public async bool call_async (string method, Variant? @params, Cancellable? cancellable, out Variant? return_value) throws Error
params on the remote peer.
Upon completion or failure,
callback is executed and it should call call_async.end to complete the
request and release any memory held.
params is floating, the floating reference is consumed.
the name of the method to call
A Cancellable or null
a callback to executed upon completion
A Variant of parameters or null
user data for