tokio

# 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.

Make sure you enable the full features of the tokio crate on Cargo.toml:

```toml
[dependencies]
tokio = { version = "1.54.1", features = ["full"] }
```
Then, on your main.rs:

```rust,no_run
use tokio::net::TcpListener;
use tokio::io::{AsyncReadExt, AsyncWriteExt};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let 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(0) => return,
                    Ok(n) => n,
                    Err(e) => {
                        eprintln!("failed to read from socket; err = {:?}", e);
                        return;
                    }
                };

                // Write the data back