Improving .NET Network Performance with Kernel Events

I recently rebuilt our TCP/UDP network server library to handle high-load scenarios. The initial thread-per-client approach worked but hit memory limits at around 3,000 simultaneous connections.

The solution? Kernel events. Using IOCP (Windows), epoll (Linux), and kqueue (FreeBSD), we let the kernel notify our program when new data arrives instead of polling. With a 128-byte pre-allocated buffer and some BeginReceive calls, the changes were minimal.

The results exceeded expectations: from a 10,000 connection target, we achieved 60,000 simultaneous connections with near-zero CPU usage and instant response times. This proves Mono/.NET’s capability for high-performance network servers.