A real luxury we have is a smartphone hotspot. No matter where we are in the USA, if there is cellular service of 3G or 4G or LTE we have internet. Ok, so you have a hotspot and have internet. To most that means cruising the internet and port 80 is the only port you need to have for normal internet browsing. However, if you want more that is where the problems start.
Most providers do not allow the user to open ports on the cellular system. For one particular ham radio system, IRLP, you need to have several ports opened up. For FTP you need port 21 and for SSH you generally need port 22 but these are shut down by the provider and they open them only if they want to open them and that is never. Other special applications require a multitude of other ports from 1 - 50,000+.
There is a solution and it is called VPN (virtual private network). You can make this system yourself or you can lease one by the month or year (nominally, $15 per month). If you make your own you will need a "VPN Server" and a fixed IP address from which to generate the tunnel that has whatever ports you want open and this is beyond the casual lay persons efforts. Here is a list of 5 options and even an intro on a DIY but if this link goes bad just Google VPN Service Providers.
If you really need help then you can contact me via my Facebook link. I will add several more articles on what to connect with your new tunnel under the banner "A Cruiser's Luxury".