MongoDB LOG Connection Port

[Riccardo Amadio]

Hi 
I search on log of mongodb on path '/var/log/mongodb/mongodb.log'.
I found this connection :

2017-06-20T23:58:15.930+0200 I NETWORK  [conn14] received client metadata from 127.0.0.1:58007 conn14

Why the connection give me the port?? 
I don't change the default port of connection , why it isn't 27017 ?

Thanks