sdk/lib/_internal/vm/bin/vmservice_server.dart - sdk.git - Git at Google

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

 part of 'dart:vmservice_io';

 // TODO(48602): deprecate SILENT_OBSERVATORY in favor of SILENT_VM_SERVICE
 bool silentObservatory = bool.fromEnvironment('SILENT_OBSERVATORY');
 bool silentVMService = bool.fromEnvironment('SILENT_VM_SERVICE');

 void serverPrint(String s) {
   if (silentObservatory || silentVMService) {
     // We've been requested to be silent.
     return;
   }
   print(s);
 }

 class WebSocketClient extends Client {
   static const int parseErrorCode = 4000;
   static const int binaryMessageErrorCode = 4001;
   static const int notMapErrorCode = 4002;
   static const int idErrorCode = 4003;
   final WebSocket socket;

   WebSocketClient(this.socket, VMService service) : super(service) {
     socket.listen((message) => onWebSocketMessage(message));
     socket.done.then((_) => close());
   }

   Future<void> disconnect() => socket.close();

   void onWebSocketMessage(message) {
     if (message is String) {
       dynamic jsonObj;
       try {
         jsonObj = json.decode(message);
       } catch (e) {
         socket.close(parseErrorCode, 'Message parse error: $e');
         return;
       }
       if (jsonObj is! Map<String, dynamic>) {
         socket.close(notMapErrorCode, 'Message must be a JSON map.');
         return;
       }
       final Map<String, dynamic> map = jsonObj;
       final rpc = Message.fromJsonRpc(this, map);
       switch (rpc.type) {
         case MessageType.Request:
           onRequest(rpc);
           break;
         case MessageType.Notification:
           onNotification(rpc);
           break;
         case MessageType.Response:
           onResponse(rpc);
           break;
       }
     } else {
       socket.close(binaryMessageErrorCode, 'Message must be a string.');
     }
   }

   void post(Response? result) {
     if (result == null) {
       // The result of a notification event. Do nothing.
       return;
     }
     try {
       switch (result.kind) {
         case ResponsePayloadKind.String:
         case ResponsePayloadKind.Binary:
           socket.add(result.payload);
           break;
         case ResponsePayloadKind.Utf8String:
           socket.addUtf8Text(result.payload as List<int>);
           break;
       }
     } on StateError catch (_) {
       // VM has shutdown, do nothing.
       return;
     }
   }

   Map<String, dynamic> toJson() => {
     ...super.toJson(),
     'type': 'WebSocketClient',
     'socket': '$socket',
   };
 }

 class HttpRequestClient extends Client {
   static final jsonContentType = ContentType(
     'application',
     'json',
     charset: 'utf-8',
   );
   final HttpRequest request;

   HttpRequestClient(this.request, VMService service)
     : super(service, sendEvents: false);

   Future<void> disconnect() async {
     await request.response.close();
     close();
   }

   void post(Response? result) {
     if (result == null) {
       // The result of a notification event. Nothing to do other than close the
       // connection.
       close();
       return;
     }

     HttpResponse response = request.response;
     // We closed the connection for bad origins earlier.
     response.headers.add('Access-Control-Allow-Origin', '*');
     response.headers.contentType = jsonContentType;
     switch (result.kind) {
       case ResponsePayloadKind.String:
         response.write(result.payload);
         break;
       case ResponsePayloadKind.Utf8String:
         response.add(result.payload);
         break;
       case ResponsePayloadKind.Binary:
         throw 'Can not handle binary responses';
     }
     response.close();
     close();
   }

   Map<String, dynamic> toJson() {
     final map = super.toJson();
     map['type'] = 'HttpRequestClient';
     map['request'] = '$request';
     return map;
   }
 }

 /// Responsible for launching a DevTools instance when the service is started
 /// via SIGQUIT.
 class _DebuggingSession {
   Future<bool> start(
     Uri serverAddress,
     String host,
     String port,
     bool disableServiceAuthCodes,
     bool enableDevTools,
   ) async {
     // This code is part of the SDK and it is ok to have a reference to the
     // internals of the Dart SDK in terms of location of the snapshot etc.
     // It is more efficient doing it this way instead of invoking the Dart CLI
     // with the 'development-service' command which would then dispatch to the
     // Dart AOT runtime.
     final dartDir = File(Platform.executable).parent.path;
     final suffix = Platform.isWindows ? '.exe' : '';
     final dartAotRuntime = 'dartaotruntime${suffix}';
     final dart = 'dart${suffix}';
     var executable = [dartDir, dartAotRuntime].join(Platform.pathSeparator);
     var script = [
       dartDir,
       'snapshots',
       'dds_aot.dart.snapshot',
     ].join(Platform.pathSeparator);
     if (FileSystemEntity.typeSync(script) == FileSystemEntityType.notFound) {
       script = [dartDir, 'dds_aot.dart.snapshot'].join(Platform.pathSeparator);
       if (FileSystemEntity.typeSync(script) == FileSystemEntityType.notFound) {
         // We could be running on IA32 architecture so check if the JIT
         // snapshot is available.
         executable = [dartDir, dart].join(Platform.pathSeparator);
         script = [dartDir, 'dds.dart.snapshot'].join(Platform.pathSeparator);
         if (FileSystemEntity.typeSync(script) ==
             FileSystemEntityType.notFound) {
           script = 'development-service';
         }
       }
     }

