I spent some time on the pre-release for Turbo/64 BBS adding external door capabilities. It was challenging given the memory constraints on the Commodore 64 -- even with 16MB REU -- and created a release along with a rudimentary dev kit so people can CREATE doors as well.
https://github.com/robbiew/turbo64
From the README:
Doors are external programs the BBS loads and runs during a call - games, utilities, info screens. A door is a separate Oscar64 .prg built to load at $9700; the BBS hands it a small SDK (print, read input, display a file, caller info) and reloads itself when the door exits. They're configured in CONFIGURE and run from the ! (DOOR PROGRAMS) entry on the main menu, or automatically at login.
The release disk bundles an example door, FORTUNE (FORTUNE.PRG), so you can try the system without writing any code. submitted by /u/robbiew [link] [comments]