φθέγγεο, μὴ δ᾽ ἀκέων ἐπ᾽ ἒμ᾽ ἔρχεο
See “The Poetics of Ambush” on the sensory aspects of the night. In 10.67, Agamemnon told Menelaos to call out (φθέγγεο as here) wherever he went, which in the dark would serve both to wake up his comrades and let them know that he was their fellow Achaean and not [TEST] an enemy. So here Nestor tells his visitor not to sneak up on him in the dark, but to call out to let him know who he is and why he is there. See also Iliad 10.139 and 24.170.