Implementing Http Callbacks in a plugin allows that plugin to repond directly to callback requests.
IHttpCallback
The IHttpCallback interface has the following members:
void ProcessRequest(HttpContextBase httpContext);
The ProcessRequest method is used to handle calls to the handler.
void SetController(IHttpCallbackController controller);
The SetController method offers access to the IHttpCallbackController. The controller is necessary to generate the url to access the IHttpCallback.