I practically want to simulate a GPS
GpsGate standard has an embedded GPS simulator (the is a 14 days trial version). You can provide a list of GPS coordinates and it will fetch them to any NMEA compatible application by providing a virtual serial port to it and sending these coordinates to the application.
But when S&T works, if you provide a few GPS coordinates, you may end up driving not on expected streets road in Streets and Trips . You will have to provides many close GPS coordinates so S&T appears to stay on the road while simulating. In normal S&T operation, it will try to hold on the nearest road of the current GPS coordinate...