[TOC] ### Building a Single-Threaded Web Server #### Listening to the TCP Connection ```rust use std::net::TcpListener; fn main() { let listener = TcpListener::bind("127.0.0.1:80").unwrap(); for stream in listener.incoming() { let stream = stream.unwrap(); println!("Connection established!"); } } ```  #### Reading the Request ```rust use std::io::prelude::*; use std::net::TcpListener; use std::net::TcpStream; fn main() { let listener = TcpListener::bind("127.0.0.1:80").unwrap(); for stream in listener.incoming() { let stream = stream.unwrap(); handle_connection(stream); } } fn handle_connection(mut stream: TcpStream) { let mut buffer = [0; 1024]; stream.read(&mut buffer).unwrap(); println!("Request: {}", String::from_utf8_lossy(&buffer[..])); } ```  #### Writing a Response ```rust use std::io::prelude::*; use std::net::TcpListener; use std::net::TcpStream; fn main() { let listener = TcpListener::bind("127.0.0.1:80").unwrap(); for stream in listener.incoming() { let stream = stream.unwrap(); handle_connection(stream); } } fn handle_connection(mut stream: TcpStream) { let mut buffer = [0; 1024]; stream.read(&mut buffer).unwrap(); let response = "HTTP/1.1 200 OK\r\n\r\n"; stream.write(response.as_bytes()).unwrap(); stream.flush().unwrap(); } ``` #### Validating the Request and Selectively Responding ```rust use std::net::{TcpListener, TcpStream}; use std::io::prelude::*; use std::fs; fn main() { let listener = TcpListener::bind("127.0.0.1:80").unwrap(); for stream in listener.incoming() { let stream = stream.unwrap(); handle_connection(stream); } } fn handle_connection(mut stream: TcpStream) { let mut buffer = [0; 1024]; stream.read(&mut buffer).unwrap(); let get = b"GET / HTTP/1.1\r\n"; if buffer.starts_with(get) { let contents = fs::read_to_string("hello.html").unwrap(); let response = format!( "HTTP/1.1 200 OK\r\nContent-Length: {}\r\n\r\n{}", contents.len(), contents ); stream.write(response.as_bytes()).unwrap(); stream.flush().unwrap(); } else { let status_line = "HTTP/1.1 404 NOT FOUND"; let contents = fs::read_to_string("404.html").unwrap(); let response = format!( "{}\r\nContent-Length: {}\r\n\r\n{}", status_line, contents.len(), contents ); stream.write(response.as_bytes()).unwrap(); stream.flush().unwrap(); } } ``` #### A Touch of Refactoring ```rust use std::net::{TcpListener, TcpStream}; use std::io::prelude::*; use std::fs; fn main() { let listener = TcpListener::bind("127.0.0.1:80").unwrap(); for stream in listener.incoming() { let stream = stream.unwrap(); handle_connection(stream); } } fn handle_connection(mut stream: TcpStream) { // --snip-- let mut buffer = [0; 1024]; stream.read(&mut buffer).unwrap(); let get = b"GET / HTTP/1.1\r\n"; let (status_line, filename) = if buffer.starts_with(get) { ("HTTP/1.1 200 OK", "hello.html") } else { ("HTTP/1.1 404 NOT FOUND", "404.html") }; let contents = fs::read_to_string(filename).unwrap(); let response = format!( "{}\r\nContent-Length: {}\r\n\r\n{}", status_line, contents.len(), contents ); stream.write(response.as_bytes()).unwrap(); stream.flush().unwrap(); } ```