ask your ISP to give you a static ip adress or you can use a VPS to be able to gain a static ip
a ip is assigned by the ISP , depending on isp is it static (always same ip) , Semi static (rotation betwean 2+ ip's ) or variable ( changing betwean a big range )
then it can depends on the settings the isp have if it change every time your browser opens ?? , every time you restart your pc or everytime the router get changed or on a fixed time ( 1x a day ?? 1X a week ?? 1X a month )
those are called variable ip's (dynamic ip's )
the only way to solve it is by 1) manual assigning the ip's (if you got 2+ static ip's where it switch betwean) or by contacting your ISP
please note , your ISP can charge you money to make your ip static
if that fails , then you can hire a vps server (virtual private server)
but a vps is not free/cheap , so it is something to think about
as a other option you can use hamachi , but hamachi is a vpn ( Virtual Private Network)
that means that every1 need to be in the same network to be able to find you
hopely this can help you
Greetings From PowerChaos