Developer benchmarks seven C TCP server designs to show real I/O scaling limits

A developer rebuilt a simple C echo server seven times — from a basic blocking design to epoll — to measure how each approach handles concurrent connections. The experiment was motivated by a 1.51-second stall observed when one idle client blocked all others on a single-threaded blocking server. Each iteration exposed a specific bottleneck, such as select's hard FD_SETSIZE cap of 1024 file descriptors and its O(n) scan cost per wakeup. The project targets Dan Kegel's classic C10K problem of serving ten thousand simultaneous clients on one machine. All seven versions were written without external libraries, benchmarked on macOS in June 2026, and published on GitHub.