Capstone: tiny HTTP server

The spec

Build tinyhttp: a server on 127.0.0.1 port 7878 that answers three cases. The root path serves home, about serves about, and anything else gets a 404 page. Hand-built responses, no framework, no async.

Success means a client prints home for the root path and not found for unknown paths. The sections below add routing, responses, and a client test in that order.

Route GET paths

Routing is a pure function from path to body. Match the three cases and return string slices so no allocation happens yet:

fn route(path: &str) -> &str { match path { "/" => "home page", "/about" => "about page", _ => "not found", } }

Hand-built responses

HTTP answers are status line plus headers plus blank line plus body. The format macro assembles all four while Content-Length comes from the body itself:

fn response(body: &str) -> String { format!("HTTP/1.1 200 OK\r\nContent-Length: {}\r\n\r\n{}", body.len(), body) }

One function builds every 200 reply. A 404 reply needs only a different status line, which is a good first exercise.

Test with TCP client

Prove the server talks HTTP with a tiny client test. Connect, send a GET request, read everything, and assert the status code made it back:

use std::io::{Read, Write}; use std::net::TcpStream; #[test] fn serves_home() { let mut s = TcpStream::connect("127.0.0.1:7878").unwrap(); s.write_all(b"GET / HTTP/1.0\r\n\r\n").unwrap(); let mut buf = String::new(); s.read_to_string(&mut buf).unwrap(); assert!(buf.contains("200")); }

Start the server first, then run cargo test. A green test means a real socket carried a real request and a real reply.

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Article author: Arthur Isaev