Check out this sentence:
おい！ きいてん の ？！
Hey! Are you listening?!
Literally: "hey! + are listening + の?!"
This sentence is nice and rude... or rather, angry-sounding. So, don't use it when having tea with the emperor... or just about ever, to be honest.
You'll hear this kind of language, though, particularly in TV shows.
おい! is a phrase meaning something like "Hey!" It's pretty versatile and is used when getting someone's attention. It's not appropriate for most formal situations, though.
Look at this progression of sentences, which starts with a somewhat casual question and becomes more and more casual:
(Note: I'm not writing the kana breakdowns, but remember that 聞いて is pronounced きいて.)
↓ ↓ ↓
↓ ↓ ↓
It took me several years to figure out that ～ているの？is ～てんの？
Why didn't anyone teach me?!
Anyway, now you know.
なに やってん の？
What're you doin'?
Literally: "what + are doing + の?"
Literally: "not especially / not particularly."