Create an echo server

This tutorial will guide you through creating a simple echo server in Rust.

Install Rust

Run

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

to install the Rust toolchain.

Run

cargo

to verify if it has been installed successfully.

Create the echo server

Run

cargo new --bin echo-server && cd echo-server

to create a new Rust project for the echo server.

Run

cat > src/main.rs <<EOF
use std::env;
use std::io::{Read, Write};
use std::net::{TcpListener, TcpStream};

fn handle(mut stream: TcpStream) {
    println!("Connection opened: {}", stream.peer_addr().unwrap());
    let mut buf = [0; 512];
    loop {
        match stream.read(&mut buf) {
            Ok(0) => {
                println!("Connection closed: {}", stream.peer_addr().unwrap());
                return;
            }
            Ok(n) => {
                if let Err(e) = stream.write_all(&buf[..n]) {
                    eprintln!("Failed to write to socket: {}", e);
                    return;
                }
            }
            Err(e) => {
                eprintln!("Failed to read from socket: {}", e);
                break;
            }
        }
    }
}

fn main() -> std::io::Result<()> {
    let port = env::var("PORT").unwrap_or_else(|_| "8080".to_string());
    let addr = format!("0.0.0.0:{}", port);
    
    let listener = TcpListener::bind(&addr)?;
    println!("Echo server listening on {}", addr);

    listener
        .incoming()
        .try_for_each(|stream| -> Result<_, std::io::Error> {
            let stream = stream?;
            std::thread::spawn(move || {
                handle(stream);
            });
            Ok(())
        })
}
EOF

to add the code for the echo server. Feel free to pause and understand how the echo server works.

Test the echo server locally

Run

cargo run

to run the echo server locally.

In a new terminal, run

nc 127.0.0.1 8080

to connect to the echo server. Type anything in the terminal and the echo server should echo it back to you. Type Ctrl+C to exit both programs.

You can also run the echo server on a different port by specifying the PORT env variable by running

PORT=5000 cargo run

In a new terminal, you can access the server just as above but on 5000 port using

nc 127.0.0.1 5000

Now that you have created the application, the next step is to package it into a Docker image.