XML-RPC is a standard network protocol that computers can use to talk to each other in a remote procedure call fashion. Remote procedure call essentially means that a program on one computer runs a program on another computer. But a simpler way of looking at this kind of network protocol is just that you have clients and servers. A client makes individual isolated requests of a server. A server sits around waiting for a request to arrive from some client, does what the request asks, and sends a response. It then goes back to waiting for the next request.Here are some examples of remote procedure call (RPC) style communications: There is a server that can measure atmospheric temperature. A client anywhere in the world can ask the server at any time what the temperature is. The "what temperature...