Revert "Remove race conditions involving finding available ports (#18488)" (#18521)

This reverts commit 77508722.

dev/devicelab/bin/tasks/commands_test.dart

@@ -35,14 +35,12 @@ void main() {
         .listen((String line) {
           print('run:stdout: $line');
           stdout.add(line);
-          if (vmServicePort == null) {
+          if (lineContainsServicePort(line)) {
             vmServicePort = parseServicePort(line);
-            if (vmServicePort != null) {
-              print('service protocol connection available at port $vmServicePort');
-              print('run: ready!');
-              ready.complete();
-              ok ??= true;
-            }
+            print('service protocol connection available at port $vmServicePort');
+            print('run: ready!');
+            ready.complete();
+            ok ??= true;
           }
         });
       run.stderr

dev/devicelab/bin/tasks/routing_test.dart

@@ -41,14 +41,12 @@ void main() {
         .transform(const LineSplitter())
         .listen((String line) {
           print('run:stdout: $line');
-          if (vmServicePort == null) {
+          if (lineContainsServicePort(line)) {
             vmServicePort = parseServicePort(line);
-            if (vmServicePort != null) {
-              print('service protocol connection available at port $vmServicePort');
-              print('run: ready!');
-              ready.complete();
-              ok ??= true;
-            }
+            print('service protocol connection available at port $vmServicePort');
+            print('run: ready!');
+            ready.complete();
+            ok ??= true;
           }
         });
       run.stderr

dev/devicelab/bin/tasks/service_extensions_test.dart

@@ -33,14 +33,12 @@ void main() {
           .transform(const LineSplitter())
           .listen((String line) {
         print('run:stdout: $line');
-        if (vmServicePort == null) {
+        if (lineContainsServicePort(line)) {
           vmServicePort = parseServicePort(line);
-          if (vmServicePort != null) {
-            print('service protocol connection available at port $vmServicePort');
-            print('run: ready!');
-            ready.complete();
-            ok ??= true;
-          }
+          print('service protocol connection available at port $vmServicePort');
+          print('run: ready!');
+          ready.complete();
+          ok ??= true;
         }
       });
       run.stderr

dev/devicelab/lib/framework/runner.dart

@@ -28,8 +28,9 @@ Future<Map<String, dynamic>> runTask(String taskName, { bool silent = false }) a
   if (!file(taskExecutable).existsSync())
     throw 'Executable Dart file not found: $taskExecutable';
 
+  final int vmServicePort = await findAvailablePort();
   final Process runner = await startProcess(dartBin, <String>[
-    '--enable-vm-service=0',
+    '--enable-vm-service=$vmServicePort',
     '--no-pause-isolates-on-exit',
     taskExecutable,
   ]);
@@ -40,17 +41,10 @@ Future<Map<String, dynamic>> runTask(String taskName, { bool silent = false }) a
     runnerFinished = true;
   });
 
-  final Completer<int> port = new Completer<int>();
-
   final StreamSubscription<String> stdoutSub = runner.stdout
       .transform(const Utf8Decoder())
       .transform(const LineSplitter())
       .listen((String line) {
-    if (!port.isCompleted) {
-      final int portValue = parseServicePort(line, prefix: 'Observatory listening on ');
-      if (portValue != null)
-        port.complete(portValue);
-    }
     if (!silent) {
       stdout.writeln('[$taskName] [STDOUT] $line');
     }
@@ -65,7 +59,7 @@ Future<Map<String, dynamic>> runTask(String taskName, { bool silent = false }) a
 
   String waitingFor = 'connection';
   try {
-    final VMIsolateRef isolate = await _connectToRunnerIsolate(await port.future);
+    final VMIsolateRef isolate = await _connectToRunnerIsolate(vmServicePort);
     waitingFor = 'task completion';
     final Map<String, dynamic> taskResult =
         await isolate.invokeExtension('ext.cocoonRunTask').timeout(taskTimeoutWithGracePeriod);

dev/devicelab/lib/framework/utils.dart

@@ -480,6 +480,21 @@ Future<Null> runAndCaptureAsyncStacks(Future<Null> callback()) {
   return completer.future;
 }
 
+/// Return an unused TCP port number.
+Future<int> findAvailablePort() async {
+  int port = 20000;
+  while (true) {
+    try {
+      final ServerSocket socket =
+          await ServerSocket.bind(InternetAddress.LOOPBACK_IP_V4, port); // ignore: deprecated_member_use
+      await socket.close();
+      return port;
+    } catch (_) {
+      port++;
+    }
+  }
+}
+
 bool canRun(String path) => _processManager.canRun(path);
 
