An incomplete, untested Swifty socket library
Socket6 and sockaddr_in6 are simple wrappers for a subset the socket API - they don't add functionality, but only hide the ghastliness of persuading Swift's strict type system to talk to an 80's-style C API.
StreamSocket and DatagramSocket are higher-level classes for doing asynchronous reading and writing on TCP and UDP sockets respectively.
SwiftySockets is IPv6 only. That isn't quite as dumb as it seems, as your OS will bridge to and from IPv4 networks automagically.
It also requires Swift 3 / XCode 8, although you could probably port it back to Swift 2 without much trouble.
At this point, just read the code, it's fairly self-explanatory.