Have you taken a look at the servicemix-wsn2005 example scenario here:
Notice the message requests and the responses. I'm not a WSN expert, but it seems like you've left out some steps:
1) You must send the message.
Have you done all of these steps?
Thanks. I just tested the example-scenario you had referred using pull points and it works fine. But I want to use the approach of asynchrnous notifications. With pull points, the consumer is polling to see if there are new messages. If I am not mistaken, this is only an option and not the common behavior of WSN. Once a consumer registers an endpoint to the broker, the broker should send the message directly to the consumer. By running the example of createpull points, I can see that the problem is not in the broker but in my consumer subscription endpoint. So I changed my receiver to follow the http://servicemix.apache.org/pojo-support.html MyReceiver example and I can get the data now.