1. A long connection time (5~15 seconds) of BLE for dual mode chip is needed.
Stop and restart the App again if the connection time is too long (>30 seconds).
2. Known Transparent (UART) Service:
Nordic UART Service: tested.
ISSC Transparent Service: tested.
HM-10 : listed, but not tested yet.
The King of GUID application is a free utility with ads for Android devices allowing individual highly unique GUID/UUIDs to be created.