The remoting functionalities of RTAI-XML are implemented through an XML-RPC server waiting for incoming calls on a specific network port.
As stated in the official web site, XML-RPC is a
spec and a set of implementations that allow software running on
disparate operating systems, running in different environments to make
procedure calls over the Internet. It's remote procedure calling using
HTTP as the transport and XML as the encoding. XML-RPC is designed to
be as simple as possible, while allowing complex data structures to be
transmitted, processed and returned.