     // If the directory of dart is '.' it's likely that dart is on the user's
     // PATH. If so, './dart' might not exist and we should be using 'dart'
     // instead.
     if (dartDir == '.' &&
         (FileSystemEntity.typeSync(executable)) ==
             FileSystemEntityType.notFound) {
       executable = dart;
     }
     var process = await Process.start(executable, [
       script,
       '--vm-service-uri=$serverAddress',
       '--bind-address=$host',
       '--bind-port=$port',
       if (disableServiceAuthCodes) '--disable-service-auth-codes',
       if (enableDevTools) '--serve-devtools',
       if (_enableServicePortFallback) '--enable-service-port-fallback',
     ], mode: ProcessStartMode.detachedWithStdio);
     if (process == null) {
       stderr.writeln('Could not start the VM service: Process.start failed\n');
       return false;
     }
     _process = process;

     // DDS will close stderr once it's finished launching.
     final launchResultStderr = await _process.stderr
         .transform(utf8.decoder)
         .join();

     void printError(String details) =>
         stderr.writeln('Could not start the VM service: $details');

     try {
       final result = json.decode(launchResultStderr) as Map<String, dynamic>;
       if (result case {'state': 'started'}) {
         if (result case {'devToolsUri': String devToolsUri}) {
           // NOTE: update pkg/dartdev/lib/src/commands/run.dart if this message
           // is changed to ensure consistency.
           const devToolsMessagePrefix =
               'The Dart DevTools debugger and profiler is available at:';
           serverPrint('$devToolsMessagePrefix $devToolsUri');
         }
         if (result case {'dtd': {'uri': String dtdUri}} when _printDtd) {
           serverPrint('The Dart Tooling Daemon (DTD) is available at: $dtdUri');
         }
       } else {
         printError(result['error'] ?? result);
         return false;
       }
     } catch (_) {
       // Malformed JSON was likely encountered, so output the entirety of
       // stderr in the error message.
       printError("Couldn't parse JSON: ${launchResultStderr}");
       return false;
     }
     return true;
   }

   void shutdown() => _process.kill();

   late Process _process;
 }

 class Server {
   static const WEBSOCKET_PATH = '/ws';
   static const ROOT_REDIRECT_PATH = '/index.html';

   final VMService _service;
   final String _ip;
   final bool _originCheckDisabled;
   final bool _authCodesDisabled;
   final bool _enableServicePortFallback;
   final String? _serviceInfoFilename;
   HttpServer? _httpServer;

   bool get running => _running;
   bool _running = false;

   bool acceptNewWebSocketConnections = true;
   int _port = -1;
   // Ensures only one server is started even if many requests to launch
   // the server come in concurrently.
   Completer<bool>? _startingCompleter;

   _DebuggingSession? _ddsInstance;

   /// Returns the server address including the auth token.
   Uri? get serverAddress {
     // If DDS is connected it should be treated as the "true" VM service and be
     // advertised as such.
     if (_service.ddsUri != null) {
       return _service.ddsUri;
     }
     final server = _httpServer;
     if (server != null) {
       final ip = server.address.address;
       final port = server.port;
       final path = !_authCodesDisabled ? '$serviceAuthToken/' : '/';
       return Uri(scheme: 'http', host: ip, port: port, path: path);
     }
     return null;
   }

   // On Fuchsia, authentication codes are disabled by default. To enable, the authentication token
   // would have to be written into the hub alongside the port number.
   Server(
     this._service,
     this._ip,
     this._port,
     this._originCheckDisabled,
     bool authCodesDisabled,
     this._serviceInfoFilename,
     this._enableServicePortFallback,
   ) : _authCodesDisabled = (authCodesDisabled || Platform.isFuchsia);

   Future<void> startup() async {
     if (running) {
       // Already running.
       return;
     }

     {
       final startingCompleter = _startingCompleter;
       if (startingCompleter != null) {
         if (!startingCompleter.isCompleted) {
           await startingCompleter.future;
         }
         return;
       }
     }

     final startingCompleter = Completer<bool>();
     _startingCompleter = startingCompleter;
     // Startup HTTP server.
     Future<bool> startServer() async {
       try {
         var address;
         var addresses = await InternetAddress.lookup(_ip);
         // Prefer IPv4 addresses.
         for (int i = 0; i < addresses.length; i++) {
           address = addresses[i];
           if (address.type == InternetAddressType.IPv4) break;
         }
         _httpServer = await HttpServer.bind(address, _port);
       } catch (e, st) {
         if (_port != 0 && _enableServicePortFallback) {
           serverPrint(
             'Failed to bind Dart VM service HTTP server to port $_port. '
             'Falling back to automatic port selection',
           );
           _port = 0;
           return await startServer();
         } else {
           serverPrint(
             'Could not start Dart VM service HTTP server:\n'
             '$e\n$st',
           );
           _notifyServerState('');
           onServerAddressChange(null);
           return false;
         }
       }
       return true;
     }

     if (!(await startServer())) {
       startingCompleter.complete(true);
       return;
     }
     if (_service.isExiting) {
       serverPrint(
         'Dart VM service HTTP server exiting before listening as '
         'vm service has received exit request\n',
       );
       startingCompleter.complete(true);
       await shutdown(true);
       return;
     }
     final server = _httpServer!;
     server.listen(_requestHandler, cancelOnError: true);

     if (_waitForDdsToAdvertiseService) {
       _ddsInstance = _DebuggingSession();
       await _ddsInstance!.start(
         serverAddress!,
         _ddsIP,
         _ddsPort.toString(),
         _authCodesDisabled,
         _serveDevtools,
       );
     } else {
       await outputConnectionInformation();
     }
     // Server is up and running.
     _running = true;
     _notifyServerState(serverAddress.toString());
     onServerAddressChange('$serverAddress');
     startingCompleter.complete(true);
   }

