> 何してんの?

The translated meaning is "what are you doing?", but I am having difficulty
understanding how the て form of する is referring to the present tense (I would
have expected している here).

Also, I am not comfortable with the "ん", although I have seen it appear
before.
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2018-08-05T16:06:54.287
60697
2022-04-28T01:45:51.477
2018-08-05T16:08:12.813
30417
question
syntax colloquial-language particle-の contractions
Can somebody give me a grammatical insight into the following very short sentence?