swift-nio
Event-driven network application framework for high performance protocol servers & clients, non-blocking.
SwiftNIO is a networking library from Apple for Swift that handles thousands of simultaneous server connections efficiently using an event-driven, non-blocking model, no separate thread needed per connection.
SwiftNIO is a networking library built by Apple that helps developers create fast servers and clients in the Swift programming language. It is designed around an event-driven model, meaning it handles many network connections at the same time without waiting for each one to finish before moving to the next. This approach allows servers to process thousands of simultaneous requests efficiently without needing a separate thread for each connection.
The library is organized into several modules. The core module provides the foundational types that other modules and third-party libraries build on top of. There are separate modules for handling HTTP/1, HTTP/2, WebSocket connections, and TLS (the encryption layer used by HTTPS). Developers who want to support Apple-specific platforms like iOS, tvOS, and watchOS can use an additional package called swift-nio-transport-services that integrates with Apple's native networking APIs.
A notable feature of the design is that SwiftNIO operates without blocking the program. Traditional network code often pauses the program to wait for data to arrive over the network. SwiftNIO avoids this by notifying the program only when data is ready, which keeps the system free to handle other work in the meantime. This is similar to how some popular web server toolkits work in other programming languages.
The project is split across multiple repositories, each covering a different protocol or feature area. The main repository here covers the core abstractions plus HTTP/1 and WebSocket support. Companion repositories provide TLS encryption, HTTP/2, SSH support, and other additions. The project has graduated through Apple's Swift Server Work Group, indicating it is considered stable and production-ready.
SwiftNIO supports macOS, Linux, and iOS, and it works with recent versions of Swift. The README is longer than what was shown.
Where it fits
- Build a high-performance HTTP or WebSocket server in Swift that handles thousands of concurrent connections.
- Create a custom network protocol handler in Swift that runs on macOS or Linux without blocking threads.
- Add non-blocking TLS or HTTP/2 support to a Swift server using companion SwiftNIO packages.