wcf NetworkCredential with empty user name and password

Question

I created a WCF service and the security mode has been set to Transport and ClientCredentialType is Windows. Below is my client side code:

NetTcpBinding binding = new NetTcpBinding();
binding.Security.Mode = SecurityMode.Transport;
binding.Security.Transport.ClientCredentialType = TcpClientCredentialType.Windows;
binding.Security.Transport.ProtectionLevel = System.Net.Security.ProtectionLevel.EncryptAndSign;

ChannelFactory<IServices> factory factory = new ChannelFactory<IServices>(binding, service);
NetworkCredential credential = factory.Credentials.Windows.ClientCredential;
credential.UserName = string.Empty;
credential.Password = string.Empty;
IServices connect = factory.CreateChannel();
bResult = connect.IsServerOnline();

Server config:

<system.serviceModel>
    <bindings>
      <netTcpBinding>
        <binding name="tcpConSecure" />          
          <security mode="Transport">
            <transport clientCredentialType="Windows" protectionLevel="EncryptAndSign" />
          </security>
        </binding>
      </netTcpBinding>
    </bindings>
    <services>
      <service name="TestService.Services">
        <endpoint address="tcp" behaviorConfiguration="EndpointBe" binding="netTcpBinding" bindingConfiguration="tcpConSecure" contract="TestServiceInterface.IServices" />
      </service>
    </services>
</system.serviceModel>

In theory, I should input the correct windows account name and password, but during test, I found I could set the UserName and Password as empty, and channel still could be created. Why?
Client and Server are not on the same machine, but they are in same domain. The logon account of Client machine could login Server machine. In this case, I could use empty user name and password to create connection and call WCF service.

Answer 1

The channel factory created by the client has nothing to do with the WCF server. Even if the server closes the client, the channel factory can be created successfully, but an error will occur when the method is called.

If you only create a channel, then you set the Username and Password in the credential has nothing to do with the WCF Service. Only when the call is made, the client will pass the Username and Password to the server, and the value of Username and Password will be verified.

This is the explanation in the Microsoft documentation:

UPDATE:

There is another possibility that can cause this problem. If the client and server are on the same machine, the client does not need to provide windows credentials.