FXMLDocumentController.java

    @FXML
    private void conectar(ActionEvent event) {

        if (btnConectar.getText().equals("Conectar")) {

            porta = SerialPort.getCommPort(cbPortas.getSelectionModel().getSelectedItem().toString());
            porta.setComPortTimeouts(SerialPort.TIMEOUT_SCANNER, 0, 0);

            if (porta.openPort()) {
                btnConectar.setText("Desconectar");
                cbPortas.setDisable(true);
            }

        } else {

            porta.closePort();
            cbPortas.setDisable(false);
            btnConectar.setText("Conectar");

        }
    }