code: func (c *Client) WriteCommand(handle uint16, value []byte) error {
  	if len(value) > c.l2c.TxMTU()-3 {
  		return ErrInvalidArgument
  	}
  
  	// Acquire and reuse the txBuf, and release it after usage.
  	txBuf := <-c.chTxBuf
  	defer func() { c.chTxBuf <- txBuf }()
  
  	req := WriteCommand(txBuf[:3+len(value)])
  	req.SetAttributeOpcode()
  	req.SetAttributeHandle(handle)
  	req.SetAttributeValue(value)
  
  	return c.sendCmd(req)
  }
docs: // WriteCommand requests the server to write the value of an attribute, typically
  // into a control-point attribute. [Vol 3, Part F, 3.4.5.3]