* known as the XON code used for software flow control in serial communications. The main use is
   * restarting the transmission after the communication has been stopped by the XOFF control code.
   *
   * @since 8.0
   */
  public static final byte XON = 17; // aka DC1

  /**

    assertEquals(control(NE, 1), entry(NE, 1));
    assertFalse(control(NE, 1).equals(entry(NE, 2)));
    assertFalse(entry(NE, 1).equals(control("bar", 1)));
    assertFalse(entry(NE, 1).equals(new Object()));
    assertFalse(entry(NE, 1).equals(null));
  }

  public void testHashCode() {
    assertEquals(control("foo", 1).hashCode(), entry("foo", 1).hashCode());

        .Builder()
        .addHeader("Cache-Control: max-age=60")
        .body("ABC")
        .build(),
    )
    server.enqueue(
      MockResponse
        .Builder()
        .addHeader("Cache-Control: max-age=60")
        .body("DEF")
        .build(),
    )
    server.enqueue(
      MockResponse
        .Builder()
        .addHeader("Cache-Control: max-age=60")
        .body("DEFa")

    assertEquals(control(NE, 1), entry(NE, 1));
    assertFalse(control(NE, 1).equals(entry(NE, 2)));
    assertFalse(entry(NE, 1).equals(control("bar", 1)));
    assertFalse(entry(NE, 1).equals(new Object()));
    assertFalse(entry(NE, 1).equals(null));
  }

  public void testHashCode() {
    assertEquals(control("foo", 1).hashCode(), entry("foo", 1).hashCode());

    val headers =
      Headers.headersOf(
        "cache-control",
        "no-store",
        "Cache-Control",
        "no-cache",
      )
    val headerMap = headers.toMultimap()
    assertThat(headerMap["cache-control"]!!.size).isEqualTo(2)
    assertThat(headerMap["Cache-Control"]!!.size).isEqualTo(2)
  }

    val headers = headersOf("Cache-Control", "max-age=12", "Pragma", "must-revalidate", "Pragma", "public")
    val cacheControl = parse(headers)
    assertThat(cacheControl.toString()).isEqualTo("max-age=12, public, must-revalidate")
  }

  @Test
  fun parseCacheControlHeaderValueIsRetained() {
    val value = "max-age=12"
    val headers = headersOf("Cache-Control", value)
    val cacheControl = parse(headers)

    assertTrue(foo1.equals(foo1));
    assertEquals(control("foo", 1), foo1);
    assertEquals(control("bar", 2), entry("bar", 2));
    assertFalse(control("foo", 1).equals(entry("foo", 2)));
    assertFalse(foo1.equals(control("bar", 1)));
    assertFalse(foo1.equals(new Object()));
    assertFalse(foo1.equals(null));
  }

  public void testEqualsNull() {
    assertEquals(control(NK, 1), entry(NK, 1));

    headers = {
        "Origin": "https://localhost.tiangolo.com",
        "Access-Control-Request-Method": "GET",
        "Access-Control-Request-Headers": "X-Example",
    }
    response = client.options("/", headers=headers)
    assert response.status_code == 200, response.text
    assert response.text == "OK"
    assert (
        response.headers["access-control-allow-origin"]
        == "https://localhost.tiangolo.com"
    )

  /** The HTTP {@code Access-Control-Allow-Headers} header field name. */
  public static final String ACCESS_CONTROL_ALLOW_HEADERS = "Access-Control-Allow-Headers";

  /** The HTTP {@code Access-Control-Allow-Methods} header field name. */
  public static final String ACCESS_CONTROL_ALLOW_METHODS = "Access-Control-Allow-Methods";

  /** The HTTP {@code Access-Control-Allow-Origin} header field name. */

    )
  }

  /**
   * Process the next protocol frame.
   *
   *  * If it is a control frame this will result in a single call to [FrameCallback].
   *  * If it is a message frame this will result in a single call to [FrameCallback.onReadMessage].
   *    If the message spans multiple frames, each interleaved control frame will result in a
   *    corresponding call to [FrameCallback].
   */
  @Throws(IOException::class)