taskFaker.advanceUntil(ns(500L))
    server.processNextFrame() // Ping.
    client.processNextFrame() // Pong.
    taskFaker.advanceUntil(ns(1000L))
    server.processNextFrame() // Ping.
    client.processNextFrame() // Pong.
    taskFaker.advanceUntil(ns(1500L))
    server.processNextFrame() // Ping.
    client.processNextFrame() // Pong.
  }

  @Test

If you just don't know, use normal `def`.

---

**Note**: You can mix `def` and `async def` in your *path operation functions* as much as you need and define each one using the best option for you. FastAPI will do the right thing with them.

Anyway, in any of the cases above, FastAPI will still work asynchronously and be extremely fast.

But by following the steps above, it will be able to do some performance optimizations.

## Technical Details

    length: Int,
    flags: Int,
    streamId: Int,
  ) {
    if (length != 8) throw IOException("TYPE_PING length != 8: $length")
    if (streamId != 0) throw IOException("TYPE_PING streamId != 0")
    val payload1 = source.readInt()
    val payload2 = source.readInt()
    val ack = flags and FLAG_ACK != 0
    handler.ping(ack, payload1, payload2)
  }

  @Throws(IOException::class)
  private fun readGoAway(

        sink.writeInt(settings[i])
      }
      sink.flush()
    }
  }

  /**
   * Send a connection-level ping to the peer. `ack` indicates this is a reply. The data in
   * `payload1` and `payload2` opaque binary, and there are no rules on the content.
   */
  @Throws(IOException::class)
  fun ping(
    ack: Boolean,
    payload1: Int,
    payload2: Int,
  ) {
    this.withLock {

    assertThat(response.protocol).isEqualTo(protocol)

    // Confirm a single ping was sent and received, and its reply was sent and received.
    val logs = testLogHandler.takeAll()
    assertThat(countFrames(logs, "FINE: >> 0x00000000     8 PING          "))
      .isEqualTo(1)
    assertThat(countFrames(logs, "FINE: << 0x00000000     8 PING          "))
      .isEqualTo(1)

    payload2: Int,
  ) {
    try {
      writer.ping(reply, payload1, payload2)
    } catch (e: IOException) {
      failConnection(e)
    }
  }

  /** For testing: sends a ping and waits for a pong. */
  @Throws(InterruptedException::class)
  fun writePingAndAwaitPong() {
    writePing()
    awaitPong()
  }

  /** For testing: sends a ping to be awaited with [awaitPong]. */

    val settings1 = Settings()
    settings1[Settings.MAX_CONCURRENT_STREAMS] = maxConcurrentStreams
    peer.sendFrame().settings(settings1)
    peer.acceptFrame() // ACK
    peer.sendFrame().ping(false, 2, 0)
    peer.acceptFrame() // PING
    peer.play()

    // Play it back.
    val connection =
      Http2Connection.Builder(true, TaskRunner.INSTANCE)
        .socket(peer.openSocket())

    }
  }

  @Test fun emptyPingCallsCallback() {
    data.write("8900".decodeHex()) // Empty ping
    clientReader.processNextFrame()
    callback.assertPing(EMPTY)
  }

  @Test fun pingCallsCallback() {
    data.write("890548656c6c6f".decodeHex()) // Ping with "Hello"
    clientReader.processNextFrame()
    callback.assertPing("Hello".encodeUtf8())
  }

Nhưng mặc định, tất cả **đều hoạt động**.

### Validation

* Validation cho đa số (hoặc tất cả?) **các kiểu dữ liệu** Python, bao gồm:
    * JSON objects (`dict`).
    * Mảng JSON (`list`) định nghĩa kiểu dữ liệu từng phần tử.
    * Xâu (`str`), định nghĩa độ dài lớn nhất, nhỏ nhất.

    )
    val openAtNanos = System.nanoTime()
    newWebSocket()
    clientListener.assertOpen()
    clientListener.assertFailure(
      SocketTimeoutException::class.java,
      "sent ping but didn't receive pong within 500ms (after 0 successful ping/pongs)",
    )
    latch.countDown()
    val elapsedUntilFailure = System.nanoTime() - openAtNanos
    assertThat(TimeUnit.NANOSECONDS.toMillis(elapsedUntilFailure).toDouble())