![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;

## 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_

 * 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 {

[Twitter][twitter_coc], [Ubuntu][ubuntu_coc], [GDC][gdc_coc], and [Django][django_coc] communities.
We are thankful for their work.

Reporting Guide
---------------

If you experience or witness unacceptable behavior — or have any other concerns — please report it by
emailing [******@****.***][codeofconduct_at]. All reports will be handled with
discretion.

 [jetty_8_252]: https://webtide.com/jetty-alpn-java-8u252/
 [junit_5_rules]: https://junit.org/junit5/docs/current/user-guide/#migrating-from-junit4-rulesupport
 [major_versions]: https://jakewharton.com/java-interoperability-policy-for-major-version-updates/
 [maven_provided]: https://maven.apache.org/guides/introduction/introduction-to-dependency-mechanism.html

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")

      }
    ```

 [CustomTrustJava]: https://github.com/square/okhttp/blob/master/samples/guide/src/main/java/okhttp3/recipes/CustomTrust.java
 [CustomTrustKotlin]: https://github.com/square/okhttp/blob/master/samples/guide/src/main/java/okhttp3/recipes/kt/CustomTrust.kt
 [CertificatePinningJava]: https://github.com/square/okhttp/blob/master/samples/guide/src/main/java/okhttp3/recipes/CertificatePinning.java

 * 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.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

public class GetExample {
  final OkHttpClient client = new OkHttpClient();