   Future<void> shutdown(bool forced) async {
     // If start is pending, wait for it to complete.
     if (_startingCompleter != null) {
       if (!_startingCompleter!.isCompleted) {
         await _startingCompleter!.future;
       }
     }

     final server = _httpServer;
     if (server == null) {
       // Not started.
       return;
     }

     if (Platform.isFuchsia) {
       _cleanupFuchsiaState(server.port);
     }

     final address = serverAddress!;

     try {
       // Shutdown HTTP server and subscription.
       await server.close(force: forced);
       if (!_service.isExiting) {
         // Only print this message if the service has been toggled off, not
         // when the VM is exiting.
         serverPrint('Dart VM service no longer listening on $address');
       }
     } catch (e, st) {
       serverPrint('Could not shutdown Dart VM service HTTP server:\n$e\n$st\n');
     } finally {
       _ddsInstance?.shutdown();
       _ddsInstance = null;
       _httpServer = null;
       _startingCompleter = null;
       _running = false;
       _notifyServerState('');
       onServerAddressChange(null);
     }
   }

   Future<void> outputConnectionInformation() async {
     serverPrint('The Dart VM service is listening on $serverAddress');
     if (Platform.isFuchsia) {
       _writeFuchsiaState(_httpServer!.port);
     }
     final serviceInfoFilenameLocal = _serviceInfoFilename;
     if (serviceInfoFilenameLocal != null &&
         serviceInfoFilenameLocal.isNotEmpty) {
       await _dumpServiceInfoToFile(serviceInfoFilenameLocal);
     }
   }

   bool _isAllowedOrigin(String origin) {
     Uri uri;
     try {
       uri = Uri.parse(origin);
     } catch (_) {
       return false;
     }

     // Explicitly add localhost and 127.0.0.1 on any port (necessary for
     // adb port forwarding).
     if ((uri.host == 'localhost') ||
         (uri.host == '::1') ||
         (uri.host == '127.0.0.1')) {
       return true;
     }

     final server = _httpServer!;
     if ((uri.port == server.port) &&
         ((uri.host == server.address.address) ||
             (uri.host == server.address.host))) {
       return true;
     }

     return false;
   }

   bool _originCheck(HttpRequest request) {
     if (_originCheckDisabled) {
       // Always allow.
       return true;
     }
     // First check the web-socket specific origin.
     List<String>? origins = request.headers['Sec-WebSocket-Origin'];
     if (origins == null) {
       // Fall back to the general Origin field.
       origins = request.headers['Origin'];
     }
     if (origins == null) {
       // No origin sent. This is a non-browser client or a same-origin request.
       return true;
     }
     for (final origin in origins) {
       if (_isAllowedOrigin(origin)) {
         return true;
       }
     }
     return false;
   }

   /// Checks the [requestUri] for the service auth token and returns the path
   /// as a String. If the service auth token check fails, returns null.
   /// Returns a Uri if a redirect is required.
   dynamic _checkAuthTokenAndGetPath(Uri requestUri) {
     if (_authCodesDisabled) {
       return requestUri.path == '/' ? ROOT_REDIRECT_PATH : requestUri.path;
     }
     final List<String> requestPathSegments = requestUri.pathSegments;
     if (requestPathSegments.isEmpty) {
       // Malformed.
       return null;
     }
     // Check that we were given the auth token.
     final authToken = requestPathSegments[0];
     if (authToken != serviceAuthToken) {
       // Malformed.
       return null;
     }
     // Missing a trailing '/'. We'll need to redirect to serve
     // ROOT_REDIRECT_PATH correctly, otherwise the response is misinterpreted.
     if (requestPathSegments.length == 1) {
       // requestPathSegments is unmodifiable. Copy it.
       final pathSegments = List<String>.from(requestPathSegments);

       // Adding an empty string to the path segments results in the path having
       // a trailing '/'.
       pathSegments.add('');

       return requestUri.replace(pathSegments: pathSegments);
     }
     // Construct the actual request path by chopping off the auth token.
     return (requestPathSegments[1] == '')
         ? ROOT_REDIRECT_PATH
         : '/${requestPathSegments.sublist(1).join('/')}';
   }

   Future<void> _processDevFSRequest(HttpRequest request) async {
     String? fsName;
     String? fsPath;
     Uri? fsUri;

     try {
       // Extract the fs name and fs path from the request headers.
       fsName = request.headers['dev_fs_name']![0];

