///

### DNS { #dns }

Şimdi gerçek HTTPS parçalarına odaklanalım.

Önce tarayıcı, bu örnekte `someapp.example.com` olan domain için **IP**’nin ne olduğunu **DNS server**’larına sorar.

DNS server’ları tarayıcıya belirli bir **IP adresini** kullanmasını söyler. Bu, DNS server’larında yapılandırdığınız ve server’ınızın kullandığı public IP adresidir.

package okhttp3.internal

import java.net.InetAddress
import okhttp3.Dns

/**
 * A network that always resolves two IP addresses per host. Use this when testing route selection
 * fallbacks to guarantee that a fallback address is available.
 */
class DoubleInetAddressDns : Dns {
  override fun lookup(hostname: String): List<InetAddress> {
    val addresses = Dns.SYSTEM.lookup(hostname)
    return listOf(addresses[0], addresses[0])
  }

      }

    /**
     * Sets the DNS service used to lookup IP addresses for hostnames.
     *
     * If unset, the [system-wide default][Dns.SYSTEM] DNS will be used.
     */
    fun dns(dns: Dns) =
      apply {
        if (dns != this.dns) {
          this.routeDatabase = null
        }
        this.dns = dns
      }

    /**

    val followRedirects: Boolean

    /**
     * Get the [DNS] instance for the OkHttpClient, or an override from the Call.Chain.
     */
    val dns: Dns

    /**
     * Override the [DNS] for the Call.Chain.
     *
     * @throws IllegalStateException if this is a Network Interceptor, since the override is too late.
     */
    fun withDns(dns: Dns): Chain

    /**

        override fun peek(): MockResponse = TODO()

        override fun shutdown() = TODO()
      }
  }

  @Test
  fun dns() {
    var dns: Dns = Dns { TODO() }

    val system: Dns = Dns.SYSTEM
  }

  @Test
  fun eventListener() {
    val eventListener =
      object : EventListener() {
        override fun callStart(call: Call) = TODO()

///

### DNS { #dns }

Now let's focus on all the actual HTTPS parts.

First, the browser would check with the **DNS servers** what is the **IP for the domain**, in this case, `someapp.example.com`.

The DNS servers would tell the browser to use some specific **IP address**. That would be the public IP address used by your server, that you configured in the DNS servers.

#### DNS SRV Records

Kotlin calling OkHttp 3.x:

```kotlin
val client = OkHttpClient.Builder()
    .dns { hostname -> InetAddress.getAllByName(hostname).toList() }
    .build()
```

Kotlin calling OkHttp 4.x:

```kotlin
val client = OkHttpClient.Builder()
    .dns(object : Dns {
      override fun lookup(hostname: String) =
          InetAddress.getAllByName(hostname).toList()
    })

///

### DNS { #dns }

Agora vamos focar em todas as partes que realmente fazem parte do HTTPS.

Primeiro, o navegador iria verificar com os servidores DNS qual o IP do domínio, nesse caso, `someapp.example.com`.

 *     a race in fast follow-up.
 *
 *  4. If there's no existing connection, make a list of routes (which may require blocking DNS
 *     lookups) and attempt new connections to them. When failures occur, retries iterate the
 *     list of available routes.
 *
 * If the pool gains an eligible connection while DNS, TCP, or TLS work is in flight, this finder
 * will prefer pooled connections. Only pooled HTTP/2 connections are used for such de-duplication.