piece:

<system.serviceModel>
    <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="true"/>
        </behavior>
      </serviceBehaviors>
    </behaviors>
    <protocolMapping>
      <add scheme="http" binding="netHttpBinding" bindingConfiguration="textWSHttpBinding"/>
      <add scheme="https" binding="netHttpsBinding" bindingConfiguration="textWSHttpsBinding"/>
    </protocolMapping>
    <bindings>
      <netHttpBinding>
        <binding name="textWSHttpBinding" messageEncoding="Text"/>
      </netHttpBinding>
      <netHttpsBinding>
        <binding name="textWSHttpsBinding" messageEncoding="Text"/>
      </netHttpsBinding>
    </bindings>
    <serviceHostingEnvironment aspNetCompatibilityEnabled="true" multipleSiteBindingsEnabled="true" />
</system.serviceModel>

The app.config of the WCF client application is as the following code piece:

<system.serviceModel>
    <bindings>
        <netHttpBinding>
            <binding name="NetHttpBinding_IWSChatService" messageEncoding="Text">
                <webSocketSettings transportUsage="Always" />
            </binding>
        </netHttpBinding>
    </bindings>
    <client>
        <endpoint address="ws://localhost/WcfWSChat/WSChatService.svc"
            binding="netHttpBinding" bindingConfiguration="NetHttpBinding_IWSChatService"
            contract="WSChatServiceReference.IWSChatService" name="NetHttpBinding_IWSChatService" />
    </client>
</system.serviceModel>

The screenshot of the Request body in NetMon.exe is as the below:
Request Body[^]
The screenshot of the Response body in NetMon.exe is as the below:
Response Body[^]