Just wear a nice suit. Preferably black. No one is policing the attire. You'll just stand out by not wearing a tux or black suit. But you'll have no problem getting in. Have fun!
No, you don't have to wear a tux. If you don't own one, for most people the extra cost of renting one is pretty silly. And don't worry about it either. No one will really care.
If we're not having fun, then why are we doing it?
These are DISCUSSION boards, not mutual admiration boards. Discussion only occurs when we are willing to hear what others are thinking, regardless of whether it is alignment to our own thoughts.
Went last year and was very stressed about being able to get in. I wore a black suit and there was no issue being admitted. A gentleman a few rows behind me was wearing khakis and a polo shirt.