Simple client identification in WCF

I'm using a self-hosted WCF service with duplex tcp binding without any kind of security. I'd like to transport a username and password from the client so the server code can check for validity. How do I do that? The main goal is to keep it simple.

My idea was to set the binding.ClientCredentials property when establishing the connection, but I don't see how I can access these properties in 开发者_运维问答the server code.