Yes it's possible, I haven't done it myself, but there are a few videos on youtube showing it. This one came up when I googled it:
Read the description on that video, it has pretty much all the info you need. You can get the latest wii-network branch of dolphin here: https://dolphin-emu.org/download/list/wii-network/
EDIT: is there no way to just link to a youtube video? Will it always just show as embedded on gbatemp?
it worked for me with mkwii, brawl and pokemon battle revolutionDoes it only work for MK Wii? I get connection errors with other games that use Nintendo WFC