*   <dt>An IPv6 "IPv4 mapped" address, {@code "::ffff:192.168.0.1"}.
 *   <dd>{@code 00 00 00 00 00 00 00 00 00 00 ff ff c0 a8 00 01}
 * </dl>
 *
 * <p>A few notes about IPv6 "IPv4 mapped" addresses and their observed use in Java.
 *
 * <p>"IPv4 mapped" addresses were originally a representation of IPv4 addresses for use on an IPv6
 * socket that could receive both IPv4 and IPv6 connections (by disabling the {@code IPV6_V6ONLY}

    val request = Request(server1.url("/"))

    server1.enqueue(refusedStream)
    server2.enqueue(bodyResponse)

    dns[server1.hostName] = listOf(ipv6, ipv4)
    socketFactory[ipv6] = server1.socketAddress
    socketFactory[ipv4] = server2.socketAddress

    client =
      client
        .newBuilder()
        .fastFallback(false)
        .apply {
          retryOnConnectionFailure = false

 *   <dt>An IPv6 "IPv4 mapped" address, {@code "::ffff:192.168.0.1"}.
 *   <dd>{@code 00 00 00 00 00 00 00 00 00 00 ff ff c0 a8 00 01}
 * </dl>
 *
 * <p>A few notes about IPv6 "IPv4 mapped" addresses and their observed use in Java.
 *
 * <p>"IPv4 mapped" addresses were originally a representation of IPv4 addresses for use on an IPv6
 * socket that could receive both IPv4 and IPv6 connections (by disabling the {@code IPV6_V6ONLY}

import org.junitpioneer.jupiter.RetryingTest
import org.opentest4j.TestAbortedException

/**
 * This test binds two different web servers (IPv4 and IPv6) to the same port, but on different
 * local IP addresses. Requests made to `127.0.0.1` will reach the IPv4 server, and requests made to
 * `::1` will reach the IPv6 server.
 *
 * By orchestrating two different servers with the same port but different IP addresses, we can

    }
  }
  return result.readUtf8()
}

/**
 * Returns the canonical address for [address]. If [address] is an IPv6 address that is mapped to an
 * IPv4 address, this returns the IPv4-mapped address. Otherwise, this returns [address].
 *
 * https://en.wikipedia.org/wiki/IPv6#IPv4-mapped_IPv6_addresses
 */
internal fun canonicalizeInetAddress(address: ByteArray): ByteArray =
  when {

        .testEquals();
  }

  public void testRequireBracketsForIPv6() {
    // Bracketed IPv6 works fine.
    assertEquals("::1", HostAndPort.fromString("[::1]").requireBracketsForIPv6().getHost());
    assertEquals("::1", HostAndPort.fromString("[::1]:80").requireBracketsForIPv6().getHost());
    // Non-bracketed non-IPv6 works fine.
    assertEquals("x", HostAndPort.fromString("x").requireBracketsForIPv6().getHost());

_2022-02-01_

**This release introduces fast fallback to better support mixed IPv4+IPv6 networks.** Fast fallback
is what we're calling our implementation of Happy Eyeballs, [RFC 8305][rfc_8305]. With this
feature OkHttp will attempt both IPv6 and IPv4 connections concurrently, keeping whichever connects
first. Fast fallback gives IPv6 connections a 250 ms head start so IPv6 is preferred on networks
where it's available.

http://%zz%66%a.com

# If we get an invalid character that has been escaped.
http://%25
http://hello%00

# Escaped numbers should be treated like IP addresses if they are.
# No special handling for IPv4 or IPv4-like URLs
http://%30%78%63%30%2e%30%32%35%30.01  s:http p:/ h:192.168.0.1
http://%30%78%63%30%2e%30%32%35%30.01%2e  s:http p:/ h:0xc0.0250.01.
http://192.168.0.257

    assertThat(localVerifier.verify("\uD83D\uDCA9.com", session)).isFalse()
  }

  @Test fun verifyAsIpAddress() {
    // IPv4
    assertThat("127.0.0.1".canParseAsIpAddress()).isTrue()
    assertThat("1.2.3.4".canParseAsIpAddress()).isTrue()

    // IPv6
    assertThat("::1".canParseAsIpAddress()).isTrue()
    assertThat("2001:db8::1".canParseAsIpAddress()).isTrue()

 *  Fix: Recover gracefully when a coalesced connection immediately goes unhealthy.
 *  Fix: Defer the `SecurityException` when looking up the default proxy selector.
 *  Fix: Don't use brackets formatting IPv6 host names in MockWebServer.
 *  Fix: Don't permit cache iterators to remove entries that are being written.


## Version 4.0.1

_2019-07-10_