I actually did have to write an HTTP library on sockets once. It wasn’t trivial (took a month to productionize), but it was core to our business. We were writing developer tools (Parse) and our file upload library had major problems on the latest iPhone due to an OS bug (if a kernel buffer filled before the modem could upload it, the file transfer would fail).

We became the third company I know about to ever solve this problem, but I had built what my colleague called “the hardest to use HTTP library ever”. I was happy to move back to AFNetworking once we could do so without a regression in performance or hitting that bug.