It's really tempting here to call the speaker Neruda himself, because of the reference to Maru Mori (see "Shout-Outs" for more on her), his actual friend who knitted the beloved socks. However, that's really the only clue linking the speaker to Neruda, and since we can't be sure that he was Maru Mori's only friend (she probably knitted socks for other people too, or maybe the whole thing was invented), we can't call the speaker Neruda with any degree of certainty.
What we do know is that the speaker was someone lucky enough to get a semi-famous person to knit them some socks, so that tells us that the speaker is probably in the intellectual or artistic circles of Chile (again, check out "Shout-Outs" for the skinny on Maru Mori). More than that, though, we can also infer that the speaker is someone who feels strongly about those handmade socks and wants to exalt them in a poem, while always reminding the reader of their real-life usefulness.
In this kind of praise, then, we can understand the speaker as someone who really appreciates craft, human creation, charity, and usefulness. In other words, this is not some high-falutin' fellow (we can just assume the speaker's a "he") who rushes off to the mountain top to praise the sun for rising. No, he's got his eye on the lived materials of daily life. Even there, or especially there, he finds things to appreciate. As readers, we're invited to explore that same kind of gratitude right along with him, which we think is just super-refreshing. Rather than grumbling about your latest iDevice because it doesn't edit 3-D movies as quickly as you'd like, try to appreciate the simpler things in life, things that come from the heart—like our speaker's socks!