Hi @thomaswang, thanks for your query. Firstly, it is worth mentioning that the Stream Engine API is designed for advanced level use and experienced developers so if you are looking for a simple solution to extract eye tracking data for interaction purposes then it may be more beneficial for you to check out the interaction library API which you can download @ https://developer.tobii.com/consumer-eye-trackers-interaction-library/
Unless you have a specific need to use the Stream Engine, please try this alternative and let us know how you get on. Best Wishes.