I have a CD32 Networking kit, which is a serial cable, connecting to the CD32 Aux port at one end, and the Amiga serial port at the other.
It comes with a bootable CD for the CD32 and a disk for the other Amiga (although there are also DMS disk images on the CD if you get a corrupted floppy, which I guess happens after having this for about 15 years).
It allows file transfer from the CD32 to the Amiga, but not much else. Also, it is very slow (there are a range of serial port speeds, but the faster you choose, the more likely it is for the link to drop, meaning a reboot at both ends). The last time I used it was to take the CD32 ROM image to use in UAE.
From the Amiga end, you can access the CD32 drives (CD, RAM, floppy if you have one).
