How do I make an HTTP request from Rust?

How can I make an HTTP request from Rust? I can't seem to find anything in the core library.

I don't need to parse the output, just make a request and check the HTTP response code.

Bonus marks if someone can show me how to URL encode the query parameters on my URL!

Update: This answer refers to fairly ancient history. For the current best practices, please look at Isaac Aggrey's answer instead.

I've been working on rust-http, which has become the de facto HTTP library for Rust (Servo uses it); it's far from complete and very poorly documented at present. Here's an example of making a request and doing something with the status code:

extern mod http;
use http::client::RequestWriter;
use http::method::Get;
use http::status;
use std::os;

fn main() {
    let request = RequestWriter::new(Get, FromStr::from_str(os::args()[1]).unwrap());
    let response = match request.read_response() {
        Ok(response) => response,
        Err(_request) => unreachable!(), // Uncaught condition will have failed first
    };
    if response.status == status::Ok {
        println!("Oh goodie, I got me a 200 OK response!");
    } else {
        println!("That URL ain't returning 200 OK, it returned {} instead", response.status);
    }
}

Run this code with a URL as the sole command-line argument and it'll check the status code! (HTTP only; no HTTPS.)

Compare with src/examples/client/client.rs for an example that does a little more.

rust-http is tracking the master branch of rust. ~~At present it'll work in the just-released Rust 0.8, but there are likely to be breaking changes soon.~~ Actually, no version of rust-http works on Rust 0.8—there was a breaking change which can't be worked around in privacy rules just before the release, leaving something that rust-http depends on in extra::url inaccessible. This has since been fixed, but it leaves rust-http incompatible with Rust 0.8.

As for the query string encoding matter, at present that should be done with extra::url::Query (a typedef for ~[(~str, ~str)]). Appropriate functions for conversions:

extra::url::query_to_str
extra::url::query_from_str (sorry, can't use this just at present as it's private. PR to make it public about to come. In the mean time, this link actually shouldn't work, it's only available because of https://github.com/mozilla/rust/issues/7476.)

The easiest way to do HTTP in Rust is reqwest. It is a wrapper to make Hyper easier to use.

Hyper is a popular HTTP library for Rust and utilizes two libraries: Tokio's event loop to make non-blocking requests and futures-rs for futures/promises. A Hyper-based example is below and is largely inspired by an example in its documentation.

// Rust 1.19, Hyper 0.11, tokio-core 0.1, futures 0.1

extern crate futures;
extern crate hyper;
extern crate tokio_core;

use futures::{Future};
use hyper::{Client, Uri};
use tokio_core::reactor::Core;

fn main() {
    // Core is the Tokio event loop used for making a non-blocking request
    let mut core = Core::new().unwrap();

    let client = Client::new(&core.handle());

    let url : Uri = "http://httpbin.org/response-headers?foo=bar".parse().unwrap();
    assert_eq!(url.query(), Some("foo=bar"));

    let request = client.get(url)
        .map(|res| {
            assert_eq!(res.status(), hyper::Ok);
        });

    // request is a Future, futures are lazy, so must explicitly run
    core.run(request).unwrap();
}

In Cargo.toml:

[dependencies]
hyper = "0.11"
tokio-core = "0.1"
futures = "0.1"

For posterity I've left my original answer below, but see above for an update for Rust 1.19 (latest stable version as of this writing).

I believe what you're looking for is in the standard library. now in rust-http and Chris Morgan's answer is the standard way in current Rust for the foreseeable future. ~~I'm not sure how far I can take you (and hope I'm not taking you the wrong direction!), but you'll want something like:~~

// Rust 0.6 -- old code
/*
extern mod std;

use std::net_ip;
use std::uv;

fn main() {
    let iotask = uv::global_loop::get();
    let result = net_ip::get_addr("www.duckduckgo.com", &iotask);

    io::println(fmt!("%?", result));
 }
 */

As for encoding, there are some examples in the unit tests in src/libstd/net_url.rs.

Using curl bindings. Stick this in your Cargo.toml:

[dependencies.curl]
git = "https://github.com/carllerche/curl-rust"

...and this in the src/main.rs:

extern crate curl;

use curl::http;

fn main(){
  let resp = http::handle()
    .post("http://localhost:3000/login", "username=dude&password=sikrit")
    .exec().unwrap();

  println!("code={}; headers={}; body={}",
    resp.get_code(), resp.get_headers(), resp.get_body());    

}