private var maxFrameSize: Int = INITIAL_MAX_FRAME_SIZE
  private var closed: Boolean = false
  val hpackWriter: Hpack.Writer = Hpack.Writer(out = hpackBuffer)

  @Throws(IOException::class)
  fun connectionPreface() {
    this.withLock {
      if (closed) throw IOException("closed")
      if (!client) return // Nothing to write; servers don't send connection headers!
      if (logger.isLoggable(FINE)) {