It takes a lot more that just http. I'd need to know the URL schema if you're restful, or the method names if you're SOAPy. Then there's the format of the data (SOAP, JSON, XML ..) and the expected data fields in the data sent and received, etc.

I don't think it's fully implemented yet, but here's the protocol Appleseed is using:

http://svn.appleseedproject.org/trunk/_documentation/quickso...

From the source, it looks like they're building abstracted PHP libraries, too. And it's an event/hook architecture, so you can pop this protocol out and put another one in, theoretically.

I don't know if this is a placeholder protocol while they build the software, or if this is what they plan on using and evolving.