+-+ 阻 塞 I/O (BIO)
                                     |
                                     +-+ 非 阻 塞 I/O (NIO)
                                     |
                  +----+ 同 步 I/O +--+
                  |                  |
                  |                  +-+ I/O 多 路 复 用
                  |                  |
                  |                  +-+ 信 号 驱 动 I/O
    I/O 模 型  +---+
                  |
                  |
                  |                  +-+ Linux (AIO)
                  |                  |         (io_uring)
                  +----+ 异 步 I/O +--+
                                     |
                                     +-+ windows (IOCP)

    ```

    ```text
    Application               kernel
    +---------+            +-----------+  +---+
    |         |   syscall  | no        |      |
    |   Read  | +--------> | datagram  |      |
    | recvfrom|            | ready     |      |
    |         |            |    +      |      +-+ wait for
    |         |            |    |      |      +-+ data
    |         |            |    v      |      |
    |         |            | datagram  |      |
    |         |            | ready     |  +---+
    |         |            |           |
    |         |            | copy      |  +---+
    |         |            | datagram  |      |
    |process  |            |    +      |      +-+ copy data
    |datagram |   return   |    |      |      +-+ from kernel to user
    |         | <--------+ |    v      |      |
    |         |            |  copy     |  +---+
    |         |            |  complete |
    +---------+            +-----------+
    ```