Help with MFRC 522 RFID project intergating to local Mysql

Apperently not consistently as im using my mobile hotspot(thinking it can work the same as a wifi connection?)

I get the IP adress from the ethernet adapter Ethernet (comes from the connection from the rj45 slot of shield to laptop). This one I use for the codes where IP of computer is needed.

And for the DHCP for the codes that require IP of arduino which I cannot generate consistently, due to me test using my mobile hotspot(thinking it can be an alternative for a wifi generated by a router?)

Im just still testing the waters on the posts I saw and testing out their codes but none specifically cater to my situation. Yes I use "localhost" or the "127.0.0.1" when needed to, but its still not clear to me for the other parts.

What are my options on connecting my project without the router? Im seeking more of a LAN connection locally. I tried searching for similar project but none cater to my situation(no router no wifi, just plain connectivity over xampp).Any ideas would be much appreciated.