While dishwasher is running the smell of rotten eggs coming from the vent . When not running it still smell like rotten eggs

If dishes are not rinsed off properly before going in the dishwasher, left over food will find lower places to settle and rot, usually in places you can't see. There are products on the market now, some better then others, that allow you to give your dishwasher a good cleaning.

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Are you on a well or city water?

By "vent" do you mean a counter top air gap? (see image)
Have you sponged out the sump and scrubbed it down with bleach? Let me know, Tom