Could anyone tell me how to do the following....

I got a macos computer and a netBSD box.....what I'd like to do is
connecting those two together, using a serial cable (printer port to
printer port :) (See below)...then I'd like to be able to dial up on a PPP
connection on the NetBSD and use the internet on both my NetBSD box and the
macos computer (which is using Open Tpt, btw)...is this possible? or do I
have to have ethernet?

   LC475-macos
        |
        |
        |<-----Serial cable
        |
        |
   LCIII-NetBSD
        |
        |
        |
      Modem