simple VRPN question

[mjabon]

Hello. We have a problem doing the most simple thing with VRPN, which is tracking just one light on the head to move you through the world. In our old code we simply wrote:

viz.go(viz.PROMPT | (viz.HMD + viz.STEREO + viz.TRACKER))
if viz.get(viz.TRACKER):
	PORT_PPT = 1
	viz.cursor(viz.OFF)
	viz.mouse(viz.OFF)
	ppt = viz.add('vizppt.dls')
	#Average over 5 samples
	ppt.command(5,'',5)
	isense = viz.add('intersense.dls')
	viz.tracker()
	#Set eyeheight to zero since we are getting it from the tracker
	viz.eyeheight(1.9)

That is all we had to do.

I tried replacing it with this:

vrpn = viz.add('vrpn7.dle')
ppt = vrpn.addTracker('PPT0@HOSTNAME', 0)

Where hostname is the ip of our PPT machine. However, nothing tracks - ie the person does not move through the world. We don't get errors, the person just does not move.

Any ideas?
Maria