* custom builds of OkHttp please include a qualifier your version name, like "4.7.0-mycompany.3".
   * The version string is configured in the root project's `build.gradle`.
   *
   * Note that OkHttp's runtime version may be different from the version specified in your
   * project's build file due to the dependency resolution features of your build tool.
   *
   * [semver]: https://semver.org
   */

/**
 * A domain name service that resolves IP addresses for host names. Most applications will use the
 * [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 {
  /**

    assertThat(response.isSuccessful).isTrue()

    val recordedRequest = server.takeRequest()
    assertThat(recordedRequest.handshakeServerNames).containsExactly(url.host)
  }

  /**
   * Use different hostnames for the TLS handshake (including SNI) and the HTTP request (in the
   * Host header).
   */
  @Test
  fun domainFronting() {
    val heldCertificate =
      HeldCertificate.Builder()

          file = null
        }
      }

      fileToClose?.closeQuietly()
    }
  }

  companion object {
    // TODO(jwilson): what to do about timeouts? They could be different and unfortunately when any
    //     timeout is hit we like to tear down the whole stream.

    private const val SOURCE_UPSTREAM = 1
    private const val SOURCE_FILE = 2

      |
      """.trimMargin()
    val heldCertificate = decode(certificatePem + pkcs8Pem)
    assertThat(heldCertificate.certificatePem()).isEqualTo(certificatePem)

    // Slightly different encoding
    if (platform.isBouncyCastle()) {
      assertThat(heldCertificate.privateKeyPkcs8Pem()).isEqualTo(bcPkcs8Pem)
    } else {
      assertThat(heldCertificate.privateKeyPkcs8Pem()).isEqualTo(pkcs8Pem)
    }

    This particularly-subtle bug was caused by us assigning each `OkHttpClient` instance its own
    `NullProxySelector` when an explicit proxy is configured. But we don't share connections when
    the proxy selectors are different. Ugh!


## Version 4.2.0

_2019-09-10_

 *  New: API to decode a certificate and private key to create a `HeldCertificate`. This accepts a

import okhttp3.internal.platform.Platform

/**
 * Example of using a hardware key to perform client auth.
 * Prefer recent JDK builds, and results are temperamental to slight environment changes.
 * Different instructions and configuration may be required for other hardware devices.
 *
 * Using a yubikey device as a SSL key store.
 * https://lauri.võsandi.com/2017/03/yubikey-for-ssh-auth.html
 *

   * Content-Type: text/html
   * Content-Length: 50
   * ```
   *
   * 2. Different order
   *
   * ```
   * Content-Length: 50
   * Content-Type: text/html
   * ```
   *
   * 3. Different case
   *
   * ```
   * content-type: text/html
   * content-length: 50
   * ```
   *
   * 4. Different values
   *
   * ```
   * Content-Type: text/html
   * Content-Length: 050

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

  /** Returns the connection to use, which might be different from [connection]. */
  override fun handleSuccess(): RealConnection {
    user.updateRouteDatabaseAfterSuccess(route)

    val connection = this.connection!!
    user.connectionConnectEnd(connection, route)

    // If we raced another call connecting to this host, coalesce the connections. This makes for
    // 3 different lookups in the connection pool!