cWS — Tiny WebSocket Echo Server & Client

cWS implements a full WebSocket server and client from scratch in C with zero external dependencies beyond Winsock2 (built into Windows). The server listens on ws://127.0.0.1:8080 and accepts a single client connection; the client can run in interactive mode (read stdin and echo back responses) or benchmark mode (send and measure round-trip time). Both encode the WebSocket handshake using inline SHA-1 and Base64, avoiding a dependency on OpenSSL or similar.

The benchmark mode is the main draw. The client can pump N messages of configurable size through the connection, timing each round-trip with QueryPerformanceCounter (Windows high-resolution timer). It then sorts the RTTs and reports min, max, average, p50, p95 latency, messages per second, and throughput in MB/s. On localhost Windows, a 64-byte payload achieves ~19,793 msgs/sec with 50.5µs average RTT; a 16 KB payload hits ~7,942 msgs/sec with 125.8µs latency.

Intended for measuring WebSocket performance overhead on Windows without the complexity of a full framework or test harness. The single-file approach makes it trivial to compile and modify; no headers to hunt down, no build configuration beyond a batch script. Useful for performance debugging or as a baseline for what bare-metal Winsock2 WebSocket can sustain.