Fluke and space invaders input ports

hi all.. i have a weird board here... withotu going into details, i want to read the input ports, i can't figure out the darn mame source driver to find where the input ports are, but i gather they are on actual ports, not in addresses.. i'm not entirely familiar with the 8080 and how it works, and this is the first time i have had wanted to read the ports... on other cpus (z80 for example,) i just read and interperet an address... hwo do i do this with the 8080 in space invaders?? BTW i'm using a 9100 :) thanks! andy