# Flutter Attach## OverviewA Flutter-command that attaches to applications that have been launchedwithout `flutter run` and provides a HotRunner (enabling hot reload/restart).## UsageThere are four ways for the attach command to discover a running app:1. If the app is already running and the observatory port is known, it can beexplicitly provided to attach via the command-line, e.g. `$ flutter attach--debug-port 12345`1. If the app is already running and the platform is iOS, attach can use mDNSto lookup the observatory port via the application ID, with just `$ flutterattach`1. If the platform is Fuchsia the module name must be provided, e.g. `$flutter attach --module=mod_name`. This can be called either before or afterthe application is started, attach will poll the device if it cannotimmediately discover the port1. On other platforms (i.e. Android), if the app is not yet running attachwill listen and wait for the app to be (manually) started with the defaultcommand: `$ flutter attach`## SourceSee the [source](https://github.com/flutter/flutter/blob/master/packages/flutter_tools/lib/src/commands/attach.dart) for the attach command.