code: public void unsubscribe( String name, Listener l ) {
      synchronized (_listeners) {
        List list = (List)_listeners.get( name );
        if (list != null) {
          list.remove( l );
          if (list.size() == 0) {
            unsubscribe( name );
          }
        }
      }
    }
docs: Unsubscribe a single listener from a channel.  This does not
  send a message to the server unless the listener is the only
  listener of this channel.
  
  @param name The name of the channel to unsubscribe from.
  @param l The listener to unsubscribe