       // Prefer Uri encoding first, then fallback to path encoding.
       if (request.headers['dev_fs_uri_b64'] case [String base64Uri]) {
         fsUri = Uri.parse(utf8.decode(base64.decode(base64Uri)));
       } else if (request.headers['dev_fs_path_b64'] case [String base64Uri]) {
         fsPath = utf8.decode(base64.decode(base64Uri));
       } else if (request.headers['dev_fs_path'] case [String path]) {
         fsPath = path;
       }
     } catch (_) {
       /* ignore */
     }

     try {
       final result = await _service.devfs.handlePutStream(
         fsName,
         fsPath,
         fsUri,
         request.cast<List<int>>().transform(gzip.decoder),
       );

       request.response.headers.contentType = HttpRequestClient.jsonContentType;
       request.response.write(result);
     } catch (e, st) {
       request.response.statusCode = HttpStatus.internalServerError;
       request.response.write(e);
     } finally {
       request.response.close();
     }
   }

   void _handleWebSocketRequest(HttpRequest request) {
     final subprotocols = request.headers['sec-websocket-protocol'];
     if (acceptNewWebSocketConnections) {
       WebSocketTransformer.upgrade(
         request,
         protocolSelector: subprotocols == null
             ? null
             : (_) => 'implicit-redirect',
         compression: CompressionOptions.compressionOff,
       ).then((WebSocket webSocket) {
         WebSocketClient(webSocket, _service);
       });
     } else {
       // Attempt to redirect client to the DDS instance.
       request.response.redirect(_service.ddsUri!);
     }
   }

   Future<void> _redirectToDevTools(HttpRequest request) async {
     final ddsUri = _service.ddsUri;
     if (ddsUri == null) {
       request.response.headers.contentType = ContentType.text;
       request.response.write(
         'This VM does not have a registered Dart '
         'Development Service (DDS) instance and is not currently serving '
         'Dart DevTools.',
       );
       request.response.close();
       return;
     }
     // We build this path manually rather than manipulating ddsUri directly
     // as the resulting path requires an unencoded '#'. The Uri class will
     // always encode '#' as '%23' in paths to avoid conflicts with fragments,
     // which will result in the redirect failing.
     final path = StringBuffer();
     // Add authentication code to the path.
     if (ddsUri.pathSegments.length > 1) {
       path.writeAll([
         ddsUri.pathSegments
             .sublist(0, ddsUri.pathSegments.length - 1)
             .join('/'),
         '/',
       ]);
     }
     final queryComponent = Uri.encodeQueryComponent(
       ddsUri.replace(scheme: 'ws', path: '${path}ws').toString(),
     );
     path.writeAll(['devtools/', '?uri=$queryComponent']);
     final redirectUri = Uri.parse('http://${ddsUri.host}:${ddsUri.port}/$path');
     request.response.redirect(redirectUri);
     return;
   }

   Future<void> _requestHandler(HttpRequest request) async {
     if (!_originCheck(request)) {
       // This is a cross origin attempt to connect
       request.response.statusCode = HttpStatus.forbidden;
       request.response.write('forbidden origin');
       request.response.close();
       return;
     }
     if (request.method == 'PUT') {
       // PUT requests are forwarded to DevFS for processing.
       await _processDevFSRequest(request);
       return;
     }
     if (request.method != 'GET') {
       // Not a GET request. Do nothing.
       request.response.statusCode = HttpStatus.methodNotAllowed;
       request.response.write('method not allowed');
       request.response.close();
       return;
     }

     final result = _checkAuthTokenAndGetPath(request.uri);
     if (result == null) {
       // Either no authentication code was provided when one was expected or an
       // incorrect authentication code was provided.
       request.response.statusCode = HttpStatus.forbidden;
       request.response.write('missing or invalid authentication code');
       request.response.close();
       return;
     } else if (result is Uri) {
       // The URI contains the valid auth token but is missing a trailing '/'.
       // Redirect to the same URI with the trailing '/' to correctly serve
       // index.html.
       request.response.redirect(result);
       return;
     }

     final String path = result;
     if (path == WEBSOCKET_PATH) {
       _handleWebSocketRequest(request);
       return;
     }
     // Don't redirect HTTP VM service requests, just requests for DevTools
     // assets.
     if (path == ROOT_REDIRECT_PATH) {
       await _redirectToDevTools(request);
       return;
     }
     // HTTP based service request.
     final client = HttpRequestClient(request, _service);
     final message = Message.fromUri(
       client,
       Uri(path: path, queryParameters: request.uri.queryParameters),
     );
     client.onRequest(message); // exception free, no need to try catch
   }

   Future<File> _dumpServiceInfoToFile(String serviceInfoFilenameLocal) async {
     final serviceInfo = <String, dynamic>{'uri': serverAddress.toString()};
     const kFileScheme = 'file://';
     // There's lots of URI parsing weirdness as Uri.parse doesn't do the right
     // thing with Windows drive letters. Only use Uri.parse with known file
     // URIs, and use Uri.file otherwise to properly handle drive letters in
     // paths.
     final uri = serviceInfoFilenameLocal.startsWith(kFileScheme)
         ? Uri.parse(serviceInfoFilenameLocal)
         : Uri.file(serviceInfoFilenameLocal);
     final file = File.fromUri(uri);
     return file.writeAsString(json.encode(serviceInfo));
   }

   void _writeFuchsiaState(int port) {
     // Create a file with the port number.
     final tmp = Directory.systemTemp.path;
     final path = '$tmp/dart.services/${port}';
     serverPrint('Creating $path');
     File(path).createSync(recursive: true);
   }

   void _cleanupFuchsiaState(int port) {
     // Remove the file with the port number.
     final tmp = Directory.systemTemp.path;
     final path = '$tmp/dart.services/$port';
     serverPrint('Deleting $path');
     File(path).deleteSync();
   }
 }

 @pragma("vm:external-name", "VMServiceIO_NotifyServerState")
 external void _notifyServerState(String uri);
	// Copyright (c) 2013, the Dart project authors. Please see the AUTHORS file
	// for details. All rights reserved. Use of this source code is governed by a
	// BSD-style license that can be found in the LICENSE file.

