* HTTP request/response exchanges. Connections may be direct to the origin server or via a proxy.
 *
 * Typically instances of this class are created, connected and exercised automatically by the HTTP
 * client. Applications may use this class to monitor HTTP connections as members of a
 * [connection pool][ConnectionPool].
 *

     *   increase availability of multi-homed services.
     *
     * * **Stale pooled connections.** The [ConnectionPool] reuses sockets
     *   to decrease request latency, but these connections will occasionally time out.
     *
     * * **Unreachable proxy servers.** A [ProxySelector] can be used to

 *  Upgrade: [Kotlin 1.3.71][kotlin_1_3_71].


## Version 4.5.0

_2020-04-06_

**This release fixes a severe bug where OkHttp incorrectly detected and recovered from unhealthy
connections.** Stale or canceled connections were incorrectly attempted when they shouldn't have
been, leading to rare cases of infinite retries. Please upgrade to this release!

    be called.

    Web sockets have always been had pings, but pings on HTTP/2 connections is
    new in this release. Pings are used for connections that are busy carrying
    calls and for idle connections in the connection pool. (Pings do not impact
    when pooled connections are evicted).

    If you have a configured ping interval, you should confirm that it is long

  override fun createRequestBody(
    request: Request,
    contentLength: Long,
  ): Sink =
    when {
      request.body?.isDuplex() == true -> throw ProtocolException(
        "Duplex connections are not supported for HTTP/1",
      )
      request.isChunked -> newChunkedSink() // Stream a request body of unknown length.
      contentLength != -1L -> newKnownLengthSink() // Stream a request body of a known length.

import okhttp3.internal.toImmutableList

/**
 * A specification for a connection to an origin server. For simple connections, this is the
 * server's hostname and port. If an explicit proxy is requested (or [no proxy][Proxy.NO_PROXY] is
 * explicitly requested), this also includes that proxy information. For secure connections the
 * address also includes the SSL socket factory, hostname verifier, and certificate pinner.
 *

## Retrying Requests

Sometimes connections fail: either a pooled connection was stale and disconnected, or the webserver itself couldn’t be reached. OkHttp will retry the request with a different route if one is available.

  /** Returns the number of idle connections in the pool. */
  fun idleConnectionCount(): Int = delegate.idleConnectionCount()

  /** Returns total number of connections in the pool. */
  fun connectionCount(): Int = delegate.connectionCount()

  internal val connectionListener: ConnectionListener
    get() = delegate.connectionListener

  /** Close and remove all idle connections in the pool. */
  fun evictAll() {

import java.net.Proxy
import java.net.Socket
import okhttp3.Connection
import okhttp3.Handshake
import okhttp3.HttpUrl
import okhttp3.Protocol
import okhttp3.Route

/**
 * A user that is a connection pool creating connections in the background
 * without an intent to immediately use them.
 */
object PoolConnectionUser : ConnectionUser {
  override fun addPlanToCancel(connectPlan: ConnectPlan) {
  }

  /**
   * True if ALPN is used on incoming HTTPS connections to negotiate a protocol like HTTP/1.1 or
   * HTTP/2. This is true by default; set to false to disable negotiation and restrict connections
   * to HTTP/1.1.
   */
  public var protocolNegotiationEnabled: Boolean = true

  /**
   * The protocols supported by ALPN on incoming HTTPS connections in order of preference. The list