}
            // Add brackets for IPv6
            return "[" + address + "]";
        }
        return address;
    }

    /**
     * Compresses an IPv6 address string to its canonical compressed form.
     * For example, "0:0:0:0:0:0:0:1" becomes "::1"
     *
     * @param ipv6Address the IPv6 address string to compress
     * @return the compressed IPv6 address string
     */

    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

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

     */
    @Override
    public InetAddress[] resolve(final String host) throws UnknownHostException {
        // Handle IPv6 addresses in bracket notation
        if (host != null && host.length() > 2 && host.startsWith("[") && host.endsWith("]")) {
            // Remove brackets for IPv6 address resolution
            final String ipv6Address = host.substring(1, host.length() - 1);

        IdnDnsResolver resolver = new IdnDnsResolver();

        // Test IPv6 loopback address with brackets
        String host = "[::1]";
        InetAddress[] addresses = resolver.resolve(host);
        assertNotNull(addresses);
        assertTrue(addresses.length > 0);
        // IPv6 loopback can be represented as ::1 or 0:0:0:0:0:0:0:1
        String hostAddress = addresses[0].getHostAddress();

        .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());

        .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.

          }

          call.eventListener.dnsEnd(call, socketHost, result)
          result
        }

      // Try each address for best behavior in mixed IPv4/IPv6 environments.
      val orderedAddresses =
        when {
          fastFallback -> reorderForHappyEyeballs(addresses)
          else -> addresses
        }

      for (inetAddress in orderedAddresses) {

OkHttp perseveres when the network is troublesome: it will silently recover from common connection
problems. If your service has multiple IP addresses, OkHttp will attempt alternate addresses if the
first connect fails. This is necessary for IPv4+IPv6 and services hosted in redundant data
centers. OkHttp supports modern TLS features (TLS 1.3, ALPN, certificate pinning). It can be
configured to fall back for broad connectivity.