![Events Diagram](../assets/images/******@****.***)

Here’s a [sample event listener](https://github.com/square/okhttp/blob/master/samples/guide/src/main/java/okhttp3/recipes/PrintEventsNonConcurrent.java) that prints each event with a timestamp.

```java
class PrintingEventListener extends EventListener {
  private long callStartNanos;

import okhttp3.survey.types.SuiteId

/**
 * Organizes information on SSL cipher suite inclusion and precedence for this spreadsheet.
 * https://docs.google.com/spreadsheets/d/1C3FdZSlCBq_-qrVwG1KDIzNIB3Hyg_rKAcgmSzOsHyQ/edit#gid=0
 */
class CipherSuiteSurvey(
  val clients: List<Client>,
  val ianaSuites: IanaSuites,
  val orderBy: List<SuiteId>,
) {
  fun printGoogleSheet() {
    print("name")
    for (client in clients) {

## Version 4.0.0

_2019-06-26_

**This release upgrades OkHttp to Kotlin.** We tried our best to make fast and safe to upgrade
from OkHttp 3.x. We wrote an [upgrade guide][upgrading_to_okhttp_4] to help with the migration and a
[blog post][okhttp4_blog_post] to explain it.

 *  Fix: Target Java 8 bytecode for Java and Kotlin.


## Version 4.0.0-RC3

_2019-06-24_

import java.security.interfaces.ECPublicKey
import java.security.interfaces.RSAPrivateKey
import java.security.interfaces.RSAPublicKey
import java.security.spec.PKCS8EncodedKeySpec
import java.util.UUID
import java.util.concurrent.TimeUnit
import okhttp3.internal.canParseAsIpAddress
import okhttp3.tls.internal.der.AlgorithmIdentifier
import okhttp3.tls.internal.der.AttributeTypeAndValue

private val prefix = if (File("samples").exists()) "" else "../../"

private fun mainFiles(): List<File> {
  val directories =
    listOf(
      "$prefix/samples/guide/src/main/java/okhttp3/guide",
      "$prefix/samples/guide/src/main/java/okhttp3/recipes",
      "$prefix/samples/guide/src/main/java/okhttp3/recipes/kt",
    ).map { File(it) }

  return directories.flatMap {
    it.listFiles().orEmpty().filter { f -> f.isFile }.toList()
  }
}

 [changelog]: https://square.github.io/okhttp/changelog/
 [conscrypt]: https://github.com/google/conscrypt/
 [get_example]: https://raw.github.com/square/okhttp/master/samples/guide/src/main/java/okhttp3/guide/GetExample.java
 [kotlin]: https://kotlinlang.org/
 [okhttp3_pro]: https://raw.githubusercontent.com/square/okhttp/master/okhttp/src/main/resources/META-INF/proguard/okhttp3.pro

include(":okhttp-logging-interceptor")
include(":okhttp-sse")
include(":okhttp-testing-support")
include(":okhttp-tls")
include(":okhttp-urlconnection")
include(":samples:compare")
include(":samples:crawler")
include(":samples:guide")
include(":samples:simple-client")
include(":samples:slack")
include(":samples:static-server")
include(":samples:tlssurvey")
include(":samples:unixdomainsockets")
include(":container-tests")

 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package okhttp3

import java.io.IOException
import java.util.UUID
import okhttp3.MediaType.Companion.toMediaType
import okhttp3.internal.toImmutableList
import okio.Buffer
import okio.BufferedSink
import okio.ByteString
import okio.ByteString.Companion.encodeUtf8

/**

    val uuidTag1 = UUID.randomUUID()
    val uuidTag2 = UUID.randomUUID()
    val request =
      Request.Builder()
        .url("https://square.com")
        .tag(UUID::class.java, uuidTag1)
        .tag(UUID::class.java, uuidTag2)
        .build()
    assertThat(request.tag(UUID::class.java)).isSameAs(uuidTag2)
  }

  @Test
  fun multipleTags() {
    val uuidTag = UUID.randomUUID()

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package okhttp3.guide;

import java.io.IOException;
import okhttp3.MediaType;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.RequestBody;
import okhttp3.Response;

public class PostExample {