LAN has nothing to do with anything in tamagotchi... Tamagotchi has no access to the internet. None of them do.
It has to be IRDA Transfer, and I don't reccomend getting a dongle for that because they barely work and they're expensive. An old IRDA compatible phone is pretty much GUARANTEED to work and costs about the same.
These cheap IRDA dongles you can find on ebay won't work because they're just for remotes.