servicemix ws-notification doesn't support async messaging ?

[Zhao Jerry-JZHAO2]

Dear Sir/Madam,
 
I am considering to use Servicemix ws-notification for the following use
cases:
 
       Client1 (JAVA code) --> send message to Topic
       Client2 (C++ code) <--- Get message from Topic
       Client3 (C++ code) <--- Get message from Topic
       Client4 (C++ code) <--- Get message from Topic
 
I hear of bad news that ServiceMix ws-notification doesn't support async
messaging over HTTP.  For the above use case, client2/3/4 have to do
periodically polling the ServiceMix bus to check whether any data
available for a particular topic. This would result in performance
issues. 
 
By the way, Client2/3/4 are developed with C++. We don't consider to use
RMI.
 
If this bad news is true,  do you know when ServiceMix ws-notification
will support async messaging over HTTP.
If this bad news is not true,  what is the solution to implement async
messaging over HTTP.
 
Any suggestion/feedback is really appreciated.
 
Thanks,
Jerry