Well, I finally figured it out, and it wasn’t that complex after all.
In Windows Vice 3.1, make these settings in RS-232 Settings
ACIA Settings -> Off (Do not enable ACIA)
Userport Settings -> Device 1 -> 2400 Baud
RS232 Settings -> Device 1 -> 192.168.0.xx:25232
The xx is your local machine IP. (In windows, check Ethernet Settings -> Hardware Properties -> IPv4 Address)
Then get tcpser going with these settings in command prompt:
tcpser -v 25232 -p 6400 -s 2400 -l 4
Load CCGMS, use User Port 300-2400 and 2400 baud settings.
As with all versions of vice, file transfers do not work. If you want to upload and download programs, get a real c64. 🙂 Or use CGTerm.