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lbernicklbernick
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More beginner-friendly TCP server example (#102)
I wanted to write an example to help guide people new to asynchronous programming, with fewer external dependencies (as some people requested in #66). The example starts with the [single threaded TCP server from the Rust book](https://doc.rust-lang.org/book/ch20-01-single-threaded.html) and uses async functionality to add concurrency. The example goes through: - some examples of blocking code and how to make them non blocking (should address #64 as well) - spawning tasks vs using combinators to run them concurrently on a single thread - testing code by creating mocks and implementing async read/write traits for the mocks
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-199
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27 files changed

+597
-199
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‎ci/dictionary.txt

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@@ -24,6 +24,8 @@ FutOne
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FutTwo
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FuturesUnordered
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GenFuture
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gRPC
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html
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http
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Hyper's
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impl
@@ -33,8 +35,13 @@ IoBlocker
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IOCP
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IoObject
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kqueue
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localhost
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LocalExecutor
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metadata
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MockTcpStream
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multi
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multithreaded
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multithreading
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Mutex
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MyError
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MyFut
@@ -51,15 +58,18 @@ proxying
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pseudocode
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ReadIntoBuf
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recognise
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refactor
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RefCell
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repurposed
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requeue
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ResponseFuture
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reusability
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runtime
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runtimes
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rustc
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rustup
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SimpleFuture
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smol
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SocketRead
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SomeType
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spawner
@@ -69,6 +79,8 @@ struct
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subfuture
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subfutures
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subpar
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TcpListener
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TcpStream
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threadpool
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TimerFuture
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TODO

‎examples/01_05_http_server/Cargo.toml

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‎examples/01_05_http_server/src/lib.rs

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‎examples/02_04_executor/src/lib.rs

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// ANCHOR: imports
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use {
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futures::{
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future::{FutureExt, BoxFuture},
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task::{ArcWake, waker_ref},
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future::{BoxFuture, FutureExt},
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task::{waker_ref, ArcWake},
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},
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std::{
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future::Future,
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sync::mpsc::{sync_channel, Receiver, SyncSender},
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sync::{Arc, Mutex},
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sync::mpsc::{sync_channel, SyncSender, Receiver},
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task::{Context, Poll},
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time::Duration,
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},
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// Implement `wake` by sending this task back onto the task channel
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// so that it will be polled again by the executor.
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let cloned = arc_self.clone();
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arc_self.task_sender.send(cloned).expect("too many tasks queued");
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arc_self
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.task_sender
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.send(cloned)
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.expect("too many tasks queued");
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}
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}
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// ANCHOR_END: arcwake_for_task
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// ANCHOR_END: main
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#[test]
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fn run_main() { main() }
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fn run_main() {
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main()
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}

‎examples/08_01_sync_tcp_server/404.html

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<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="utf-8">
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<title>Hello!</title>
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</head>
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<body>
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<h1>Oops!</h1>
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<p>Sorry, I don't know what you're asking for.</p>
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</body>
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</html>

‎examples/08_01_sync_tcp_server/Cargo.toml

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[package]
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name = "sync_tcp_server"
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version = "0.1.0"
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authors = ["Your Name <[email protected]"]
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edition = "2018"
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# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
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[dependencies]

‎examples/08_01_sync_tcp_server/hello.html

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<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="utf-8">
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<title>Hello!</title>
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</head>
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<body>
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<h1>Hello!</h1>
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<p>Hi from Rust</p>
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</body>
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</html>