 String extractCloudAuthTokenArg(List<String> rawArgs) {
@@ -502,20 +517,13 @@ String extractCloudAuthTokenArg(List<String> rawArgs) {
   return token;
 }
 
-/// Tries to extract a port from the string.
-///
-/// The `prefix`, if specified, is a regular expression pattern and must not contain groups.
-///
-/// The `multiLine` flag should be set to true if `line` is actually a buffer of many lines.
-int parseServicePort(String line, {
-  String prefix = 'An Observatory debugger .* is available at: ',
-  bool multiLine = false,
-}) {
-  // e.g. "An Observatory debugger and profiler on ... is available at: http://127.0.0.1:8100/"
-  final RegExp pattern = new RegExp('$prefix(\\S+:(\\d+)/\\S*)\$', multiLine: multiLine);
-  final Match match = pattern.firstMatch(line);
-  print(pattern);
-  print(match);
+// "An Observatory debugger and profiler on ... is available at: http://127.0.0.1:8100/"
+final RegExp _kObservatoryRegExp = new RegExp(r'An Observatory debugger .* is available at: (\S+:(\d+))');
+
+bool lineContainsServicePort(String line) => line.contains(_kObservatoryRegExp);
+
+int parseServicePort(String line) {
+  final Match match = _kObservatoryRegExp.firstMatch(line);
   return match == null ? null : int.parse(match.group(2));
 }
 

dev/devicelab/lib/tasks/perf_tests.dart

@@ -364,6 +364,8 @@ class MemoryTest {
       if (deviceOperatingSystem == DeviceOperatingSystem.ios)
         await prepareProvisioningCertificates(testDirectory);
 
+      final int observatoryPort = await findAvailablePort();
+
       final List<String> runOptions = <String>[
         '-v',
         '--profile',
@@ -371,14 +373,11 @@ class MemoryTest {
         '-d',
         deviceId,
         '--observatory-port',
-        '0',
+        observatoryPort.toString(),
       ];
       if (testTarget != null)
         runOptions.addAll(<String>['-t', testTarget]);
-      final String output = await evalFlutter('run', options: runOptions);
-      final int observatoryPort = parseServicePort(output, prefix: 'Successfully connected to service protocol: ', multiLine: true);
-      if (observatoryPort == null)
-        throw new Exception('Could not find observatory port in "flutter run" output.');
+      await flutter('run', options: runOptions);
 
       final Map<String, dynamic> startData = await device.getMemoryStats(packageName);
 

packages/flutter_tools/lib/src/android/android_device.dart

@@ -15,6 +15,7 @@ import '../base/common.dart' show throwToolExit;
 import '../base/file_system.dart';
 import '../base/io.dart';
 import '../base/logger.dart';
+import '../base/port_scanner.dart';
 import '../base/process.dart';
 import '../base/process_manager.dart';
 import '../base/utils.dart';
@@ -843,7 +844,7 @@ class _AndroidDevicePortForwarder extends DevicePortForwarder {
         final int devicePort = _extractPort(splitLine[2]);
 
         // Failed, skip.
-        if (hostPort == null || devicePort == null)
+        if ((hostPort == null) || (devicePort == null))
           continue;
 
         ports.add(new ForwardedPort(hostPort, devicePort));
@@ -854,29 +855,15 @@ class _AndroidDevicePortForwarder extends DevicePortForwarder {
   }
 
   @override
-  Future<int> forward(int devicePort, {int hostPort}) async {
-    hostPort ??= 0;
-    final RunResult process = await runCheckedAsync(device.adbCommandForDevice(
-      <String>['forward', 'tcp:$hostPort', 'tcp:$devicePort']
-    ));
-
-    if (process.stderr.isNotEmpty)
-      process.throwException('adb returned error:\n${process.stderr}');
-
-    if (process.exitCode != 0) {
-      if (process.stdout.isNotEmpty)
-        process.throwException('adb returned error:\n${process.stdout}');
-      process.throwException('adb failed without a message');
+  Future<int> forward(int devicePort, { int hostPort }) async {
+    if ((hostPort == null) || (hostPort == 0)) {
+      // Auto select host port.
+      hostPort = await portScanner.findAvailablePort();
     }
 
