XML-RPC is a web services protocol that implements remote procedure calls over HTTP. While it doesn't have the advanced feature set of SOAP or CORBA, its simplicity makes it easy to implement and use.
This chapter introduces the main concepts and limitations of XML-RPC, and describes how XML-RPC uses XML and HTTP. If you plan to use a toolkit, you need to read only the first part of the chapter about the concepts in XML-RPC. If you're going to do it all yourself, read not only the concepts sections but also the XML and HTTP sections, and the sample client section about the Meerkat service.