*
   * Writes are subject to the write window of the stream and the connection. Until there is a
   * window sufficient to send [byteCount], the caller will block. For example, a user of
   * `HttpURLConnection` who flushes more bytes to the output stream than the connection's write
   * window will block.
   *
   * Zero [byteCount] writes are not subject to flow control and will not block. The only use case