	part of 'dart:vmservice_io';

	// TODO(48602): deprecate SILENT_OBSERVATORY in favor of SILENT_VM_SERVICE
	bool silentObservatory = bool.fromEnvironment('SILENT_OBSERVATORY');
	bool silentVMService = bool.fromEnvironment('SILENT_VM_SERVICE');

	void serverPrint(String s) {
	if (silentObservatory \|\| silentVMService) {
	// We've been requested to be silent.
	return;
	}
	print(s);
	}

	class WebSocketClient extends Client {
	static const int parseErrorCode = 4000;
	static const int binaryMessageErrorCode = 4001;
	static const int notMapErrorCode = 4002;
	static const int idErrorCode = 4003;
	final WebSocket socket;

	WebSocketClient(this.socket, VMService service) : super(service) {
	socket.listen((message) => onWebSocketMessage(message));
	socket.done.then((_) => close());
	}

	Future<void> disconnect() => socket.close();

	void onWebSocketMessage(message) {
	if (message is String) {
	dynamic jsonObj;
	try {
	jsonObj = json.decode(message);
	} catch (e) {
	socket.close(parseErrorCode, 'Message parse error: $e');
	return;
	}
	if (jsonObj is! Map<String, dynamic>) {
	socket.close(notMapErrorCode, 'Message must be a JSON map.');
	return;
	}
	final Map<String, dynamic> map = jsonObj;
	final rpc = Message.fromJsonRpc(this, map);
	switch (rpc.type) {
	case MessageType.Request:
	onRequest(rpc);
	break;
	case MessageType.Notification:
	onNotification(rpc);
	break;
	case MessageType.Response:
	onResponse(rpc);
	break;
	}
	} else {
	socket.close(binaryMessageErrorCode, 'Message must be a string.');
	}
	}

	void post(Response? result) {
	if (result == null) {
	// The result of a notification event. Do nothing.
	return;
	}
	try {
	switch (result.kind) {
	case ResponsePayloadKind.String:
	case ResponsePayloadKind.Binary:
	socket.add(result.payload);
	break;
	case ResponsePayloadKind.Utf8String:
	socket.addUtf8Text(result.payload as List<int>);
	break;
	}
	} on StateError catch (_) {
	// VM has shutdown, do nothing.
	return;
	}
	}

	Map<String, dynamic> toJson() => {
	...super.toJson(),
	'type': 'WebSocketClient',
	'socket': '$socket',
	};
	}

	class HttpRequestClient extends Client {
	static final jsonContentType = ContentType(
	'application',
	'json',
	charset: 'utf-8',
	);
	final HttpRequest request;

	HttpRequestClient(this.request, VMService service)
	: super(service, sendEvents: false);

	Future<void> disconnect() async {
	await request.response.close();
	close();
	}

	void post(Response? result) {
	if (result == null) {
	// The result of a notification event. Nothing to do other than close the
	// connection.
	close();
	return;
	}

	HttpResponse response = request.response;
	// We closed the connection for bad origins earlier.
	response.headers.add('Access-Control-Allow-Origin', '*');
	response.headers.contentType = jsonContentType;
	switch (result.kind) {
	case ResponsePayloadKind.String:
	response.write(result.payload);
	break;
	case ResponsePayloadKind.Utf8String:
	response.add(result.payload);
	break;
	case ResponsePayloadKind.Binary:
	throw 'Can not handle binary responses';
	}
	response.close();
	close();
	}

	Map<String, dynamic> toJson() {
	final map = super.toJson();
	map['type'] = 'HttpRequestClient';
	map['request'] = '$request';
	return map;
	}
	}

	/// Responsible for launching a DevTools instance when the service is started
	/// via SIGQUIT.
	class _DebuggingSession {
	Future<bool> start(
	Uri serverAddress,
	String host,
	String port,
	bool disableServiceAuthCodes,
	bool enableDevTools,
	) async {
	// This code is part of the SDK and it is ok to have a reference to the
	// internals of the Dart SDK in terms of location of the snapshot etc.
	// It is more efficient doing it this way instead of invoking the Dart CLI
	// with the 'development-service' command which would then dispatch to the
	// Dart AOT runtime.
	final dartDir = File(Platform.executable).parent.path;
	final suffix = Platform.isWindows ? '.exe' : '';
	final dartAotRuntime = 'dartaotruntime${suffix}';
	final dart = 'dart${suffix}';
	var executable = [dartDir, dartAotRuntime].join(Platform.pathSeparator);
	var script = [
	dartDir,
	'snapshots',
	'dds_aot.dart.snapshot',
	].join(Platform.pathSeparator);
	if (FileSystemEntity.typeSync(script) == FileSystemEntityType.notFound) {
	script = [dartDir, 'dds_aot.dart.snapshot'].join(Platform.pathSeparator);
	if (FileSystemEntity.typeSync(script) == FileSystemEntityType.notFound) {
	// We could be running on IA32 architecture so check if the JIT
	// snapshot is available.
	executable = [dartDir, dart].join(Platform.pathSeparator);
	script = [dartDir, 'dds.dart.snapshot'].join(Platform.pathSeparator);
	if (FileSystemEntity.typeSync(script) ==
	FileSystemEntityType.notFound) {
	script = 'development-service';
	}
	}
	}

