# smol
[](
https://github.com/stjepang/smol/actions)
[](
https://github.com/stjepang/smol)
[](
https://crates.io/crates/smol)
[](
https://docs.rs/smol)
[](
https://discord.gg/x6m5Vvt)
A small and fast async runtime.
## Examples
Connect to an HTTP website, make a GET request, and pipe the response to the standard output:
```rust
use async_net::TcpStream;
use smol::{io, prelude::*, Unblock};
fn main() -> io::Result<()> {
smol::run(async {
let mut stream = TcpStream::connect("example.com:80").await?;
let req = b"GET / HTTP/1.1\r\nHost: example.com\r\nConnection: close\r\n\r\n";
stream.write_all(req).await?;
let mut stdout = Unblock::new(std::io::stdout());
io::copy(&stream, &mut stdout).await?;
Ok(())
})
}
```
This example uses [`async-net`] for networking, but you can also use the primitive `Async`
type. See the [full code][get-request].
Look inside the [examples] directory for more.
[`async-net`]: https://docs.rs/async-net
[examples]: https://github.com/stjepang/smol/tree/master/examples
[get-request]: https://github.com/stjepang/smol/blob/master/examples/get-request.rs
## Compatibility
All async libraries work with smol out of the box.
The only exception is [tokio], which is traditionally incompatible with [futures] and crashes
when called from other executors. Fortunately, there are ways around it.
Enable the `tokio02` feature flag and `smol::run()` will create a minimal
tokio runtime for its libraries:
```toml
[dependencies]
smol = { version = "0.3", features = ["tokio02"] }
```
[tokio]: https://docs.rs/tokio
[futures]: https://docs.rs/futures
## TLS certificate
Some code examples are using TLS for authentication. The repository
contains a self-signed certificate usable for testing, but it should **not**
be used for real-world scenarios. Browsers and tools like curl will
show this certificate as insecure.
In browsers, accept the security prompt or use `curl -k` on the
command line to bypass security warnings.
The certificate file was generated using
[minica](https://github.com/jsha/minica) and
[openssl](https://www.openssl.org/):
```
minica --domains localhost -ip-addresses 127.0.0.1 -ca-cert certificate.pem
openssl pkcs12 -export -out identity.pfx -inkey localhost/key.pem -in localhost/cert.pem
```
Another useful tool for making certificates is [mkcert].
[mkcert]: https://github.com/FiloSottile/mkcert
## License
Licensed under either of
* Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
* MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
at your option.
#### Contribution
Unless you explicitly state otherwise, any contribution intentionally submitted
for inclusion in the work by you, as defined in the Apache-2.0 license, shall be
dual licensed as above, without any additional terms or conditions.