Unable to see web page of PC localhost through my (Android) phone (all linked to zerotier)

there’s a web page (dynmap of minecraft server) at localhost:8123 or xxx.xxx.xxx.xxx:8123 (ipv4) of PC-1, I can see this web page on PC-2 browser (linked to zerotier) with URL xxx.xxx.xxx.xxx:8123, yet I can’t do the same on my Android phone browser, which was also linked to zerotier and URL was also xxx.xxx.xxx.xxx:8123. I couldn’t figure out what’s wrong and I wonder how would I be able to solve this problem. thanks if you can offer your help.