c++ – How does nginx achieve zero TIME_WAIT sockets under load testing on Windows?

While implementing a C++ HTTP server on Windows, I’m investigating how nginx handles socket cleanup. Using netstat, I observe that after handling multiple concurrent requests with hey benchmarking tool, nginx maintains zero sockets in TIME_WAIT state.

My understanding of TCP socket states:

• TIME_WAIT occurs on the connection-terminating endpoint
• When server initiates close, its socket enters TIME_WAIT
• When client initiates close, client socket enters TIME_WAIT
• TIME_WAIT typically lasts 2MSL (Maximum Segment Lifetime)

My current implementation:

• Standard Windows socket API (Winsock2) with I/O CP
• Proper socket cleanup with closesocket()
• SO_REUSEADDR enabled
• Basic HTTP request handling

Despite these measures, my server accumulates sockets in TIME_WAIT when closing connections. However, nginx somehow avoids this entirely.

What techniques or socket configurations does nginx employ to achieve zero TIME_WAIT sockets? Are there specific Windows-related optimizations in play?

I’ve already investigated:

• Connection keepalive settings
• SO_LINGER socket options
• TCP_NODELAY
• Various client-initiated close strategies