private fun readMessageFrame() {
    val opcode = this.opcode
    if (opcode != OPCODE_TEXT && opcode != OPCODE_BINARY) {
      throw ProtocolException("Unknown opcode: ${opcode.toHexString()}")
    }

    readMessage()

    if (readingCompressedMessage) {
      val messageInflater =
        this.messageInflater
          ?: MessageInflater(noContextTakeover).also { this.messageInflater = it }

	if err != nil {
		return nil, err
	}

	_, _, err = z.u.WriteMsgUnix(data, rights, nil)
	if err != nil {
		return nil, err
	}

	// wait for ack
	return z.readMessage(readWriteDeadline)
}

func (z *ZtunnelConnection) readMessage(timeout time.Duration) (*zdsapi.WorkloadResponse, error) {
	m, _, err := readProto[zdsapi.WorkloadResponse](z.u, timeout, nil)
	return m, err
}