	// If the directory of dart is '.' it's likely that dart is on the user's
	// PATH. If so, './dart' might not exist and we should be using 'dart'
	// instead.
	if (dartDir == '.' &&
	(FileSystemEntity.typeSync(executable)) ==
	FileSystemEntityType.notFound) {
	executable = dart;
	}
	var process = await Process.start(executable, [
	script,
	'--vm-service-uri=$serverAddress',
	'--bind-address=$host',
	'--bind-port=$port',
	if (disableServiceAuthCodes) '--disable-service-auth-codes',
	if (enableDevTools) '--serve-devtools',
	if (_enableServicePortFallback) '--enable-service-port-fallback',
	], mode: ProcessStartMode.detachedWithStdio);
	if (process == null) {
	stderr.writeln('Could not start the VM service: Process.start failed\n');
	return false;
	}
	_process = process;

	// DDS will close stderr once it's finished launching.
	final launchResultStderr = await _process.stderr
	.transform(utf8.decoder)
	.join();

	void printError(String details) =>
	stderr.writeln('Could not start the VM service: $details');

	try {
	final result = json.decode(launchResultStderr) as Map<String, dynamic>;
	if (result case {'state': 'started'}) {
	if (result case {'devToolsUri': String devToolsUri}) {
	// NOTE: update pkg/dartdev/lib/src/commands/run.dart if this message
	// is changed to ensure consistency.
	const devToolsMessagePrefix =
	'The Dart DevTools debugger and profiler is available at:';
	serverPrint('$devToolsMessagePrefix $devToolsUri');
	}
	if (result case {'dtd': {'uri': String dtdUri}} when _printDtd) {
	serverPrint('The Dart Tooling Daemon (DTD) is available at: $dtdUri');
	}
	} else {
	printError(result['error'] ?? result);
	return false;
	}
	} catch (_) {
	// Malformed JSON was likely encountered, so output the entirety of
	// stderr in the error message.
	printError("Couldn't parse JSON: ${launchResultStderr}");
	return false;
	}
	return true;
	}

	void shutdown() => _process.kill();

	late Process _process;
	}

	class Server {
	static const WEBSOCKET_PATH = '/ws';
	static const ROOT_REDIRECT_PATH = '/index.html';

	final VMService _service;
	final String _ip;
	final bool _originCheckDisabled;
	final bool _authCodesDisabled;
	final bool _enableServicePortFallback;
	final String? _serviceInfoFilename;
	HttpServer? _httpServer;

	bool get running => _running;
	bool _running = false;

	bool acceptNewWebSocketConnections = true;
	int _port = -1;
	// Ensures only one server is started even if many requests to launch
	// the server come in concurrently.
	Completer<bool>? _startingCompleter;

	_DebuggingSession? _ddsInstance;

	/// Returns the server address including the auth token.
	Uri? get serverAddress {
	// If DDS is connected it should be treated as the "true" VM service and be
	// advertised as such.
	if (_service.ddsUri != null) {
	return _service.ddsUri;
	}
	final server = _httpServer;
	if (server != null) {
	final ip = server.address.address;
	final port = server.port;
	final path = !_authCodesDisabled ? '$serviceAuthToken/' : '/';
	return Uri(scheme: 'http', host: ip, port: port, path: path);
	}
	return null;
	}

	// On Fuchsia, authentication codes are disabled by default. To enable, the authentication token
	// would have to be written into the hub alongside the port number.
	Server(
	this._service,
	this._ip,
	this._port,
	this._originCheckDisabled,
	bool authCodesDisabled,
	this._serviceInfoFilename,
	this._enableServicePortFallback,
	) : _authCodesDisabled = (authCodesDisabled \|\| Platform.isFuchsia);

	Future<void> startup() async {
	if (running) {
	// Already running.
	return;
	}

	{
	final startingCompleter = _startingCompleter;
	if (startingCompleter != null) {
	if (!startingCompleter.isCompleted) {
	await startingCompleter.future;
	}
	return;
	}
	}

	final startingCompleter = Completer<bool>();
	_startingCompleter = startingCompleter;
	// Startup HTTP server.
	Future<bool> startServer() async {
	try {
	var address;
	var addresses = await InternetAddress.lookup(_ip);
	// Prefer IPv4 addresses.
	for (int i = 0; i < addresses.length; i++) {
	address = addresses[i];
	if (address.type == InternetAddressType.IPv4) break;
	}
	_httpServer = await HttpServer.bind(address, _port);
	} catch (e, st) {
	if (_port != 0 && _enableServicePortFallback) {
	serverPrint(
	'Failed to bind Dart VM service HTTP server to port $_port. '
	'Falling back to automatic port selection',
	);
	_port = 0;
	return await startServer();
	} else {
	serverPrint(
	'Could not start Dart VM service HTTP server:\n'
	'$e\n$st',
	);
	_notifyServerState('');
	onServerAddressChange(null);
	return false;
	}
	}
	return true;
	}

	if (!(await startServer())) {
	startingCompleter.complete(true);
	return;
	}
	if (_service.isExiting) {
	serverPrint(
	'Dart VM service HTTP server exiting before listening as '
	'vm service has received exit request\n',
	);
	startingCompleter.complete(true);
	await shutdown(true);
	return;
	}
	final server = _httpServer!;
	server.listen(_requestHandler, cancelOnError: true);

	if (_waitForDdsToAdvertiseService) {
	_ddsInstance = _DebuggingSession();
	await _ddsInstance!.start(
	serverAddress!,
	_ddsIP,
	_ddsPort.toString(),
	_authCodesDisabled,
	_serveDevtools,
	);
	} else {
	await outputConnectionInformation();
	}
	// Server is up and running.
	_running = true;
	_notifyServerState(serverAddress.toString());
	onServerAddressChange('$serverAddress');
	startingCompleter.complete(true);
	}

