Telemachus and Eumeaus the swineherd do not reunite until the first lines of Book 16. In that reunion the metaphor is one of a father welcoming a son returned from a foreign war. Since Eumeaus is not Telemachus' father, but Odysseus, whom Telemachus does not yet know, is his father, this simile creates irony. The description of the scene is exactly how, if Telemachus had been old enough to go to Troy, and if Odysseus had waited at home for him, the reunion between the two of them would have been. Since this happens with Telemachus's own bedraggled and unrecognized father sitting and watching merely as a "guest-friend", it is both ironic and heartbreaking:
Just as a father in loving benevolence welcomes a dear son
who in the tenth year comes back home from a faraway country,
his sole child and his darling, for whom much grief he has suffered,
so now Telemachos, godlike in beauty, the excellent swineherd
kissed and embraced all over, as one whom had fled from destruction. (290)
The Trojan War lasted ten years, so if Odysseus had been able to get back home immediately this simile would have been exactly how the father and son would have embraced. Since the gods delayed his return another ten years Telemachus has grown into a man and Odysseus has missed his entire childhood. Eumeaus has stood in as a father, and Odysseus must be aggrieved to see what he has missed.
Test Source: Homer, The Odysssey. Trans. by Rodney Merrill. Ann Arbor: U of Michigan Press, 2006.