How do ROSJAVA nodes communicate between threads rather than processes?

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As we all know,ROS Nodes communicates via XMLRPC and TCP. But in ROS JAVA, nodes are executed in different threads rather than different processes, so how can they hava different addresses? I am thinking that different processes can be assigned different port but different threads can not. So it's confusing how nodes communicate via TCP/XMLRPC with different uris or addresses.
I'm also confused about AdvertiseAddress and BindAddress. Why would an XMLRPC Server have 2 addresses? What's the difference? Really appreciated if anyone can help. :)