val referer: String? by option("-e", "--referer", help = "Referer URL")

  val verbose: Boolean by option("-v", "--verbose", help = "Makes $NAME verbose during the operation").flag()

  val sslDebug: Boolean by option(help = "Output SSL Debug").flag()

  val url: String? by argument(name = "url", help = "Remote resource URL")

  var client: Call.Factory? = null

        return new MetricsEventListener(call);
      } else {
        return EventListener.NONE;
      }
    }
  };

  ...
}
```

### Events with Failures

  override fun checkClientTrusted(
    chain: Array<out X509Certificate>,
    authType: String?,
  ) = throw CertificateException("Unsupported operation")

  override fun checkServerTrusted(
    chain: Array<out X509Certificate>,
    authType: String,
  ) = throw CertificateException("Unsupported operation")

  ) = throw CertificateException("Unsupported operation")

  override fun checkClientTrusted(
    chain: Array<out X509Certificate>,
    authType: String?,
  ) = throw CertificateException("Unsupported operation")

  override fun checkClientTrusted(
    chain: Array<out X509Certificate>,
    authType: String,
    engine: SSLEngine?,
  ) = throw CertificateException("Unsupported operation")

  override fun checkClientTrusted(

   */
  @Throws(UnknownHostException::class)
  fun lookup(hostname: String): List<InetAddress>

  companion object {
    /**
     * A DNS that uses [InetAddress.getAllByName] to ask the underlying operating system to
     * lookup IP addresses. Most custom [Dns] implementations should delegate to this instance.
     */
    @JvmField
    val SYSTEM: Dns = DnsSystem()

    private class DnsSystem : Dns {

      exactRuleLabels
    } else {
      wildcardRuleLabels
    }
  }

  /**
   * Reads the public suffix list treating the operation as uninterruptible. We always want to read
   * the list otherwise we'll be left in a bad state. If the thread was interrupted prior to this
   * operation, it will be re-interrupted after the list is read.
   */
  private fun readTheListUninterruptibly() {
    var interrupted = false
    try {

    or newer.

    ```kotlin
    implementation("com.squareup.okio:okio:1.17.3")
    ```

 *  Fix: Don't miss cancels when sending HTTP/2 request headers.
 *  Fix: Don't miss whole operation timeouts when calls redirect.
 *  Fix: Don't leak connections if web sockets have malformed responses or if `onOpen()` throws.
 *  Fix: Don't retry when request bodies fail due to `FileNotFoundException`.

   * canceled. For example, happy-path events like [requestHeadersStart] and [requestHeadersEnd] may
   * occur after a call is canceled. Typically cancellation takes effect when an expensive I/O
   * operation is required.
   *
   * This is invoked at most once, even if [Call.cancel] is invoked multiple times. It may be
   * invoked at any point in a call's life, including before [callStart] and after [callEnd].
   */

  // performed while holding this lock!
  //
  // Socket writes are guarded by frameWriter.
  //
  // Socket reads are unguarded but are only made by the reader thread.
  //
  // Certain operations (like SYN_STREAM) need to synchronize on both the frameWriter (to do
  // blocking I/O) and this (to create streams). Such operations must synchronize on 'this' last.

This lock guards internal state of each connection. This lock is never held for blocking operations. That means that we acquire the lock, read or write a few fields and release the lock. No I/O and no application-layer callbacks.

#### Http2Stream