* [system DNS service][SYSTEM], which is the default. Some applications may provide their own
 * implementation to use a different DNS server, to prefer IPv6 addresses, to prefer IPv4 addresses,
 * or to force a specific known IP address.
 *
 * Implementations of this interface must be safe for concurrent use.
 */
fun interface Dns {
  /**

    // Write metadata to the end of the file.
    writeMetadata(upstreamSize)
    file!!.channel.force(false)

    // Once everything else is in place we can swap the dirty header for a clean one.
    writeHeader(PREFIX_CLEAN, upstreamSize, metadata.size.toLong())
    file!!.channel.force(false)

    // This file is complete.
    synchronized(this@Relay) {
      complete = true
    }

        val headers = request.headers

        if (requestBody != null) {
          // Request body headers are only present when installed as a network interceptor. When not
          // already present, force them to be included (if available) so their values are known.
          requestBody.contentType()?.let {
            if (headers["Content-Type"] == null) {
              logger.log("Content-Type: $it")
            }

      if (i == 2) {
        // Force this request's response to be written to the cache. This way, subsequent responses
        // can be read from the cache.
        System.out.println("Force cache: true");
        clientForCall = client.newBuilder()
            .addNetworkInterceptor(REWRITE_CACHE_CONTROL_INTERCEPTOR)
            .build();
      } else {
        System.out.println("Force cache: false");
        clientForCall = client;

      }
    assertThat(requestsMade.size).isEqualTo(0)
    mockWebServer.dispatcher = dispatcher
    val url = mockWebServer.url("/").toUrl()
    val conn = url.openConnection() as HttpURLConnection
    conn.responseCode // Force the connection to hit the "server".
    // Make sure our dispatcher got the request.
    assertThat(requestsMade.size).isEqualTo(1)
  }

  @Test
  fun outOfOrderResponses() {
    val firstResponseCode = AtomicInteger()

1. Add an Emulator named `pixel5`, if you don't already have one

```
$ sdkmanager --install "system-images;android-29;google_apis;x86"
$ echo "no" | avdmanager --verbose create avd --force --name "pixel5" --device "pixel" --package "system-images;android-29;google_apis;x86" --tag "google_apis" --abi "x86"
```

2. Run an Emulator using Android Studio or from command line.

```

    client.newCall(request).execute().use { response ->
      assertEquals(200, response.code)
    }

    client.connectionPool.evictAll()
    assertEquals(0, client.connectionPool.connectionCount())

    // Force reuse. This appears flaky (30% of the time) even though sessions are reused.
    // javax.net.ssl.SSLHandshakeException: No new session is allowed and no existing
    // session can be resumed
    //

=== ":material-language-kotlin: Kotlin"
    ```kotlin
      private val client: OkHttpClient = OkHttpClient.Builder()

  /**
   * Sends a reply to an incoming stream.
   *
   * @param outFinished true to eagerly finish the output stream to send data to the remote peer.
   *     Corresponds to `FLAG_FIN`.
   * @param flushHeaders true to force flush the response headers. This should be true unless the
   *     response body exists and will be written immediately.
   */
  @Throws(IOException::class)
  fun writeHeaders(
    responseHeaders: List<Header>,

 * doesn't cache partial responses.
 *
 * ## Force a Network Response
 *
 * In some situations, such as after a user clicks a 'refresh' button, it may be necessary to skip
 * the cache, and fetch data directly from the server. To force a full refresh, add the `no-cache`
 * directive:
 *
 * ```java
 * Request request = new Request.Builder()