If on Windows, go to command prompt (start-run-cmd), or in terminal (if on Linux) and type in
Copy down the first IP address shown
...I went back to my smartphone (connected through router wifi), and entered this:
Put IP as Host Address. I did not specify a port on mine. (Zoiper Premium)
Left Outbound Proxy blank.
In Zoiper--- Config (wheel) --- Connectivity -- Listening Ports -- I unchecked the first port 5060. Left the others checked.
The PC laptop has Zoiper free version. Pretty much the same, except I could enter the Host Address by name; didn't have to put in IP and it works fine.