Event

Async TCP sockets and event-loop primitives for Swift, backed by a vendored build of libevent.

Overview

Event is the idiomatic Swift face of this package. It wraps libevent 2.1.12’s event-dispatch machinery behind Swift 6.1 structured concurrency so you can write async/await code against non-blocking TCP sockets on macOS 13+, iOS 16+, tvOS 16+, watchOS 9+, visionOS 1+, and Linux (Ubuntu 22.04+). The package selects the most efficient I/O multiplexer available at runtime — kqueue on Apple platforms, epoll on Linux — and exposes it through a small, typed surface with no raw OpaquePointer leakage.

Direct-use capabilities shipping today:

Event-loop control — create a loop, drive it per-operation or long-lived, inspect the backend. See EventLoop.
Async TCP client — async throws connect / read / write / close. See Socket.
Async TCP server — bind / listen / accept and an AsyncThrowingStream of incoming connections. See ServerSocket.
Address construction — numeric IPv4 / IPv6 / wildcard factories over sockaddr_storage. See SocketAddress.

import Event

let loop = EventLoop()
print(loop.backendMethod)
// kqueue   (on macOS / iOS / tvOS / watchOS / visionOS)
// epoll    (on Linux)

Foundation Runtime for Swift Network Stacks

Beyond its direct API, this package ships the raw libevent C binding product that other Swift packages link against when they need libevent primitives this Swift API hasn’t wrapped yet (timer events via evtimer_*, signal events via evsignal_*, custom bufferevents, DNS resolution via evdns_*). The concrete example is swift-tor, whose libtor target depends on libevent (from this package) alongside libcrypto / libssl (from swift-openssl) to build a Swift-native Tor daemon. See Choosing Between Event and libevent for product-selection guidance.

API positioning: Event is a thin, libevent-direct, async/await wrapper. It is not a replacement for SwiftNIO — if you need NIO’s channel pipelines, back-pressure protocol handlers, or HTTP/2 / WebSocket / TLS off-the-shelf, reach for NIO. Reach for Event when you want minimal abstraction over the platform multiplexer, a small dependency surface, or tight interop with C code that already speaks libevent.

Topics

Essentials