RPC is a concept - not a protocol. For instance, the implementation of RPC I use looks like: POST /v1/:method A JSON object in the request body is the on

RPC is a concept - not a protocol. For instance, the implementation of RPC I use looks like: POST /v1/:method A JSON object in the request body is the only parameter on the method. The response body is the returned value encoded as JSON. Very simple, and still entirely within HTTP. Just not RESTful.