WEB-11110 Wrong error message "Built-in HTTP Server on custom port disabled"

platform/built-in-server/src/org/jetbrains/builtInWebServer/BuiltInServerConfigurableUi.java

@@ -17,6 +17,11 @@ class BuiltInServerConfigurableUi implements ConfigurableUi<BuiltInServerOptions
   public BuiltInServerConfigurableUi() {
     portLabel.setLabelFor(builtInServerPort);
     builtInServerPort.setMin(1024);
+    builtInServerPort.addChangeListener(e -> {
+      boolean isEnabled = builtInServerPort.getNumber() != BuiltInServerOptions.DEFAULT_PORT;
+      builtInServerAvailableExternallyCheckBox.setEnabled(isEnabled);
+      builtInServerAvailableExternallyCheckBox.setToolTipText(isEnabled ? null : "Can’t be enabled for default port. Please change it.");
+    });
   }
 
   @Override

platform/built-in-server/src/org/jetbrains/builtInWebServer/BuiltInServerOptions.java

@@ -29,7 +29,7 @@ import java.util.Collections;
   storages = @Storage("other.xml")
 )
 public class BuiltInServerOptions implements PersistentStateComponent<BuiltInServerOptions>, Getter<BuiltInServerOptions> {
-  private static final int DEFAULT_PORT = 63342;
+  public static final int DEFAULT_PORT = 63342;
 
   @Attribute
   public int builtInServerPort = DEFAULT_PORT;

platform/built-in-server/src/org/jetbrains/ide/BuiltInServerManagerImpl.java

@@ -74,7 +74,7 @@ public class BuiltInServerManagerImpl extends BuiltInServerManager implements Ap
   private static int getDefaultPort() {
     if (System.getProperty(PROPERTY_RPC_PORT) == null) {
       // Default port will be occupied by main idea instance - define the custom default to avoid searching of free port
-      return ApplicationManager.getApplication().isUnitTestMode() ? 64463 : 63342;
+      return ApplicationManager.getApplication().isUnitTestMode() ? 64463 : BuiltInServerOptions.DEFAULT_PORT;
     }
     else {
       return Integer.parseInt(System.getProperty(PROPERTY_RPC_PORT));