return EventSource.Factory { request, listener ->
      val actualRequest =
        if (request.header("Accept") == null) {
          request.newBuilder().addHeader("Accept", "text/event-stream").build()
        } else {
          request
        }

      RealEventSource(actualRequest, listener).apply {
        connect(callFactory)
      }
    }
  }

  @JvmStatic

     * asynchronous process to connect the socket. Once that succeeds or fails, `listener` will be
     * notified. The caller must cancel the returned event source when it is no longer in use.
     */
    fun newEventSource(
      request: Request,
      listener: EventSourceListener,
    ): EventSource
  }

![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 {

  @RegisterExtension
  @JvmField
  var clientTestRule = OkHttpClientTestRule()

  private val listener = RecordingEventListener()
  private val handshakeCertificates = platform.localhostHandshakeCertificates()

  private var client =
    clientTestRule.newClientBuilder()
      .eventListenerFactory(clientTestRule.wrap(listener))
      .build()

  private lateinit var server: MockWebServer

  @BeforeEach

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

import okio.IOException

/**
 * Listener for connection events. Extend this class to monitor the new connections and closes.
 *
 * All event methods must execute fast, without external locking, cannot throw exceptions,

    val request =
      Request.Builder()
        .url(server.url("/"))
        .build()
    val response = client.newCall(request).execute()
    processResponse(response, listener)
    listener.assertOpen()
    listener.assertEvent(null, null, "hey")
    listener.assertClose()
  }

  @Test
  fun cancelShortCircuits() {
    server.enqueue(
      MockResponse.Builder()
        .body(
          """
          |data: hey

  private val name: String,
) : WebSocketListener() {
  private val events = LinkedBlockingQueue<Any>()
  private var delegate: WebSocketListener? = null

  /** Sets a delegate for handling the next callback to this listener. Cleared after invoked.  */
  fun setNextEventDelegate(delegate: WebSocketListener?) {
    this.delegate = delegate
  }

  override fun onOpen(
    webSocket: WebSocket,
    response: Response,
  ) {

    val response = call.execute()
    assertThat(response.code).isEqualTo(200)
    response.body.close()
    listener.removeUpToEvent(ConnectionEvent.ConnectEnd::class.java)
    listener.removeUpToEvent(ConnectionEvent.ConnectionReleased::class.java)
    listener.removeUpToEvent(ConnectionEvent.ConnectionAcquired::class.java)
    listener.removeUpToEvent(ConnectionEvent.ConnectionReleased::class.java)
  }

  @Test

    return delegate!!.session
  }

  override fun addHandshakeCompletedListener(listener: HandshakeCompletedListener) {
    delegate!!.addHandshakeCompletedListener(listener)
  }

  override fun removeHandshakeCompletedListener(listener: HandshakeCompletedListener) {
    delegate!!.removeHandshakeCompletedListener(listener)
  }

  @Throws(IOException::class)
  override fun startHandshake() {

   */
  open fun onClosed(
    webSocket: WebSocket,
    code: Int,
    reason: String,
  ) {
  }

  /**
   * Invoked when a web socket has been closed due to an error reading from or writing to the
   * network. Both outgoing and incoming messages may have been lost. No further calls to this
   * listener will be made.
   */
  open fun onFailure(