Sumit Kumar - Projects

No libwebsockets, no Boost.Asio, no framework doing the protocol work for you — just poll(), raw POSIX sockets, and the RFC 6455 spec. I wanted to actually understand what a WebSocket connection is underneath the abstraction, so I wrote the handshake and frame parser by hand in C++.

The HTTP side (http.hpp/http.cpp) handles the initial upgrade request just enough to extract the Sec-WebSocket-Key header. From there, ws.hpp/ws.cpp takes over: websocket_accept() computes the required Sec-WebSocket-Accept response key (base64-encoded SHA-1 of the client key plus the magic GUID from the spec), try_parse_frame() parses the binary frame format directly off the socket buffer — FIN bit, opcode, payload — and make_text_frame() builds outgoing frames the same way, no serialization library involved.

The server itself (chat_server.cpp) runs a single-threaded poll() event loop over all connected sockets rather than spawning a thread per client, which keeps it simple and avoids most classic concurrency bugs by construction. A handful of small, deliberate design choices round it out:

• A token-bucket rate limiter per connection (8-token burst, refilling at 4/sec) so one chatty client can't flood everyone else
• Message history — the last 50 messages are kept and replayed to newly connected clients, persisted to a local data/ directory so history survives a restart
• A minimal static file server for the bundled public/ web client (plain HTML/CSS/JS) so you can open a browser tab and actually chat, no separate frontend build step required

There's also a Python test client (test_client.py) for scripted connection/load testing without needing a browser at all. The whole thing builds with a plain Makefile — no build system beyond what a C++ compiler already gives you.