Spawning with TcpStream leads to 10061 ConnectionRefused - rust

Question

I'm trying to make a simple host which can handle multiple streams (similar to the example given in https://tokio.rs/tokio/tutorial):
use std::{error::Error, time::Duration};
use tokio::{
io::{AsyncReadExt, AsyncWriteExt},
net::{TcpListener, TcpStream},
time::sleep,
};
type GenericResult<T> = Result<T, Box<dyn Error>>;
#[tokio::main]
async fn main() {
const ADDRESS: &str = "127.0.0.1:8080";
let listener = TcpListener::bind(ADDRESS).await.unwrap();
tokio::spawn(async { host(listener) });
let mut stream = TcpStream::connect(ADDRESS).await.unwrap();
stream.write_all(b"testing").await.unwrap();
}
async fn host(listener: TcpListener) -> GenericResult<()> {
loop {
let (stream, _) = listener.accept().await?;
println!("new connection");
tokio::spawn(async { process(stream).await.unwrap() });
}
async fn process(mut stream: TcpStream) -> GenericResult<()> {
// Reads from stream
let mut buffer = Vec::with_capacity(128);
let mut position = 0;
loop {
// Read from stream into buffer
let n = stream.read(&mut buffer[position..]).await?;
// Advance position
position += n;
// Print buffer
println!("buffer: {:?}", buffer);
sleep(Duration::from_millis(100)).await;
}
}
}
But when running this I encounter:
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Os { code: 10061, kind: ConnectionRefused, message: "No connection could be made because the target machine actively refused it." }', src\main.rs:12:56
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
Any help would be really appreciated here.
Specifically why my implementation here differs (in functionality) from a working implementation in https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=5b944a8c4703d438d48ef5e556f1fc08
cargo --version --verbose:
cargo 1.60.0 (d1fd9fe2c 2022-03-01)
release: 1.60.0
commit-hash: d1fd9fe2c40a1a56af9132b5c92ab963ac7ae422
commit-date: 2022-03-01
host: x86_64-pc-windows-msvc
libgit2: 1.3.0 (sys:0.13.23 vendored)
libcurl: 7.80.0-DEV (sys:0.4.51+curl-7.80.0 vendored ssl:Schannel)
os: Windows 10.0.22000 (Windows 10 Pro) [64-bit]
With tokio = {version="1.18.0",features=["full"]}

Answer 1

Define the stream before you start listening on it.
use std::{error::Error, time::Duration};
use tokio::{
io::{AsyncReadExt, AsyncWriteExt},
net::{TcpListener, TcpStream},
time::sleep,
};
type GenericResult<T> = Result<T, Box<dyn Error>>;
#[tokio::main]
async fn main() {
const ADDRESS: &str = "127.0.0.1:8080";
let listener = TcpListener::bind(ADDRESS).await.unwrap();
let mut stream = TcpStream::connect(ADDRESS).await.unwrap();
tokio::spawn(async { host(listener) });
stream.write_all(b"testing").await.unwrap();
}
async fn host(listener: TcpListener) -> GenericResult<()> {
loop {
let (stream, _) = listener.accept().await?;
println!("new connection");
tokio::spawn(async { process(stream).await.unwrap() });
}
async fn process(mut stream: TcpStream) -> GenericResult<()> {
// Reads from stream
let mut buffer = Vec::with_capacity(128);
let mut position = 0;
loop {
// Read from stream into buffer
let n = stream.read(&mut buffer[position..]).await?;
// Advance position
position += n;
// Print buffer
println!("buffer: {:?}", buffer);
sleep(Duration::from_millis(100)).await;
}
}
}