Send a message to a message handler within the same session.
The Scope Parameter
It is important to be mindful of the scope parameter when calling this function. It is possible to have multiple instances of a view open in a single page, thus invoking the function with a value of "page" for the scope parameter (or omitting the parameter) will invoke the message handlers on all valid message types. This advice is also applicable when the scope parameter value is passed as "session", as all instances of the matching message type in the whole session will be called.