# Tokio A runtime for writing reliable, asynchronous, and slim applications with the Rust programming language. It is: * **Fast**: Tokio's zero-cost abstractions give you bare-metal performance. * **Reliable**: Tokio leverages Rust's ownership, type system, and concurrency model to reduce bugs and ensure thread safety. * **Scalable**: Tokio has a minimal footprint, and handles backpressure and cancellation naturally. [![Crates.io][crates-badge]][crates-url] [![MIT licensed][mit-badge]][mit-url] [![Build Status][actions-badge]][actions-url] [![Discord chat][discord-badge]][discord-url] [crates-badge]: https://img.shields.io/crates/v/tokio.svg [crates-url]: https://crates.io/crates/tokio [mit-badge]: https://img.shields.io/badge/license-MIT-blue.svg [mit-url]: https://github.com/tokio-rs/tokio/blob/master/LICENSE [actions-badge]: https://github.com/tokio-rs/tokio/workflows/CI/badge.svg [actions-url]: https://github.com/tokio-rs/tokio/actions?query=workflow%3ACI+branch%3Amaster [discord-badge]: https://img.shields.io/discord/500028886025895936.svg?logo=discord&style=flat-square [discord-url]: https://discord.gg/tokio [Website](https://tokio.rs) | [Guides](https://tokio.rs/tokio/tutorial) | [API Docs](https://docs.rs/tokio/latest/tokio) | [Chat](https://discord.gg/tokio) ## Overview Tokio is an event-driven, non-blocking I/O platform for writing asynchronous applications with the Rust programming language. At a high level, it provides a few major components: * A multithreaded, work-stealing based task [scheduler]. * A reactor backed by the operating system's event queue (epoll, kqueue, IOCP, etc...). * Asynchronous [TCP and UDP][net] sockets. These components provide the runtime components necessary for building an asynchronous application. [net]: https://docs.rs/tokio/latest/tokio/net/index.html [scheduler]: https://docs.rs/tokio/latest/tokio/runtime/index.html ## Example A basic TCP echo server with Tokio: ```rust,no_run use tokio::net::TcpListener; use tokio::io::{AsyncReadExt, AsyncWriteExt}; #[tokio::main] async fn main() -> Result<(), Box> { let mut listener = TcpListener::bind("127.0.0.1:8080").await?; loop { let (mut socket, _) = listener.accept().await?; tokio::spawn(async move { let mut buf = [0; 1024]; // In a loop, read data from the socket and write the data back. loop { let n = match socket.read(&mut buf).await { // socket closed Ok(n) if n == 0 => return, Ok(n) => n, Err(e) => { eprintln!("failed to read from socket; err = {:?}", e); return; } }; // Write the data back if let Err(e) = socket.write_all(&buf[0..n]).await { eprintln!("failed to write to socket; err = {:?}", e); return; } } }); } } ``` More examples can be found [here][examples]. For a larger "real world" example, see the [mini-redis] repository. [examples]: https://github.com/tokio-rs/tokio/tree/master/examples [mini-redis]: https://github.com/tokio-rs/mini-redis/ To see a list of the available features flags that can be enabled, check our [docs][feature-flag-docs]. ## Getting Help First, see if the answer to your question can be found in the [Guides] or the [API documentation]. If the answer is not there, there is an active community in the [Tokio Discord server][chat]. We would be happy to try to answer your question. You can also ask your question on [the discussions page][discussions]. [Guides]: https://tokio.rs/tokio/tutorial [API documentation]: https://docs.rs/tokio/latest/tokio [chat]: https://discord.gg/tokio [discussions]: https://github.com/tokio-rs/tokio/discussions [feature-flag-docs]: https://docs.rs/tokio/#feature-flags ## Contributing :balloon: Thanks for your help improving the project! We are so happy to have you! We have a [contributing guide][guide] to help you get involved in the Tokio project. [guide]: https://github.com/tokio-rs/tokio/blob/master/CONTRIBUTING.md ## Related Projects In addition to the crates in this repository, the Tokio project also maintains several other libraries, including: * [`hyper`]: A fast and correct HTTP/1.1 and HTTP/2 implementation for Rust. * [`tonic`]: A gRPC over HTTP/2 implementation focused on high performance, interoperability, and flexibility. * [`warp`]: A super-easy, composable, web server framework for warp speeds. * [`tower`]: A library of modular and reusable components for building robust networking clients and servers. * [`tracing`]: A framework for application-level tracing and async-aware diagnostics. * [`rdbc`]: A Rust database connectivity library for MySQL, Postgres and SQLite. * [`mio`]: A low-level, cross-platform abstraction over OS I/O APIs that powers `tokio`. * [`bytes`]: Utilities for working with bytes, including efficient byte buffers. * [`loom`]: A testing tool for concurrent Rust code [`warp`]: https://github.com/seanmonstar/warp [`hyper`]: https://github.com/hyperium/hyper [`tonic`]: https://github.com/hyperium/tonic [`tower`]: https://github.com/tower-rs/tower [`loom`]: https://github.com/tokio-rs/loom [`rdbc`]: https://github.com/tokio-rs/rdbc [`tracing`]: https://github.com/tokio-rs/tracing [`mio`]: https://github.com/tokio-rs/mio [`bytes`]: https://github.com/tokio-rs/bytes ## Supported Rust Versions Tokio is built against the latest stable release. The minimum supported version is 1.45. The current Tokio version is not guaranteed to build on Rust versions earlier than the minimum supported version. ## License This project is licensed under the [MIT license]. [MIT license]: https://github.com/tokio-rs/tokio/blob/master/LICENSE ### Contribution Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in Tokio by you, shall be licensed as MIT, without any additional terms or conditions.