val nameBuf = Buffer()
        val labels = host.split('.').dropLastWhile { it.isEmpty() }
        for (label in labels) {
          val utf8ByteCount = label.utf8Size()
          require(utf8ByteCount == label.length.toLong()) { "non-ascii hostname: $host" }
          nameBuf.writeByte(utf8ByteCount.toInt())
          nameBuf.writeUtf8(label)
        }
        nameBuf.writeByte(0) // end