private var refusedStreamCount = 0

  /**
   * The maximum number of concurrent streams that can be carried by this connection. If
   * `allocations.size() < allocationLimit` then new streams can be created on this connection.
   */
  internal var allocationLimit = 1
    private set

  /** Current calls carried by this connection. */
  val calls = mutableListOf<Reference<RealCall>>()