SOAP is a W3C recommended protocol for message exchange using XML over various transport layers. Specifications can be found here. The Join implementation of SOAP web services only used the HTTP transport layer. It uses the XFire stack to expose its APIs through SOAP.
These are some parameters and details on how to call SOAP web services:
http://host[:port]/[context]/remoting/xfire/[service]
,http://host[:port]/[context]/remoting/xfire/[service]?WSDL
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