-    if (hostPort == 0) {
-      if (process.stdout.isEmpty)
-        process.throwException('adb did not report forwarded port');
-      hostPort = int.tryParse(process.stdout) ?? (throw 'adb returned invalid port number:\n${process.stdout}');
-    } else {
-      if (process.stdout.isNotEmpty)
-        process.throwException('adb returned error:\n${process.stdout}');
-    }
+    await runCheckedAsync(device.adbCommandForDevice(
+      <String>['forward', 'tcp:$hostPort', 'tcp:$devicePort']
+    ));
 
     return hostPort;
   }

packages/flutter_tools/lib/src/base/common.dart

@@ -5,6 +5,8 @@
 import 'file_system.dart';
 import 'platform.dart';
 
+const int kDefaultObservatoryPort = 8100;
+
 /// Return the absolute path of the user's home directory
 String get homeDirPath {
   if (_homeDirPath == null) {

packages/flutter_tools/lib/src/base/port_scanner.dart

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:async';
+
+import 'context.dart';
+import 'io.dart';
+
+const int _kMaxSearchIterations = 20;
+
+PortScanner get portScanner => context[PortScanner];
+
+abstract class PortScanner {
+  const PortScanner();
+
+  /// Returns true if the specified [port] is available to bind to.
+  Future<bool> isPortAvailable(int port);
+
+  /// Returns an available ephemeral port.
+  Future<int> findAvailablePort();
+
+  /// Returns an available port as close to [defaultPort] as possible.
+  ///
+  /// If [defaultPort] is available, this will return it. Otherwise, it will
+  /// search for an available port close to [defaultPort]. If it cannot find one,
+  /// it will return any available port.
+  Future<int> findPreferredPort(int defaultPort) async {
+    int iterationCount = 0;
+
+    while (iterationCount < _kMaxSearchIterations) {
+      final int port = defaultPort + iterationCount;
+      if (await isPortAvailable(port))
+        return port;
+      iterationCount++;
+    }
+
+    return findAvailablePort();
+  }
+}
+
+class HostPortScanner extends PortScanner {
+  const HostPortScanner();
+
+  @override
+  Future<bool> isPortAvailable(int port) async {
+    try {
+      // TODO(ianh): This is super racy.
+      final ServerSocket socket = await ServerSocket.bind(InternetAddress.LOOPBACK_IP_V4, port); // ignore: deprecated_member_use
+      await socket.close();
+      return true;
+    } catch (error) {
+      return false;
+    }
+  }
+
+  @override
+  Future<int> findAvailablePort() async {
+    ServerSocket socket;
+    try {
+      socket = await ServerSocket.bind(InternetAddress.LOOPBACK_IP_V4, 0); // ignore: deprecated_member_use
+    } on SocketException {
+      socket = await ServerSocket.bind(InternetAddress.LOOPBACK_IP_V6, 0, v6Only: true); // ignore: deprecated_member_use
+    }
+    final int port = socket.port;
+    await socket.close();
+    return port;
+  }
+}

packages/flutter_tools/lib/src/base/process.dart

@@ -229,7 +229,7 @@ Future<RunResult> runAsync(List<String> cmd, {
     workingDirectory: workingDirectory,
     environment: _environment(allowReentrantFlutter, environment),
   );
-  final RunResult runResults = new RunResult(results, cmd);
+  final RunResult runResults = new RunResult(results);
   printTrace(runResults.toString());
   return runResults;
 }
@@ -240,10 +240,10 @@ Future<RunResult> runCheckedAsync(List<String> cmd, {
   Map<String, String> environment
 }) async {
   final RunResult result = await runAsync(
-    cmd,
-    workingDirectory: workingDirectory,
-    allowReentrantFlutter: allowReentrantFlutter,
-    environment: environment,
+      cmd,
+      workingDirectory: workingDirectory,
+      allowReentrantFlutter: allowReentrantFlutter,
+      environment: environment
   );
   if (result.exitCode != 0)
     throw 'Exit code ${result.exitCode} from: ${cmd.join(' ')}:\n$result';
@@ -364,12 +364,10 @@ class ProcessExit implements Exception {
 }
 
 class RunResult {
-  RunResult(this.processResult, this._command) : assert(_command != null), assert(_command.isNotEmpty);
+  RunResult(this.processResult);
 
   final ProcessResult processResult;
 
