阻塞 v.s. 非阻塞
简言之,应用程序发出的请求能否得到马上返回应答,不能需等待的则为 阻塞, 否则为 非阻塞.
同步 v.s. 异步
A synchronous I/O operation causes the requesting process to be blocked until that I/O operation completes;
An asynchronous I/O operation does not cause the requesting process to be blocked;