rust-backend-scratch

A TCP echo server written in Rust from scratch — no framework, no Tokio, just raw Linux syscalls via libc. Built to understand how a backend server actually works below the framework layer.

What it does

Accepts multiple client connections at once on port 8080, echoes back whatever each client sends. Single-threaded, non-blocking, event-driven.

How it works

Uses an epoll event loop instead of one-thread-per-connection:

• Creates a non-blocking listening socket (socket → bind → listen)
• Registers it with an epoll instance
• One thread sleeps in epoll_wait until any socket has activity
• On activity: accepts new clients (registering each into epoll) or reads/echoes data from existing ones
• Idles at ~0% CPU when no clients are active (sleeps, doesn't poll)

This is the same core model behind nginx and Node.js — a single thread handling many connections by only touching the ones that are ready.

Run it

cargo run

Then in another terminal:

nc localhost 8080

Type anything — it echoes back. Open multiple nc sessions to see concurrent clients handled by one thread.

Status

Working: concurrent echo over TCP.
Next: HTTP/1.1 request parsing (GET → response).

Built with

Rust, raw libc syscalls (socket, bind, listen, accept, epoll_*, read, write), unsafe FFI. Linux only (epoll is Linux-specific).