*/
interface Connection {
  /** Returns the route used by this connection. */
  fun route(): Route

  /**
   * Returns the socket that this connection is using. Returns an
   * [SSL socket][javax.net.ssl.SSLSocket] if this connection is HTTPS. If this is an HTTP/2
   * connection the socket may be shared by multiple concurrent calls.
   */
  fun socket(): Socket

 * When making TLS connections with multiple [connection specs](https://square.github.io/okhttp/4.x/okhttp/okhttp3/-connection-spec/), these are attempted in sequence until the TLS handshake succeeds.

### [Connections](https://square.github.io/okhttp/4.x/okhttp/okhttp3/-connection/)

When you request a URL with OkHttp, here's what it does:

 *
 *  4. If there's no existing connection, make a list of routes (which may require blocking DNS
 *     lookups) and attempt a new connection them. When failures occur, retries iterate the list of
 *     available routes.
 *
 * If the pool gains an eligible connection while DNS, TCP, or TLS work is in flight, this finder
 * will prefer pooled connections. Only pooled HTTP/2 connections are used for such de-duplication.
 *

    connection: Connection,
    route: Route,
    call: Call,
  ) {}

  /**
   * Invoked when a connection is released as no longer required.
   */
  open fun connectionClosed(connection: Connection) {}

  /**
   * Invoked when a call is assigned a particular connection.
   */
  open fun connectionAcquired(
    connection: Connection,
    call: Call,
  ) {}

  /**

  )

  fun connectionConnectEnd(
    connection: Connection,
    route: Route,
  )

  fun connectFailed(
    route: Route,
    protocol: Protocol?,
    e: IOException,
  )

  fun connectionAcquired(connection: Connection)

  fun acquireConnectionNoEvents(connection: RealConnection)

  fun releaseConnectionNoEvents(): Socket?

  fun connectionReleased(connection: Connection)

 * **ExchangeFinder** chooses which connection carries each exchange. Where possible it will use the same connection for all exchanges in a single call. It prefers reusing pooled connections over establishing new connections.      

#### Per-Connection Locks

A **Manager** is used to manage all incoming and outgoing connections to a server.

On startup all remote servers must be specified. 
From that individual connections will be spawned to each remote server, 
or incoming requests will be hooked up to the appropriate connection.

To get a connection to a specific server, use `Manager.Connection(host)` to get a connection to the specified host.
From this connection individual requests can be made.

  }

  @Test
  fun staleConnectionNotReusedForNonIdempotentRequest() {
    // Capture the connection so that we can later make it stale.
    var connection: RealConnection? = null
    client =
      client.newBuilder()
        .addNetworkInterceptor(
          Interceptor { chain ->
            connection = chain.connection() as RealConnection
            chain.proceed(chain.request())
          },
        )

  override fun connectionConnectEnd(
    connection: Connection,
    route: Route,
  ) {
    poolConnectionListener.connectEnd(connection, route, call)
  }

  override fun connectionAcquired(connection: Connection) {
    eventListener.connectionAcquired(call, connection)
  }

  override fun acquireConnectionNoEvents(connection: RealConnection) {
    call.acquireConnectionNoEvents(connection)
  }

Content-Type: text/html
Content-Length: 193
Connection: keep-alive
Location: https://publicobject.com/helloworld.txt

INFO: Sending request https://publicobject.com/helloworld.txt on Connection{publicobject.com:443, proxy=DIRECT hostAddress=54.187.32.157 cipherSuite=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA protocol=http/1.1}
User-Agent: OkHttp Example
Host: publicobject.com
Connection: Keep-Alive
Accept-Encoding: gzip