[bluetomcat]

The traditional Unix IO model broke with the Berkeley sockets API introduced in 1982. The obvious "Unix" way to handle a TCP connection concurrently was to fork() a separate process servicing the connection synchronously, but that doesn't scale well with many connections. Then they introduced non-blocking sockets and select(), then poll(), and now Linux has its own epoll. All these "async programming models" are ultimately based on that system API.