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.

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 sockets.

These components provide the runtime components necessary for building an asynchronous application.

Example

To get started, add the following to Cargo.toml.

toml tokio = { version = "0.2", features = ["full"] }

Tokio requires components to be explicitly enabled using feature flags. As a shorthand, the full feature enables all components.

A basic TCP echo server with Tokio:

```rust,no_run use tokio::net::TcpListener; use tokio::prelude::*;

[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.

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. We would be happy to try to answer your question. Last, if that doesn't work, try opening an [issue] with the question.

Contributing

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

Related Projects

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

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

Supported Rust Versions

Tokio is built against the latest stable, nightly, and beta Rust releases. The minimum version supported is the stable release from three months before the current 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 not guaranteed to build on Rust versions earlier than the minimum supported version.

License

This project is licensed under the MIT 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.