I can’t play online for some reason? Help me please!

My dodo code is LVGNF

"I have all fruits! I can give them for 500 bells each :) "
posted on nookfriends.com

New to this all would like different fruit have apples and oranges need codes please

Hi I want to visit other islands

I need to sell peaches and turnips. Also Annalisa is leaving my island

Getting bored playing by myself this is my friend code 6828-7886-5664

I want to visit an island. I'm new. Send me a dodo code.

Hi I want to make new friends!!

gates are open if you added me earlier!!! be friendly, bring clothes and/fruit... will give golden nugget for 10 pears or peaches

if you want golden watering can come to my island

So I am totally new to online play, can someone tell me does the person you are visiting have to be actively playing at the time you visit their island or can a person just visit whenever? Is it like the "couch play" type multiplayer with a leader/follower thing?