	Future<void> shutdown(bool forced) async {
	// If start is pending, wait for it to complete.
	if (_startingCompleter != null) {
	if (!_startingCompleter!.isCompleted) {
	await _startingCompleter!.future;
	}
	}

	final server = _httpServer;
	if (server == null) {
	// Not started.
	return;
	}

	if (Platform.isFuchsia) {
	_cleanupFuchsiaState(server.port);
	}

	final address = serverAddress!;

	try {
	// Shutdown HTTP server and subscription.
	await server.close(force: forced);
	if (!_service.isExiting) {
	// Only print this message if the service has been toggled off, not
	// when the VM is exiting.
	serverPrint('Dart VM service no longer listening on $address');
	}
	} catch (e, st) {
	serverPrint('Could not shutdown Dart VM service HTTP server:\n$e\n$st\n');
	} finally {
	_ddsInstance?.shutdown();
	_ddsInstance = null;
	_httpServer = null;
	_startingCompleter = null;
	_running = false;
	_notifyServerState('');
	onServerAddressChange(null);
	}
	}

	Future<void> outputConnectionInformation() async {
	serverPrint('The Dart VM service is listening on $serverAddress');
	if (Platform.isFuchsia) {
	_writeFuchsiaState(_httpServer!.port);
	}
	final serviceInfoFilenameLocal = _serviceInfoFilename;
	if (serviceInfoFilenameLocal != null &&
	serviceInfoFilenameLocal.isNotEmpty) {
	await _dumpServiceInfoToFile(serviceInfoFilenameLocal);
	}
	}

	bool _isAllowedOrigin(String origin) {
	Uri uri;
	try {
	uri = Uri.parse(origin);
	} catch (_) {
	return false;
	}

	// Explicitly add localhost and 127.0.0.1 on any port (necessary for
	// adb port forwarding).
	if ((uri.host == 'localhost') \|\|
	(uri.host == '::1') \|\|
	(uri.host == '127.0.0.1')) {
	return true;
	}

	final server = _httpServer!;
	if ((uri.port == server.port) &&
	((uri.host == server.address.address) \|\|
	(uri.host == server.address.host))) {
	return true;
	}

	return false;
	}

	bool _originCheck(HttpRequest request) {
	if (_originCheckDisabled) {
	// Always allow.
	return true;
	}
	// First check the web-socket specific origin.
	List<String>? origins = request.headers['Sec-WebSocket-Origin'];
	if (origins == null) {
	// Fall back to the general Origin field.
	origins = request.headers['Origin'];
	}
	if (origins == null) {
	// No origin sent. This is a non-browser client or a same-origin request.
	return true;
	}
	for (final origin in origins) {
	if (_isAllowedOrigin(origin)) {
	return true;
	}
	}
	return false;
	}

	/// Checks the [requestUri] for the service auth token and returns the path
	/// as a String. If the service auth token check fails, returns null.
	/// Returns a Uri if a redirect is required.
	dynamic _checkAuthTokenAndGetPath(Uri requestUri) {
	if (_authCodesDisabled) {
	return requestUri.path == '/' ? ROOT_REDIRECT_PATH : requestUri.path;
	}
	final List<String> requestPathSegments = requestUri.pathSegments;
	if (requestPathSegments.isEmpty) {
	// Malformed.
	return null;
	}
	// Check that we were given the auth token.
	final authToken = requestPathSegments[0];
	if (authToken != serviceAuthToken) {
	// Malformed.
	return null;
	}
	// Missing a trailing '/'. We'll need to redirect to serve
	// ROOT_REDIRECT_PATH correctly, otherwise the response is misinterpreted.
	if (requestPathSegments.length == 1) {
	// requestPathSegments is unmodifiable. Copy it.
	final pathSegments = List<String>.from(requestPathSegments);

	// Adding an empty string to the path segments results in the path having
	// a trailing '/'.
	pathSegments.add('');

	return requestUri.replace(pathSegments: pathSegments);
	}
	// Construct the actual request path by chopping off the auth token.
	return (requestPathSegments[1] == '')
	? ROOT_REDIRECT_PATH
	: '/${requestPathSegments.sublist(1).join('/')}';
	}

	Future<void> _processDevFSRequest(HttpRequest request) async {
	String? fsName;
	String? fsPath;
	Uri? fsUri;

	try {
	// Extract the fs name and fs path from the request headers.
	fsName = request.headers['dev_fs_name']![0];

