Figure 1. Overall concept 

1. Make sure you have latest Infrakit SURVEY app installed to your Android device.

2. Use Topcon TRU software to set Bluetooth PIN to GCX3 (otherwise not possible to connect with BT)

Note that  receiver should have an Options (OAF) that allows RTCM3x correction and writing NMEA to Bluetooth

3. Pair your Android device and GCX3 with Bluetooth. Please check  Sokkia manual for details.

3. In Infrakit SURVEY, configure NTRIP address and mountpoint by selecting "Menu", "Ntrip settings".

Note that NTRIP service should provide RTCM3.2 correction.

4. In Infrakit SURVEY, select "GCX3 Ntrip" as location source by selecting "Menu",  "Select location source". In this mode Infrakit SURVEY sends initialization commands to GCX3 receiver.

Note that no further commands can be sent to receiver without resetting the receiver, since command port is now listening to RTCM messages instead of commands.