title: MQTT - Publish a message to many independent topics
body: <p>In MQTT, A Client can subscribe to a Topic Name or a Topic Wildcard. A message can be  published to a topic or some topics with the same wildcard. But how to publish a message to some topic which are independent to each other? Do I need to modify MQTT Protocol?</p>
  
  <p>For Example: My server handle connections from 10 clients(these client do not relate to each other) with the ids : client1, client2, ..., client 10, and client1 want to send a message to an arbitrary number of clients(e.g. client 3, client 7, client8)</p>