private var protocol: Protocol? = null
  private var source: BufferedSource? = null
  private var sink: BufferedSink? = null
  private var connection: RealConnection? = null

  /** True if this connection is ready for use, including TCP, tunnels, and TLS. */
  override val isReady: Boolean
    get() = protocol != null

  private fun copy(
    attempt: Int = this.attempt,
    tunnelRequest: Request? = this.tunnelRequest,