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https://github.com/tokio-rs/mio

Metal I/O library for Rust.
https://github.com/tokio-rs/mio

asynchronous networking non-blocking rust

Last synced: 3 days ago
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Metal I/O library for Rust.

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README 

        
# Mio – Metal I/O



Mio is a fast, low-level I/O library for Rust focusing on non-blocking APIs and

event notification for building high performance I/O apps with as little

overhead as possible over the OS abstractions.



[![Crates.io][crates-badge]][crates-url]

[![MIT licensed][mit-badge]][mit-url]

[![Build Status][actions-badge]][actions-url]

[![Build Status][cirrus-badge]][cirrus-url]



[crates-badge]: https://img.shields.io/crates/v/mio.svg

[crates-url]: https://crates.io/crates/mio

[mit-badge]: https://img.shields.io/badge/license-MIT-blue.svg

[mit-url]: LICENSE

[actions-badge]: https://github.com/tokio-rs/mio/workflows/CI/badge.svg

[actions-url]: https://github.com/tokio-rs/mio/actions?query=workflow%3ACI+branch%3Amaster

[cirrus-badge]: https://api.cirrus-ci.com/github/tokio-rs/mio.svg

[cirrus-url]: https://cirrus-ci.com/github/tokio-rs/mio



**API documentation**



* [v1](https://docs.rs/mio/^1)

* [v0.8](https://docs.rs/mio/^0.8)



This is a low level library, if you are looking for something easier to get

started with, see [Tokio](https://tokio.rs).



## Usage



To use `mio`, first add this to your `Cargo.toml`:



```toml

[dependencies]

mio = "1"

```



Next we can start using Mio. The following is quick introduction using

`TcpListener` and `TcpStream`. Note that `features = ["os-poll", "net"]` must be

specified for this example.



```rust

use std::error::Error;



use mio::net::{TcpListener, TcpStream};

use mio::{Events, Interest, Poll, Token};



// Some tokens to allow us to identify which event is for which socket.

const SERVER: Token = Token(0);

const CLIENT: Token = Token(1);



fn main() -> Result<(), Box> {

    // Create a poll instance.

    let mut poll = Poll::new()?;

    // Create storage for events.

    let mut events = Events::with_capacity(128);



    // Setup the server socket.

    let addr = "127.0.0.1:13265".parse()?;

    let mut server = TcpListener::bind(addr)?;

    // Start listening for incoming connections.

    poll.registry()

        .register(&mut server, SERVER, Interest::READABLE)?;



    // Setup the client socket.

    let mut client = TcpStream::connect(addr)?;

    // Register the socket.

    poll.registry()

        .register(&mut client, CLIENT, Interest::READABLE | Interest::WRITABLE)?;



    // Start an event loop.

    loop {

        // Poll Mio for events, blocking until we get an event.

        poll.poll(&mut events, None)?;



        // Process each event.

        for event in events.iter() {

            // We can use the token we previously provided to `register` to

            // determine for which socket the event is.

            match event.token() {

                SERVER => {

                    // If this is an event for the server, it means a connection

                    // is ready to be accepted.

                    //

                    // Accept the connection and drop it immediately. This will

                    // close the socket and notify the client of the EOF.

                    let connection = server.accept();

                    drop(connection);

                }

                CLIENT => {

                    if event.is_writable() {

                        // We can (likely) write to the socket without blocking.

                    }



                    if event.is_readable() {

                        // We can (likely) read from the socket without blocking.

                    }



                    // Since the server just shuts down the connection, let's

                    // just exit from our event loop.

                    return Ok(());

                }

                // We don't expect any events with tokens other than those we provided.

                _ => unreachable!(),

            }

        }

    }

}

```



## Features



* Non-blocking TCP, UDP, UDS

* I/O event queue backed by epoll, kqueue, and IOCP

* Zero allocations at runtime

* Platform specific extensions



## Non-goals



The following are specifically omitted from Mio and are left to the user

or higher-level libraries.



* File operations

* Thread pools / multi-threaded event loop

* Timers



## Platforms



Currently supported platforms:



* Android (API level 21)

* DragonFly BSD

* FreeBSD

* Linux

* NetBSD

* OpenBSD

* Windows

* iOS

* macOS



Mio can handle interfacing with each of the event systems of the aforementioned

platforms. The details of their implementation are further discussed in the

`Poll` type of the API documentation (see above).



Mio generally supports the same versions of the above mentioned platforms as

Rust the language (rustc) does, unless otherwise noted.



The Windows implementation for polling sockets is using the [wepoll] strategy.

This uses the Windows AFD system to access socket readiness events.



[wepoll]: https://github.com/piscisaureus/wepoll



### Unsupported



* Wine, see [issue #1444]



[issue #1444]: https://github.com/tokio-rs/mio/issues/1444



## MSRV Policy



The MSRV (Minimum Supported Rust Version) is fixed for a given minor (1.x)

version. However it can be increased when bumping minor versions, i.e. going

from 1.0 to 1.1 allows us to increase the MSRV. Users unable to increase their

Rust version can use an older minor version instead. Below is a list of Mio versions

and their MSRV:



 * v0.8: Rust 1.46.

 * v1.0: Rust 1.70.



Note however that Mio also has dependencies, which might have different MSRV

policies. We try to stick to the above policy when updating dependencies, but

this is not always possible.



## Unsupported flags



Mio uses different implementations to support the same functionality depending

on the platform. Mio generally uses the "best" implementation possible, where

"best" usually means most efficient for Mio's use case. However this means that

the implementation is often specific to a limited number of platforms, meaning

we often have multiple implementations for the same functionality. In some cases

it might be required to not use the "best" implementation, but another

implementation Mio supports (on other platforms). **Mio does not officially

support secondary implementations on platforms**, however we do have various cfg

flags to force another implementation for these situations.



Current flags:

 * `mio_unsupported_force_poll_poll`, uses an implementation based on `poll(2)`

   for `mio::Poll`.

 * `mio_unsupported_force_waker_pipe`, uses an implementation based on `pipe(2)`

   for `mio::Waker`.



**Again, Mio does not officially supports this**. Furthermore these flags may

disappear in the future.



## Community



A group of Mio users hang out on [Discord], this can be a good place to go for

questions. It's also possible to open a [new issue on GitHub] to ask questions,

report bugs or suggest new features.



[Discord]: https://discord.gg/tokio

[new issue on GitHub]: https://github.com/tokio-rs/mio/issues/new



## Contributing



Interested in getting involved? We would love to help you! For simple

bug fixes, just submit a PR with the fix and we can discuss the fix

directly in the PR. If the fix is more complex, start with an issue.



If you want to propose an API change, create an issue to start a

discussion with the community. Also, feel free to talk with us in Discord.



Finally, be kind. We support the [Rust Code of Conduct](https://www.rust-lang.org/policies/code-of-conduct).