By default, OkHttp will attempt a `MODERN_TLS` connection.  However by configuring the client connectionSpecs you can allow a fall back to `COMPATIBLE_TLS` connection if the modern configuration fails.

```java
OkHttpClient client = new OkHttpClient.Builder()
    .connectionSpecs(Arrays.asList(ConnectionSpec.MODERN_TLS, ConnectionSpec.COMPATIBLE_TLS))
    .build();
```

    The best practice in OkHttp 3 is to create a single OkHttpClient instance
    and share it throughout the application. Requests that needs a customized
    client should call `OkHttpClient.newBuilder()` on that shared instance.
    This allows customization without the drawbacks of separate connection
    pools.

 *  **OkHttpClient is now stateless.** In the 2.x API `OkHttpClient` had getters

 * limitations under the License.
 */
package okhttp3.recipes.kt

import java.io.IOException
import java.security.cert.X509Certificate
import okhttp3.OkHttpClient
import okhttp3.Request.Builder
import okhttp3.tls.HandshakeCertificates
import okhttp3.tls.decodeCertificatePem

class CustomTrust {

 *
 *
 * The resulting file is used by [PublicSuffixDatabase].
 */
class PublicSuffixListGenerator(
  projectRoot: Path = ".".toPath(),
  val fileSystem: FileSystem = FileSystem.SYSTEM,
  val client: OkHttpClient = OkHttpClient(),
) {
  private val resources = projectRoot / "okhttp/src/main/resources/okhttp3/internal/publicsuffix"
  private val testResources = projectRoot / "okhttp/src/test/resources/okhttp3/internal/publicsuffix"

   */
  @Throws(IOException::class)
  fun execute(): Response

  /**
   * Schedules the request to be executed at some point in the future.
   *
   * The [dispatcher][OkHttpClient.dispatcher] defines when the request will run: usually
   * immediately unless there are several other requests currently being executed.
   *

import javax.net.ssl.SSLSocketFactory
import okhttp3.Call
import okhttp3.Connection
import okhttp3.ConnectionSpec
import okhttp3.DelegatingSSLSocketFactory
import okhttp3.EventListener
import okhttp3.OkHttpClient
import okhttp3.Request
import org.junit.jupiter.api.Tag
import org.junit.jupiter.api.Test

/**
 * Tests for ALPN overriding on Android.
 */
@Tag("Remote")
class AlpnOverrideTest {

      builder.eventListenerFactory(LoggingEventListener.Factory(logger))
    }
    return builder.build()
  }

  fun close() {
    val okHttpClient = client as OkHttpClient
    okHttpClient.connectionPool.evictAll() // Close any persistent connections.
    okHttpClient.dispatcher.executorService.shutdownNow()
  }

  companion object {
    internal const val NAME = "okcurl"
    internal const val DEFAULT_TIMEOUT = -1

import assertk.assertThat
import assertk.assertions.contains
import java.net.InetSocketAddress
import java.net.Proxy
import java.net.Proxy.Type.SOCKS
import okhttp3.HttpUrl.Companion.toHttpUrl
import okhttp3.OkHttpClient
import okhttp3.Request
import okhttp3.containers.BasicMockServerTest.Companion.MOCKSERVER_IMAGE
import org.junit.jupiter.api.Test
import org.mockserver.client.MockServerClient

package okhttp3.recipes;

import java.io.IOException;
import java.security.cert.Certificate;
import okhttp3.CertificatePinner;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

public final class CertificatePinning {
  private final OkHttpClient client = new OkHttpClient.Builder()
      .certificatePinner(
          new CertificatePinner.Builder()

import okhttp3.CacheControl
import okhttp3.Call
import okhttp3.Callback
import okhttp3.Dns
import okhttp3.HttpUrl
import okhttp3.MediaType
import okhttp3.MediaType.Companion.toMediaType
import okhttp3.OkHttpClient
import okhttp3.Protocol
import okhttp3.Request
import okhttp3.RequestBody.Companion.toRequestBody
import okhttp3.Response
import okhttp3.internal.platform.Platform