*/
@Timeout(30)
class FastFallbackTest {
  @RegisterExtension
  val clientTestRule = OkHttpClientTestRule()

  // Don't use JUnit 5 test rules for these; otherwise we can't bind them to a single local IP.
  private lateinit var localhostIpv4: InetAddress
  private lateinit var localhostIpv6: InetAddress
  private lateinit var serverIpv4: MockWebServer
  private lateinit var serverIpv6: MockWebServer

    port: Int,
  ) = start(InetSocketAddress(inetAddress, port))

  /**
   * Starts the server and binds to the given socket address.
   *
   * @param inetSocketAddress the socket address to bind the server on
   */
  @Synchronized
  @Throws(IOException::class)
  private fun start(inetSocketAddress: InetSocketAddress) {
    check(!shutdown) { "shutdown() already called" }
    if (started) return

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