eventClass: Class<out ConnectionEvent>? = null,
    elapsedMs: Long = -1L,
  ): ConnectionEvent {
    val result = eventSequence.remove()
    val actualElapsedNs = result.timestampNs - (lastTimestampNs ?: result.timestampNs)
    lastTimestampNs = result.timestampNs

    if (eventClass != null) {
      assertThat(result).isInstanceOf(eventClass)
    }

    if (elapsedMs != -1L) {
      assertThat(

![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;

  private void printEvent(String name) {
    long nowNanos = System.nanoTime();
    if (name.equals("callStart")) {

   */
  internal var allocationLimit = 1
    private set

  /** Current calls carried by this connection. */
  val calls = mutableListOf<Reference<RealCall>>()

  /** Timestamp when `allocations.size()` reached zero. Also assigned upon initial connection. */
  var idleAtNs = Long.MAX_VALUE

  /**
   * Returns true if this is an HTTP/2 connection. Such connections can be used in multiple HTTP

    eventClass: Class<out CallEvent>? = null,
    elapsedMs: Long = -1L,
  ): CallEvent {
    val result = eventSequence.remove()
    val actualElapsedNs = result.timestampNs - (lastTimestampNs ?: result.timestampNs)
    lastTimestampNs = result.timestampNs

    if (eventClass != null) {
      assertThat(result).isInstanceOf(eventClass)
    }

    if (elapsedMs != -1L) {
      assertThat(

          override fun encode(
            writer: DerWriter,
            value: String,
          ) = writer.writeUtf8(value)
        },
    )

  /**
   * A timestamp like "191216030210Z" or "191215190210-0800" for 2019-12-15T19:02:10-08:00. The
   * cutoff of the 2-digit year is 1950-01-01T00:00:00Z.
   */
  val UTC_TIME =
    BasicDerAdapter(
      name = "UTC TIME",

     */
    private var expires: Date? = null

    /**
     * Extension header set by OkHttp specifying the timestamp when the cached HTTP request was
     * first initiated.
     */
    private var sentRequestMillis = 0L

    /**
     * Extension header set by OkHttp specifying the timestamp when the cached HTTP response was
     * first received.
     */
    private var receivedResponseMillis = 0L

  runtimeClasspath {
    /*
       - The below two ignored files are generated during test execution
       by the test: okhttp/src/test/java/okhttp3/osgi/OsgiTest.java

       - The compressed index.xml file contains a timestamp property which
       changes with every test execution, such that running the test
       actually changes the test classpath itself. This means that it
       can"t benefit from incremental build acceleration, because on every

  /**
   * Returns a [timestamp][System.currentTimeMillis] taken immediately before OkHttp
   * transmitted the initiating request over the network. If this response is being served from the
   * cache then this is the timestamp of the original request.
   */
  @get:JvmName("sentRequestAtMillis") val sentRequestAtMillis: Long,
  /**
   * Returns a [timestamp][System.currentTimeMillis] taken immediately after OkHttp

 *  Fix: Prefer the server's response body on all conditional cache misses. Previously we would
    return the cached response's body if it had a newer `Last-Modified` date.
 *  Fix: Update the stored timestamp on conditional cache hits.
 *  New: Optimized HTTP/2 request header encoding. More headers are HPACK-encoded and string
    literals are now Huffman-encoded.
 *  New: Expose `Part` headers and body in `Multipart`.

  }

  data class ConnectionClosed(
    override val timestampNs: Long,
    override val connection: Connection,
  ) : ConnectionEvent()

  data class ConnectionAcquired(
    override val timestampNs: Long,
    override val connection: Connection,
    val call: Call,
  ) : ConnectionEvent()

  data class ConnectionReleased(
    override val timestampNs: Long,
    override val connection: Connection,
    val call: Call,