For Windows:
Go to Wifi Settings.
Select the network you are currently connected to.
Go to properties.
see ipv4 address or whatever the ip version of your network.
copy the ip and add the port to it like this:
192.168.12.102:5500
open it on your mobile, and there you go.
PS: I'm on windows and connected to my mobile hotspot, i.e both the laptop and the smartphone is connected to the same network. Let me know if it works for you.
source here.