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The Gateway Exchange Protocol (GEP) Subscription Tester is a tool used to validate that a GEP subscription based connection is working as expected. It can also be used to validate filter expressions that can be used to select a set of points in the openPDC and other GPA synchrophasor products, e.g., SIEGate for use as inputs or outputs for any adapter.

The application is a simple graphical program that uses the Grid Solutions Framework Unity subscription API to display trending lines for each subscribed measurement in the specified filter expression. Trend lines are updated as values are received in real-time. Mouse controls (or finger gestures) will allow rotation and zoom, arrows keys will adjust X/Y location. Clicking on the "Subscription Controls" area at the bottom of the screen will pop-up a control window to allow you to change connection information (e.g., server/port to connect to), the filter expression and even replay data if a historian is enabled.

See [usage documenation](https://github.com/GridProtectionAlliance/openPDC/blob/master/Source/Documentation/wiki/GEP_Subscription_Tester.md)