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90 lines
3.1 KiB
Rust
90 lines
3.1 KiB
Rust
//! A "hello world" echo server with Tokio
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//!
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//! This server will create a TCP listener, accept connections in a loop, and
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//! write back everything that's read off of each TCP connection.
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//!
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//! Because the Tokio runtime uses a thread pool, each TCP connection is
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//! processed concurrently with all other TCP connections across multiple
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//! threads.
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//!
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//! To see this server in action, you can run this in one terminal:
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//!
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//! cargo run --example echo
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//!
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//! and in another terminal you can run:
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//!
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//! cargo run --example connect 127.0.0.1:8080
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//!
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//! Each line you type in to the `connect` terminal should be echo'd back to
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//! you! If you open up multiple terminals running the `connect` example you
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//! should be able to see them all make progress simultaneously.
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#![feature(async_await)]
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#![warn(rust_2018_idioms)]
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use tokio;
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use tokio::io::{AsyncReadExt, AsyncWriteExt};
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use tokio::net::TcpListener;
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use std::env;
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use std::error::Error;
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use std::net::SocketAddr;
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use tracing::{debug, error, info, warn};
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#[tokio::main]
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async fn main() -> Result<(), Box<dyn Error>> {
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let subscriber = tracing_fmt::FmtSubscriber::builder().finish();
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tracing::subscriber::set_global_default(subscriber)?;
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// Allow passing an address to listen on as the first argument of this
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// program, but otherwise we'll just set up our TCP listener on
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// 127.0.0.1:8080 for connections.
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let addr = env::args().nth(1).unwrap_or("127.0.0.1:3000".to_string());
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let addr = addr.parse::<SocketAddr>()?;
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// Next up we create a TCP listener which will listen for incoming
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// connections. This TCP listener is bound to the address we determined
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// above and must be associated with an event loop.
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let mut listener = TcpListener::bind(&addr)?;
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info!("Listening on: {}", addr);
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loop {
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// Asynchronously wait for an inbound socket.
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let (mut socket, peer_addr) = listener.accept().await?;
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info!("Got connection from: {}", peer_addr);
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// And this is where much of the magic of this server happens. We
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// crucially want all clients to make progress concurrently, rather than
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// blocking one on completion of another. To achieve this we use the
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// `tokio::spawn` function to execute the work in the background.
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//
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// Essentially here we're executing a new task to run concurrently,
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// which will allow all of our clients to be processed concurrently.
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tokio::spawn(async move {
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let mut buf = [0; 1024];
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// In a loop, read data from the socket and write the data back.
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loop {
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let n = socket
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.read(&mut buf)
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.await
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.expect("failed to read data from socket");
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if n == 0 {
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return;
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}
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socket
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.write_all(&buf[0..n])
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.await
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.expect("failed to write data to socket");
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info!(message = "echo'd data", peer_addr = ?peer_addr, size = n);
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}
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});
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}
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}
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