	// Prefer Uri encoding first, then fallback to path encoding.
	if (request.headers['dev_fs_uri_b64'] case [String base64Uri]) {
	fsUri = Uri.parse(utf8.decode(base64.decode(base64Uri)));
	} else if (request.headers['dev_fs_path_b64'] case [String base64Uri]) {
	fsPath = utf8.decode(base64.decode(base64Uri));
	} else if (request.headers['dev_fs_path'] case [String path]) {
	fsPath = path;
	}
	} catch (_) {
	/* ignore */
	}

	try {
	final result = await _service.devfs.handlePutStream(
	fsName,
	fsPath,
	fsUri,
	request.cast<List<int>>().transform(gzip.decoder),
	);

	request.response.headers.contentType = HttpRequestClient.jsonContentType;
	request.response.write(result);
	} catch (e, st) {
	request.response.statusCode = HttpStatus.internalServerError;
	request.response.write(e);
	} finally {
	request.response.close();
	}
	}

	void _handleWebSocketRequest(HttpRequest request) {
	final subprotocols = request.headers['sec-websocket-protocol'];
	if (acceptNewWebSocketConnections) {
	WebSocketTransformer.upgrade(
	request,
	protocolSelector: subprotocols == null
	? null
	: (_) => 'implicit-redirect',
	compression: CompressionOptions.compressionOff,
	).then((WebSocket webSocket) {
	WebSocketClient(webSocket, _service);
	});
	} else {
	// Attempt to redirect client to the DDS instance.
	request.response.redirect(_service.ddsUri!);
	}
	}

	Future<void> _redirectToDevTools(HttpRequest request) async {
	final ddsUri = _service.ddsUri;
	if (ddsUri == null) {
	request.response.headers.contentType = ContentType.text;
	request.response.write(
	'This VM does not have a registered Dart '
	'Development Service (DDS) instance and is not currently serving '
	'Dart DevTools.',
	);
	request.response.close();
	return;
	}
	// We build this path manually rather than manipulating ddsUri directly
	// as the resulting path requires an unencoded '#'. The Uri class will
	// always encode '#' as '%23' in paths to avoid conflicts with fragments,
	// which will result in the redirect failing.
	final path = StringBuffer();
	// Add authentication code to the path.
	if (ddsUri.pathSegments.length > 1) {
	path.writeAll([
	ddsUri.pathSegments
	.sublist(0, ddsUri.pathSegments.length - 1)
	.join('/'),
	'/',
	]);
	}
	final queryComponent = Uri.encodeQueryComponent(
	ddsUri.replace(scheme: 'ws', path: '${path}ws').toString(),
	);
	path.writeAll(['devtools/', '?uri=$queryComponent']);
	final redirectUri = Uri.parse('http://${ddsUri.host}:${ddsUri.port}/$path');
	request.response.redirect(redirectUri);
	return;
	}

	Future<void> _requestHandler(HttpRequest request) async {
	if (!_originCheck(request)) {
	// This is a cross origin attempt to connect
	request.response.statusCode = HttpStatus.forbidden;
	request.response.write('forbidden origin');
	request.response.close();
	return;
	}
	if (request.method == 'PUT') {
	// PUT requests are forwarded to DevFS for processing.
	await _processDevFSRequest(request);
	return;
	}
	if (request.method != 'GET') {
	// Not a GET request. Do nothing.
	request.response.statusCode = HttpStatus.methodNotAllowed;
	request.response.write('method not allowed');
	request.response.close();
	return;
	}

	final result = _checkAuthTokenAndGetPath(request.uri);
	if (result == null) {
	// Either no authentication code was provided when one was expected or an
	// incorrect authentication code was provided.
	request.response.statusCode = HttpStatus.forbidden;
	request.response.write('missing or invalid authentication code');
	request.response.close();
	return;
	} else if (result is Uri) {
	// The URI contains the valid auth token but is missing a trailing '/'.
	// Redirect to the same URI with the trailing '/' to correctly serve
	// index.html.
	request.response.redirect(result);
	return;
	}

	final String path = result;
	if (path == WEBSOCKET_PATH) {
	_handleWebSocketRequest(request);
	return;
	}
	// Don't redirect HTTP VM service requests, just requests for DevTools
	// assets.
	if (path == ROOT_REDIRECT_PATH) {
	await _redirectToDevTools(request);
	return;
	}
	// HTTP based service request.
	final client = HttpRequestClient(request, _service);
	final message = Message.fromUri(
	client,
	Uri(path: path, queryParameters: request.uri.queryParameters),
	);
	client.onRequest(message); // exception free, no need to try catch
	}

	Future<File> _dumpServiceInfoToFile(String serviceInfoFilenameLocal) async {
	final serviceInfo = <String, dynamic>{'uri': serverAddress.toString()};
	const kFileScheme = 'file://';
	// There's lots of URI parsing weirdness as Uri.parse doesn't do the right
	// thing with Windows drive letters. Only use Uri.parse with known file
	// URIs, and use Uri.file otherwise to properly handle drive letters in
	// paths.
	final uri = serviceInfoFilenameLocal.startsWith(kFileScheme)
	? Uri.parse(serviceInfoFilenameLocal)
	: Uri.file(serviceInfoFilenameLocal);
	final file = File.fromUri(uri);
	return file.writeAsString(json.encode(serviceInfo));
	}

	void _writeFuchsiaState(int port) {
	// Create a file with the port number.
	final tmp = Directory.systemTemp.path;
	final path = '$tmp/dart.services/${port}';
	serverPrint('Creating $path');
	File(path).createSync(recursive: true);
	}

	void _cleanupFuchsiaState(int port) {
	// Remove the file with the port number.
	final tmp = Directory.systemTemp.path;
	final path = '$tmp/dart.services/$port';
	serverPrint('Deleting $path');
	File(path).deleteSync();
	}
	}

	@pragma("vm:external-name", "VMServiceIO_NotifyServerState")
	external void _notifyServerState(String uri);