Unfortunately Nikon does not provide documentation for the WT-5 and it is way out of my budget.
Reading the manual for it I guess in the PC mode it uses PTP/IP protocol for communication like it does with the WU-1a/1b adapter and Nikon models with built in wireless.
After pairing the wireless you could try connect to with the 'Nikon wireless' button.
If the camera IP is other then 192.168.1.1 then you must long press the 'Nikon wireless' button and enter the IP address and press the 'Connect' button.
Thanks very much for your hint. I tried a few settings but none of them works. At least the usb connection is working properly. If somebody reads this blog and has got a working setting with the WT-5 it would be great if he can describe it in detail. Many thanks so far for your work and support.
Can you pls tell me how you got the wired connection to work ?? I connect the nikon d4 with my smartphone, then turn on the kamera. The app starts loads a few seconds and crashes again. Had it working with my nikon d3300