return EventListener.NONE;
      }
    }
  };

  ...
}
```

### Events with Failures

When an operation fails, a failure method is called. This is `connectFailed()` for failures while building a connection to the server, and `callFailed()` when the HTTP call fails permanently. When a failure happens it is possible that a `start` event won’t have a corresponding `end` event.

interface Callback {
  /**
   * Called when the request could not be executed due to cancellation, a connectivity problem or
   * timeout. Because networks can fail during an exchange, it is possible that the remote server
   * accepted the request before the failure.
   */
  fun onFailure(
    call: Call,
    e: IOException,
  )

  /**

   * processing an event.
   *
   * @return false when EOF is reached
   */
  @Throws(IOException::class)
  fun processNextEvent(): Boolean {
    var id = lastId
    var type: String? = null
    val data = Buffer()

    while (true) {
      when (source.select(options)) {
        in 0..2 -> {
          completeEvent(id, type, data)
          return true

      logger.log(requestStartMessage)

      if (logHeaders) {
        val headers = request.headers

        if (requestBody != null) {
          // Request body headers are only present when installed as a network interceptor. When not
          // already present, force them to be included (if available) so their values are known.
          requestBody.contentType()?.let {
            if (headers["Content-Type"] == null) {

 * limitations under the License.
 */
package okhttp3.internal

import java.net.InetAddress
import okhttp3.Dns

/**
 * A network that always resolves two IP addresses per host. Use this when testing route selection
 * fallbacks to guarantee that a fallback address is available.
 */
class DoubleInetAddressDns : Dns {
  override fun lookup(hostname: String): List<InetAddress> {

     * 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
  }

  override fun isSupported(): Boolean = BouncyCastlePlatform.isSupported

  override fun getSelectedProtocol(sslSocket: SSLSocket): String? {
    val s = sslSocket as BCSSLSocket

    return when (val protocol = s.applicationProtocol) {
      null, "" -> null
      else -> protocol
    }
  }

  override fun configureTlsExtensions(
    sslSocket: SSLSocket,
    hostname: String?,

        val stories = HpackJsonUtil.readStories(interopTestName)
        result.addAll(stories)
      }
      return result
    }

    /**
     * Checks if `expected` and `observed` are equal when viewed as a set and headers are
     * deduped.
     *
     * TODO: See if duped headers should be preserved on decode and verify.
     */
    private fun assertSetEquals(
      message: String,

      .withNetwork(network)
      .withExposedPorts(1080)

  @Test
  fun testLocal() {
    MockServerClient(mockServer.host, mockServer.serverPort).use { mockServerClient ->
      mockServerClient
        .`when`(
          request().withPath("/person")
            .withQueryStringParameter("name", "peter"),
        )
        .respond(response().withBody("Peter the person!"))

      val client =
        OkHttpClient.Builder()

 * or response.
 *
 * Implementations of this interface throw [IOException] to signal connectivity failures. This
 * includes both natural exceptions such as unreachable servers, as well as synthetic exceptions
 * when responses are of an unexpected type or cannot be decoded.
 *
 * Other exception types cancel the current call:
 *
 *  * For synchronous calls made with [Call.execute], the exception is propagated to the caller.
 *