*  * Optional [CONNECT tunnels][connectTunnel]. When using an HTTP proxy to reach an HTTPS server
 *    we must send a `CONNECT` request, and handle authorization challenges from the proxy.
 *  * Optional [TLS handshake][connectTls].
 *
 * Each step may fail. If a retry is possible, a new instance is created with the next plan, which
 * will be configured differently.
 */
class ConnectPlan(
  private val taskRunner: TaskRunner,

   * @since 27.1
   */
  Set<E> edgesConnecting(EndpointPair<N> endpoints);

  /**
   * Returns the single edge that directly connects {@code nodeU} to {@code nodeV}, if one is
   * present, or {@code Optional.empty()} if no such edge exists.
   *
   * <p>In an undirected network, this is equal to {@code edgeConnecting(nodeV, nodeU)}.
   *

**OkHttp now supports Happy Eyeballs ([RFC 8305][rfc_8305]) for IPv4+IPv6 networks.** It attempts
both IPv6 and IPv4 connections concurrently, keeping whichever connects first.

**We’ve improved our Kotlin APIs.** You can skip the builder:

```kotlin
val request = Request(
  url = "https://cash.app/".toHttpUrl(),
)
```

**OkHttp now supports [GraalVM].**

 * `RESTRICTED_TLS` is a secure configuration, intended to meet stricter compliance requirements.
 * `MODERN_TLS` is a secure configuration that connects to modern HTTPS servers.
 * `COMPATIBLE_TLS` is a secure configuration that connects to secure–but not current–HTTPS servers.
 * `CLEARTEXT` is an insecure configuration that is used for `http://` URLs.

    calls that use a pooled connection.


## Version 4.3.1

_2020-01-07_

 *  Fix: Don't crash with a `NullPointerException` when a web socket is closed before it connects.
    This regression was introduced in OkHttp 4.3.0.
 *  Fix: Don't crash with an `IllegalArgumentException` when using custom trust managers on

        if (headerList == null) {
            headerList = new ArrayList<>();
        }
        headerList.add(new String[] { key, value });
        return this;
    }

    /**
     * Connects to the URL and executes the request.
     *
     * @param actionListener the action listener for handling the response
     * @param exceptionListener the exception listener for handling exceptions
     */

   *
   * This test yields threads to force the decision of plan1 to be deliberate and not lucky. In
   * particular, we set up this sequence of events:
   *
   *  1. take plan 0
   *  3. plan 0 connects
   *  4. finish taking plan 1
   *
   * https://github.com/square/okhttp/issues/7152
   */
  @Test
  fun reusePlanAndNewConnectRace() {
    val plan0 = routePlanner.addPlan()