olemus
(a) otseselt helisid tähele panema
= to pay attention to or expect for a sound or speech

(b) kontekstist sõltuva metafoorina mingit olekut jälgima
= metaphorically, to check a status of a context-dependent object

näide
porti kuulama, st ooteolekus viibides porti jälgima,
ühenduskatsetele reageerimiseks
= to listen a port: in a waiting mode checking the activity on a port, to respond to the connection attempts
https://stackoverflow.com/questions/7470296/what-exactly-is-port-listening