sink.flush()
    }
  }

  /**
   * Send a connection-level ping to the peer. `ack` indicates this is a reply. The data in
   * `payload1` and `payload2` opaque binary, and there are no rules on the content.
   */
  @Throws(IOException::class)
  fun ping(
    ack: Boolean,
    payload1: Int,
    payload2: Int,
  ) {
    this.withLock {
      if (closed) throw IOException("closed")
      frameHeader(

    This includes overly-long domain names (longer than 253 characters), overly-long labels (more
    than 63 characters between dots), and empty labels.
 *  New: Don't include the `Content-Length` header in multipart bodies. Servers must delimit
    OkHttp's request bodies using the boundary only. (This change makes OkHttp more consistent with
    browsers and other HTTP clients.)