void deviceAdded (Device dev, DefaultTreeModel model)
    throws IOException
    {
	HubNode		h = getHubOf ("add", dev);

	if (h == null) {
	    System.err.println ("what hub has " + dev);
	    return;
	} else if (h != this) {
	    h.deviceAdded (dev, model);
	    return;
	}
	

	synchronized (children) {
	    for (int i = 0; i < last; i++) {
		if (children [i].dev == dev)
		    return;
	    }
	    children [last] = createTreeNode (dev);
	    if (trace)
		System.err.println ("HubNode "
		    + addr
		    + " add child " + last
		    + ", addr " + dev.getAddress ()
		    );
	    if (model != null)
		model.nodesWereInserted (this, new int [] { last });
	    last++;
	}
    }