-  final List<String> _command;
-
   int get exitCode => processResult.exitCode;
   String get stdout => processResult.stdout;
   String get stderr => processResult.stderr;
@@ -383,14 +381,4 @@ class RunResult {
       out.writeln(processResult.stderr);
     return out.toString().trimRight();
   }
-
- /// Throws a [ProcessException] with the given `message`.
- void throwException(String message) {
-    throw new ProcessException(
-      _command.first,
-      _command.skip(1).toList(),
-      message,
-      exitCode,
-    );
-  }
 }

packages/flutter_tools/lib/src/commands/run.dart

@@ -55,7 +55,8 @@ abstract class RunCommandBase extends FlutterCommand {
   void usesPortOptions() {
     argParser.addOption('observatory-port',
         help: 'Listen to the given port for an observatory debugger connection.\n'
-              'Specifying port 0 (the default) will find a random free port.'
+              'Specifying port 0 will find a random free port.\n'
+              'Defaults to the first available port after $kDefaultObservatoryPort.'
     );
   }
 

packages/flutter_tools/lib/src/commands/trace.dart

@@ -16,18 +16,14 @@ import '../tracing.dart';
 class TraceCommand extends FlutterCommand {
   TraceCommand() {
     requiresPubspecYaml();
-    argParser.addOption('debug-port',
-      help: 'Local port where the observatory is listening. Required.',
-    );
-    argParser.addFlag('start', negatable: false, help: 'Start tracing. Implied if --stop is also omitted.');
-    argParser.addFlag('stop', negatable: false, help: 'Stop tracing. Implied if --start is also omitted.');
-    argParser.addOption('duration',
-      abbr: 'd',
-      help: 'Time to wait after starting (if --start is specified or implied) and before\n'
-            'stopping (if --stop is specified or implied).\n'
-            'Defaults to ten seconds if --stop is specified or implied, zero otherwise.',
-    );
+    argParser.addFlag('start', negatable: false, help: 'Start tracing.');
+    argParser.addFlag('stop', negatable: false, help: 'Stop tracing.');
     argParser.addOption('out', help: 'Specify the path of the saved trace file.');
+    argParser.addOption('duration',
+        defaultsTo: '10', abbr: 'd', help: 'Duration in seconds to trace.');
+    argParser.addOption('debug-port',
+        defaultsTo: kDefaultObservatoryPort.toString(),
+        help: 'Local port where the observatory is listening.');
   }
 
   @override
@@ -38,39 +34,13 @@ class TraceCommand extends FlutterCommand {
 
   @override
   final String usageFooter =
-    '\`trace\` called without the --start or --stop flags will automatically start tracing,\n'
-    'delay a set amount of time (controlled by --duration), and stop tracing. To explicitly\n'
-    'control tracing, call trace with --start and later with --stop.\n'
-    'The --debug-port argument is required.';
+    '\`trace\` called with no arguments will automatically start tracing, delay a set amount of\n'
+    'time (controlled by --duration), and stop tracing. To explicitly control tracing, call trace\n'
+    'with --start and later with --stop.';
 
   @override
   Future<Null> runCommand() async {
-    int observatoryPort;
-    if (argResults.wasParsed('debug-port')) {
-      observatoryPort = int.tryParse(argResults['debug-port']);
-    }
-    if (observatoryPort == null) {
-      throwToolExit('The --debug-port argument must be specified.');
-    }
-
-    bool start = argResults['start'];
-    bool stop = argResults['stop'];
-    if (!start && !stop) {
-      start = true;
-      stop = true;
-    }
-    assert(start || stop);
-
-    Duration duration;
-    if (argResults.wasParsed('duration')) {
-      try {
-        duration = new Duration(seconds: int.parse(argResults['duration']));
-      } on FormatException {
-        throwToolExit('Invalid duration passed to --duration; it should be a positive number of seconds.');
-      }
-    } else {
-      duration = stop ? const Duration(seconds: 10) : Duration.zero;
-    }
+    final int observatoryPort = int.parse(argResults['debug-port']);
 
     // TODO(danrubel): this will break if we move to the new observatory URL
     // See https://github.com/flutter/flutter/issues/7038
@@ -86,11 +56,20 @@ class TraceCommand extends FlutterCommand {
 
     Cache.releaseLockEarly();
 
-    if (start)
+    if ((!argResults['start'] && !argResults['stop']) ||
+        (argResults['start'] && argResults['stop'])) {
+      // Setting neither flags or both flags means do both commands and wait
+      // duration seconds in between.
       await tracing.startTracing();
-    await new Future<Null>.delayed(duration);
-    if (stop)
+      await new Future<Null>.delayed(
+        new Duration(seconds: int.parse(argResults['duration'])),
+        () => _stopTracing(tracing)
+      );
+    } else if (argResults['stop']) {
       await _stopTracing(tracing);
+    } else {
+      await tracing.startTracing();
+    }
   }
 
