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I have tried interfacing with Tobii Tx300 with pygaze in linux. But no luck so far. Dummy tracker is working fine.
This is very little information to work with...
I do not use Tobii devices, so I'm quite unfamiliar with them. To be honest, I'm quite surprised they even have a Linux SDK. The only (very generic) reason I can come up with, is that you haven't installed the Tobii SDK and/or the Python libraries that come with it.
If you have installed both of those correctly, I'm going to need more information to be able to pinpoint the issue. Are you getting any error messages at all?