how many times is it acceptable to knock/ring someones doorbell?

I feel kinda bad now because I just freaked out on some guy at the door.

First, I never answer the door if my husband is not home. Second, my toddler is screaming and crying at the top of his lungs, throwing a huge tantrum that I'm sure he could hear and I'm running around trying to make him lunch which I'm sure he could see through our glass door. But he kept ringing on knocking on the door. Ughhhhh. Am I over reacting for being super pissed about this?