From a .txt file that I made a while ago. IMPORTANT NOTE.txt

For adonis to be working, you MUST set th09.exe, th09e.exe, adonis.exe AND adonise.exe in
Windows 98 / Millenium compatibility mode AND also disable desktop composition.

If it's still not working it might be a port problem, you should try to disable your firewall
if it still not working, plug your internet connexion directly on your computer instead of hiding
behind a router (or try to set your computer in the DMZ zone one your router, that's the equivalent)
if this solves the problem, you will need to do a port foward (portforward.com can be a good start
for help)

It's also recommanded to set it in windowed mode. If you want to
run it fullscreen, alt+tabbing will crash the game.