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A runtime for writing reliable asynchronous applications with Rust. Provides I/O, networking, scheduling, timers, …


A runtime for writing reliable, asynchronous, and slim applications withthe Rust programming language. It is:

  • Fast: Tokio’s zero-cost abstractions give you bare-metalperformance.

  • Reliable: Tokio leverages Rust’s ownership, type system, andconcurrency model to reduce bugs and ensure thread safety.

  • Scalable: Tokio has a minimal footprint, and handles backpressureand cancellation naturally.

Crates.ioMIT licensedBuild StatusDiscord chat

Website |Guides |API Docs |Chat


Tokio is an event-driven, non-blocking I/O platform for writingasynchronous applications with the Rust programming language. At a highlevel, 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 sockets.

These components provide the runtime components necessary for buildingan asynchronous application.


A basic TCP echo server with Tokio:

“`rust,no_runuse tokio::net::TcpListener;use tokio::prelude::*;


async fn main() -> Result { let mut listener = TcpListener::bind(“”).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 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. Note that the master branchis currently being updated to use async / await. The examples arenot fully ported. Examples for stable Tokio can be foundhere.

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 inthe Tokio Discord server. We would be happy to try to answer yourquestion. Last, if that doesn’t work, try opening an [issue] with the question.


:balloon: Thanks for your help improving the project! We are so happy to haveyou! We have a contributing guide to help you get involved in the Tokioproject.

Related Projects

In addition to the crates in this repository, the Tokio project also maintainsseveral other libraries, including:

  • [tracing] (formerly tokio-trace): A framework for application-leveltracing and async-aware diagnostics.

  • [mio]: A low-level, cross-platform abstraction over OS I/O APIs that powerstokio.

  • [bytes]: Utilities for working with bytes, including efficient byte buffers.

Supported Rust Versions

Tokio is built against the latest stable, nightly, and beta Rust releases. Theminimum version supported is the stable release from three months before thecurrent stable release version. For example, if the latest stable Rust is 1.29,the minimum version supported is 1.26. The current Tokio version is notguaranteed to build on Rust versions earlier than the minimum supported version.


This project is licensed under the MIT license.


Unless you explicitly state otherwise, any contribution intentionally submittedfor inclusion in Tokio by you, shall be licensed as MIT, without any additionalterms or conditions.

To restore the repository download the bundle


and run:

 git clone tokio-rs-tokio_-_2019-11-29_07-12-27.bundle 

Uploader: tokio-rs
Upload date: 2019-11-29