How did darth vader know it was skywalker on hoth?

I was watching empire strikes back n noticed that he said skywalker is
on hoth, but luke n vader have never met, have they? Not in new hope
too. Like how does he even know there is a skywalker has someone
notified him plus how did he know he was with the rebels. So how did
he know. Thanks, yes I'm a fanatic.