Single threaded Rust server from the Rust Programming Language 2018 book

single_threaded_rust_server.rs

use std::io::prelude::*; // Traits that let us read and write to the stream
use std::net::TcpStream;
use std::net::TcpListener;
use std::fs; // Bring standard library File into scope

fn main() {
    // bind returns a new TcpListener instances
    // Connecting to a port to listen to is also called "binding to a port"
    // bind returns a Result<T, E>
    // unwrap will stop the program if errors occur
    let listener = TcpListener::bind("127.0.0.1:7878").unwrap();

    // Nonadministrators can only listen on ports higher than 1024

    // incoming returns an iterator that gives a sequence of TcpStream type streams
    // A single stream represents an open connection between client and server
    // A connection is the full request and response process where a client connects to the server,
    // the server generates a response, and the server closes the connection.
    // Here we are iterating over connection attempts, not actual connections.
    for stream in listener.incoming() {
        // TcpStream instance keeps track of what data it returns to us internally. This means that
        // it might read mroe data than we asked for and save that data for the next time we ask.
        let stream = stream.unwrap();
        handle_connection(stream);
    }
}

fn handle_connection(mut stream: TcpStream) {
    // Declare buffer on the stack to hold the data that is read in
    let mut buffer = [0; 512]; // 512 bytes
    // Read bytes from the TcpStream and put them into the buffer
    stream.read(&mut buffer).unwrap();

    // Transform the variable into a byte string
    let get = b"GET / HTTP/1.1\r\n";

    // Return values in a tuple
    // Destructuring assigns values using a pattern in the let statement
    let (status_line, filename) =  if buffer.starts_with(get) {
        ("HTTP/1.1 200 Ok\r\n\r\n", "public/index.html")
    } else {
        ("HTTP/1.1 404 NOT FOUND\r\n\r\n", "public/404.html")
    };

    let contents = fs::read_to_string(filename).unwrap();
    let response = format!("{}{}", status_line, contents);

    // The write method on stream takes a &[u8] and sends those bytes directly down the
    // connection
    stream.write(response.as_bytes()).unwrap();
    // Flush waits and prevents the program from continuing until all the bytes are written to
    // the connection.
    // The TcpStream type contains an internal buffer to minimize calls tot he underlying OS.
    stream.flush().unwrap();

    // Convert bytes in buffer to a string to print it
    // Lossy means invalid UTF-8 sequences are replaced with the replacement character U+FFFD
    // Replacement characters will be in the buffer for characters that aren't filled by request
    // data
    // println!("Request: {}", String::from_utf8_lossy(&buffer[..]));
}