null MessageBroker

My application needs server push.  I am trying to get a simple "Hello World" going, but I can't get past a null MessageBroker.  I simplified my configuration files and it might be my issue.

My services-config.xml

includes only the messaging and data-management configs:

<service-include file-path="messaging-config.xml"/>
<service-include file-path="data-management-config.xml"/>

channels:

<default-channels>
   <channel ref="my_rtmp"/>
   <channel ref="my_amf"/>
   <channel ref="my_polling-amf"/>
</default-channels>

a single server

<server id="my-nio-server" class="flex.messaging.socketserver.SocketServer">

and i left the channel definitions as defined.

My messaging-config.xml is:

<service id="message-service" class="flex.messaging.services.MessageService">
  <adapters>
    <adapter-definition id="actionscript" class="flex.messaging.services.messaging.adapters.ActionScriptAdapter" default="false"/>
  </adapters>
  <destination id="DocumentSessionTopic">
    <properties>
       <network>
          <subscription-timeout-minutes>0</subscription-timeout-minutes>
       </network>
       <server>
          <max-cache-size>1000</max-cache-size>
          <message-time-to-live>0</message-time-to-live>
          <allow-subtopics>true</allow-subtopics>
          <subtopic-separator>.</subtopic-separator>
          <cluster-message-routing>server-to-server</cluster-message-routing>
      </server>
    </properties>
    <channels>
       <channel ref="my_amf"/>
       <channel ref="my_polling-amf"/>
    </channels>
  </destination>
</service>

My java part is:

MessageBroker msgBroker;
msgBroker = MessageBroker.getMessageBroker(null);
msgBroker.start();

msgBroker is null when I try to invoke its start() method.

Thanks in advance.