The quick answer is no. When you send messages from server to client,
things will always be in order. Sending from client to server however, the
only transport that queues outgoing client to server calls is websockets.
With persistent connections you're out of luck when trying to order
sends from client to server as there's no way to know when the send is
complete. Hubs on the other hand return a deferred (and task in C#), which
lets you wait on the send to complete before sending again.