I have a LAN port upstairs in the kitchen. I have scoured the house for a second port. No luck. I cannot find an external LAN box outside anywhere. I live downstairs and have very poor wifi. Is there an easy way to determine if there is in fact a second port downstairs? I would like to have the router downstairs, as my father doesn’t use the internet for much and is uninterested in the fact that the connection is weak everywhere else in the house.

How do I determine if there is a second port? I would like to avoid drilling holes in walls to run cable.