Can a WCF service provide publish / subscribe to a Linux based C ++ client application?

I have a WCF service written to provide specific functionality to intranet based clients. This is easy when the client is running Windows. I want to implement the same functionality for my Windows clients that is available for my Linux clients. My questions?

How can I communicate with a linux C ++ based client (which supports post callbacks)? I know using SOAP over HTTPBinding, but is this the only way (doesn't support callbacks, which I believe)?

Will this apply if I use TCPBinding on the service side? The service is currently configured using TCP, but what are my options for communicating with a linux client?

I read somewhere that messages can also be sent (via web services, which I assume) in XML and not SOAP? What would be the best approach, or how to determine which one is the best fit?

I am trying to understand the options I would have for a WCF data service if I wanted to communicate with it from a linux client. I appreciate your help.

Thank,

Jeremiah