‎examples/08_01_sync_tcp_server/src/main.rs

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use std::fs;
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use std::io::prelude::*;
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use std::net::TcpListener;
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use std::net::TcpStream;
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fn main() {
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// Listen for incoming TCP connections on localhost port 7878
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let listener = TcpListener::bind("127.0.0.1:7878").unwrap();
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// Block forever, handling each request that arrives at this IP address
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for stream in listener.incoming() {
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let stream = stream.unwrap();
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handle_connection(stream);
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}
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}
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fn handle_connection(mut stream: TcpStream) {
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// Read the first 1024 bytes of data from the stream
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let mut buffer = [0; 1024];
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stream.read(&mut buffer).unwrap();
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let get = b"GET / HTTP/1.1\r\n";
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// Respond with greetings or a 404,
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// depending on the data in the request
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let (status_line, filename) = if buffer.starts_with(get) {
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("HTTP/1.1 200 OK\r\n\r\n", "hello.html")
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} else {
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("HTTP/1.1 404 NOT FOUND\r\n\r\n", "404.html")
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};
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let contents = fs::read_to_string(filename).unwrap();
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// Write response back to the stream,
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// and flush the stream to ensure the response is sent back to the client
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let response = format!("{}{}", status_line, contents);
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stream.write(response.as_bytes()).unwrap();
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stream.flush().unwrap();
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}

‎examples/08_02_async_tcp_server/Cargo.toml

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[package]
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name = "async_tcp_server"
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version = "0.1.0"
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authors = ["Your Name <[email protected]"]
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edition = "2018"
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# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
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[dependencies.async-std]
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version = "1.6"
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features = ["attributes"]

‎examples/08_02_async_tcp_server/src/main.rs

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use std::net::TcpListener;
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use std::net::TcpStream;
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// ANCHOR: main_func
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#[async_std::main]
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async fn main() {
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let listener = TcpListener::bind("127.0.0.1:7878").unwrap();
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for stream in listener.incoming() {
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let stream = stream.unwrap();
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// Warning: This is not concurrent!
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handle_connection(stream).await;
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}
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}
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// ANCHOR_END: main_func
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// ANCHOR: handle_connection_async
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async fn handle_connection(mut stream: TcpStream) {
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//<-- snip -->
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}
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// ANCHOR_END: handle_connection_async

‎examples/08_03_slow_request/Cargo.toml

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[package]
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name = "slow_request"
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version = "0.1.0"
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authors = ["Your Name <[email protected]"]
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edition = "2018"
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# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
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[dependencies.async-std]
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version = "1.6"
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features = ["attributes"]

‎examples/08_03_slow_request/src/main.rs

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use std::fs;
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use std::io::{Read, Write};
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use std::net::TcpListener;
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use std::net::TcpStream;
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use std::time::Duration;
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#[async_std::main]
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async fn main() {
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let listener = TcpListener::bind("127.0.0.1:7878").unwrap();
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for stream in listener.incoming() {
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let stream = stream.unwrap();
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handle_connection(stream).await;
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}
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}
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// ANCHOR: handle_connection
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use async_std::task;
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async fn handle_connection(mut stream: TcpStream) {
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let mut buffer = [0; 1024];
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stream.read(&mut buffer).unwrap();
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let get = b"GET / HTTP/1.1\r\n";
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let sleep = b"GET /sleep HTTP/1.1\r\n";
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let (status_line, filename) = if buffer.starts_with(get) {
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("HTTP/1.1 200 OK\r\n\r\n", "hello.html")
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} else if buffer.starts_with(sleep) {
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task::sleep(Duration::from_secs(5)).await;
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("HTTP/1.1 200 OK\r\n\r\n", "hello.html")
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} else {
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("HTTP/1.1 404 NOT FOUND\r\n\r\n", "404.html")
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};
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let contents = fs::read_to_string(filename).unwrap();
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let response = format!("{}{}", status_line, contents);
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stream.write(response.as_bytes()).unwrap();
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stream.flush().unwrap();
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}
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// ANCHOR_END: handle_connection

‎examples/08_04_concurrent_tcp_server/Cargo.toml

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[package]
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name = "concurrent_tcp_server"
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version = "0.1.0"
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authors = ["Your Name <[email protected]"]
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edition = "2018"
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# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
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[dependencies]
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futures = "0.3"
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[dependencies.async-std]
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version = "1.6"
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features = ["attributes"]

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