code: public boolean register( String clientID , String subscriptionName )
  	{
  		String key = clientID+"-"+subscriptionName;
  		synchronized (subscriptions)
  		{
  			if (subscriptions.containsKey(key))
  				return false;
  			
  			subscriptions.put(key, new DurableTopicSubscription(System.currentTimeMillis(),
  					                                            clientID,
  					                                            subscriptionName));
  			return true;
  		}
  	}
docs: Register a new durable subscription
  @param clientID
  @param subscriptionName