# localhost(_:) Returns a loopback endpoint (`127.0.0.1:port`) for the given port. ``` static func localhost(_ port: Int) -> HostPort ``` ## Parameters `port` TCP port on 127.0.0.1. ## Return Value A fresh `HostPort` with `host == "127.0.0.1"`. ## Discussion Convenience factory for the most common shape of `HostPort` inside swift-tor: Tor’s SOCKS and control endpoints both live on the loopback interface, and the overwhelming majority of callers never need a non-loopback host. Using this factory makes it impossible to typo `"127.0.0.1"` at call sites and keeps intent explicit. > Note: This factory always returns an **IPv4** loopback. If you > need IPv6 loopback (`::1`), construct the value explicitly via > ``doc://Tor/documentation/Tor/HostPort/init(host:port:)``. The two loopback families are distinct at > the kernel socket layer and will not unify on `connect(2)`. > Important: The string literal `"localhost"` is deliberately **not** > used here to avoid an unnecessary DNS lookup on Apple platforms.