fixes #263

main/ui/src/main/java/org/cryptomator/ui/controllers/SettingsController.java

@@ -43,6 +43,9 @@ public class SettingsController extends LocalizedFXMLViewController {
 	@FXML
 	private TextField portField;
 
+	@FXML
+	private Label useIpv6Label;
+
 	@FXML
 	private CheckBox useIpv6Checkbox;
 
@@ -55,7 +58,8 @@ public class SettingsController extends LocalizedFXMLViewController {
 		checkForUpdatesCheckbox.setSelected(settings.isCheckForUpdatesEnabled() && !areUpdatesManagedExternally());
 		portField.setText(String.valueOf(settings.getPort()));
 		portField.addEventFilter(KeyEvent.KEY_TYPED, this::filterNumericKeyEvents);
-		useIpv6Checkbox.setDisable(!SystemUtils.IS_OS_WINDOWS);
+		useIpv6Label.setVisible(SystemUtils.IS_OS_WINDOWS);
+		useIpv6Checkbox.setVisible(SystemUtils.IS_OS_WINDOWS);
 		useIpv6Checkbox.setSelected(SystemUtils.IS_OS_WINDOWS && settings.shouldUseIpv6());
 		versionLabel.setText(String.format(localization.getString("settings.version.label"), applicationVersion().orElse("SNAPSHOT")));
 
@@ -81,7 +85,7 @@ public class SettingsController extends LocalizedFXMLViewController {
 	private void portDidChange(String newValue) {
 		try {
 			int port = Integer.parseInt(newValue);
-			if (port < Settings.MIN_PORT || port > Settings.MAX_PORT) {
+			if (!settings.isPortValid(port)) {
 				settings.setPort(Settings.DEFAULT_PORT);
 			} else {
 				settings.setPort(port);

main/ui/src/main/java/org/cryptomator/ui/settings/Settings.java

@@ -93,8 +93,8 @@ public class Settings implements Serializable {
 		}
 	}
 
-	private boolean isPortValid(int port) {
-		return port == DEFAULT_PORT || port >= MIN_PORT && port <= MAX_PORT;
+	public boolean isPortValid(int port) {
+		return port == DEFAULT_PORT || port >= MIN_PORT && port <= MAX_PORT || port == 0;
 	}
 
 	public boolean shouldUseIpv6() {

main/ui/src/main/resources/fxml/settings.fxml

@@ -38,7 +38,7 @@
 			<TextField GridPane.rowIndex="1" GridPane.columnIndex="1" fx:id="portField" cacheShape="true" cache="true" promptText="%settings.port.prompt" />
 			
 			<!-- Row 2 -->
-			<Label GridPane.rowIndex="2" GridPane.columnIndex="0" text="%settings.useipv6.label" cacheShape="true" cache="true" />
+			<Label GridPane.rowIndex="2" GridPane.columnIndex="0" fx:id="useIpv6Label" text="%settings.useipv6.label" cacheShape="true" cache="true" />
 			<CheckBox GridPane.rowIndex="2" GridPane.columnIndex="1" fx:id="useIpv6Checkbox" cacheShape="true" cache="true" />
 		</children>
 	</GridPane>