Hello,
Win 98 (and I believe 95 as well) have an option called dialup server.
Just go to the control panel, add remove programs, Windows Setup tab.
In communications you should see dialup server.
It's been a while since I've used this so you'll have to figure out the rest yourself.
I do remember that once it's installed you start the "service" by opening the Dialup Networking Folder in My Computer then clicking on the menu option Tools (I think...) and starting it.
Sorry I can't be more specific. It's been at least 5 years since I've used this.