taking screenshots works just fine with new approach

packages/patrol/lib/patrol_driver.dart

@@ -53,13 +53,24 @@ Future<void> _initCommunication({
     }
 
     final method = event.extensionData!.data['method'] as String;
+    final requestId = event.extensionData!.data['request_id'] as int;
     switch (method) {
       case 'take_screenshot':
-        _takeScreenshot(
-          event.extensionData!.data['args'] as Map<String, dynamic>,
+        bool status;
+        try {
+          _takeScreenshot(
+            event.extensionData!.data['args'] as Map<String, dynamic>,
+          );
+          status = true;
+        } catch (err) {
+          status = false;
+        }
+
+        vmService.callServiceExtension(
+          'ext.flutter.patrol',
+          isolateId: isolateId,
+          args: <String, dynamic>{'request_id': requestId, 'status': status},
         );
-
-        vmService.callServiceExtension('patrol', isolateId: isolateId);
         break;
       default:
         throw StateError('unknown method $method');
@@ -73,14 +84,12 @@ void _takeScreenshot(Map<String, dynamic> args) {
     print('Error: DRIVER_DEVICE_ID is not set');
     io.exit(1);
   }
-  print('DRIVER_DEVICE_ID: $deviceId');
 
   final deviceOs = io.Platform.environment['DRIVER_DEVICE_OS'];
   if (deviceOs == null || deviceOs.isEmpty) {
     print('Error: DRIVER_DEVICE_OS is not set');
     io.exit(1);
   }
-  print('DRIVER_DEVICE_OS: $deviceOs');
 
   final screenshotName = args['name'] as String?;
   if (screenshotName == null) {

packages/patrol/lib/src/native/binding.dart

@@ -1,9 +1,23 @@
+import 'dart:async';
 import 'dart:developer';
 
 import 'package:flutter/foundation.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:integration_test/integration_test.dart';
-import 'package:vm_service/vm_service.dart' as vm;
+
+class _Response {
+  factory _Response.fromJson(Map<String, dynamic> json) {
+    return _Response._(
+      int.parse(json['request_id'] as String),
+      json['status'] == 'true',
+    );
+  }
+
+  const _Response._(this.id, this.ok);
+
+  final int id;
+  final bool ok;
+}
 
 // ignore: avoid_print
 void _defaultPrintLogger(String message) => print('PatrolBinding: $message');
@@ -25,14 +39,9 @@ class PatrolBinding extends IntegrationTestWidgetsFlutterBinding {
 
   final _logger = _defaultPrintLogger;
 
-  /// ID of the Isolate which the host driver script is running in.
-  ///
-  /// Has the form of e.g "isolates/1566121372315359".
-  late String driverIsolateId;
+  int _latestEventId = 0;
 
-  /// Dart VM service (aka Dart Observatory server) running in the main isolate
-  /// of the Dart VM which is running the test driver script.
-  late vm.VmService vmService;
+  final _controller = StreamController<_Response>.broadcast();
 
   // TODO: Remove once https://github.com/flutter/flutter/pull/108430 is
   // available on the stable channel
@@ -49,17 +58,41 @@ class PatrolBinding extends IntegrationTestWidgetsFlutterBinding {
     }
   }
 
+  @override
+  void initServiceExtensions() {
+    super.initServiceExtensions();
+
+    if (!kReleaseMode) {
+      registerServiceExtension(
+        name: 'patrol',
+        callback: (args) async {
+          _controller.add(_Response.fromJson(args));
+          return <String, String>{};
+        },
+      );
+      _logger('registered service extension ext.flutter.patrol');
+    }
+  }
+
   /// Takes a screenshot using the `flutter screenshot` command.
   ///
   /// The screenshot is placed in [path], named [name], and has .png extension.
   Future<void> takeFlutterScreenshot({
     required String name,
     required String path,
   }) async {
+    final eventId = ++_latestEventId;
+
     postEvent('patrol', <String, dynamic>{
       'method': 'take_screenshot',
+      'request_id': eventId,
       'args': {'name': name, 'path': path}
     });
+
+    final resp = await _controller.stream.firstWhere((r) => r.id == eventId);
+    if (!resp.ok) {
+      throw StateError('event with request_id $eventId failed');
+    }
   }
 
   /// The singleton instance of this object.