how the AsyncMessenger work.
AsyncMessenger implements Message
//ouput message
DispatchQueue::start => dispatch_thread.create("ms_dispatch") => DispatchQueue::entry() => Messenger::ms_deliver_dispatch
=> range dispatchers, call Dispatcher::ms_dispatch2
take DaemonServer for example.
DaemonServer implements Dispatcher, add Messenger as its member,
call add_dispatcher_tail(this)
=> DaemonServer:: ms_dispatch2
//input message
ProtocolV2::handle_message => AsyncConnection::dispatch_queue
=> DispatchQueue::enqueue
or => DispatchQueue::fast_dispatch
constructure
