Atari++, an Atari 400, 800, 600 XL, 800 XL, 1200 XL, 65 XE, 130 XE and 5200 emulator has been updated to version 1.39 Here is what is new in this version:
  • Added a serial transport interface allowing portable serial communications from Linux and Win32. This allows this release to enable the 850 Interface box and AtariSIO implementation for Win32.
You can get it from here.