   Future<Null> _stopTracing(Tracing tracing) async {

packages/flutter_tools/lib/src/context_runner.dart

@@ -19,6 +19,7 @@ import 'base/io.dart';
 import 'base/logger.dart';
 import 'base/os.dart';
 import 'base/platform.dart';
+import 'base/port_scanner.dart';
 import 'base/utils.dart';
 import 'cache.dart';
 import 'compile.dart';
@@ -69,6 +70,7 @@ Future<T> runInContext<T>(
       KernelCompiler: () => const KernelCompiler(),
       Logger: () => platform.isWindows ? new WindowsStdoutLogger() : new StdoutLogger(),
       OperatingSystemUtils: () => new OperatingSystemUtils(),
+      PortScanner: () => const HostPortScanner(),
       SimControl: () => new SimControl(),
       Stdio: () => const Stdio(),
       Usage: () => new Usage(),

packages/flutter_tools/lib/src/device.dart

@@ -7,8 +7,10 @@ import 'dart:math' as math;
 
 import 'android/android_device.dart';
 import 'application_package.dart';
+import 'base/common.dart';
 import 'base/context.dart';
 import 'base/file_system.dart';
+import 'base/port_scanner.dart';
 import 'base/utils.dart';
 import 'build_info.dart';
 import 'globals.dart';
@@ -365,6 +367,14 @@ class DebuggingOptions {
   final int observatoryPort;
 
   bool get hasObservatoryPort => observatoryPort != null;
+
+  /// Return the user specified observatory port. If that isn't available,
+  /// return [kDefaultObservatoryPort], or a port close to that one.
+  Future<int> findBestObservatoryPort() {
+    if (hasObservatoryPort)
+      return new Future<int>.value(observatoryPort);
+    return portScanner.findPreferredPort(observatoryPort ?? kDefaultObservatoryPort);
+  }
 }
 
 class LaunchResult {
@@ -404,9 +414,9 @@ abstract class DevicePortForwarder {
   List<ForwardedPort> get forwardedPorts;
 
   /// Forward [hostPort] on the host to [devicePort] on the device.
-  /// If [hostPort] is null or zero, will auto select a host port.
+  /// If [hostPort] is null, will auto select a host port.
   /// Returns a Future that completes with the host port.
-  Future<int> forward(int devicePort, {int hostPort});
+  Future<int> forward(int devicePort, { int hostPort });
 
   /// Stops forwarding [forwardedPort].
   Future<Null> unforward(ForwardedPort forwardedPort);

packages/flutter_tools/lib/src/ios/devices.dart

@@ -10,6 +10,7 @@ import '../base/file_system.dart';
 import '../base/io.dart';
 import '../base/logger.dart';
 import '../base/platform.dart';
+import '../base/port_scanner.dart';
 import '../base/process.dart';
 import '../base/process_manager.dart';
 import '../build_info.dart';
@@ -508,40 +509,26 @@ class _IOSDevicePortForwarder extends DevicePortForwarder {
 
   @override
   Future<int> forward(int devicePort, {int hostPort}) async {
-    final bool autoselect = hostPort == null || hostPort == 0;
-    if (autoselect)
-      hostPort = 1024;
-
-    Process process;
-
-    bool connected = false;
-    while (!connected) {
-      // Usage: iproxy LOCAL_TCP_PORT DEVICE_TCP_PORT UDID
-      process = await runCommand(<String>[
-        device._iproxyPath,
-        hostPort.toString(),
-        devicePort.toString(),
-        device.id,
-      ]);
-      connected = !await process.stdout.isEmpty;
-      if (!connected) {
-        if (autoselect) {
-          hostPort += 1;
-          if (hostPort > 65535)
-            throw 'Could not find open port on host.';
-        } else {
-          throw 'Port $hostPort is not available.';
-        }
-      }
+    if ((hostPort == null) || (hostPort == 0)) {
+      // Auto select host port.
+      hostPort = await portScanner.findAvailablePort();
     }
-    assert(connected);
-    assert(process != null);
 
-    final ForwardedPort forwardedPort = new ForwardedPort.withContext(
-      hostPort, devicePort, process,
-    );
+    // Usage: iproxy LOCAL_TCP_PORT DEVICE_TCP_PORT UDID
+    final Process process = await runCommand(<String>[
+      device._iproxyPath,
+      hostPort.toString(),
+      devicePort.toString(),
+      device.id,
+    ]);
+
+    final ForwardedPort forwardedPort = new ForwardedPort.withContext(hostPort,
+        devicePort, process);
+
     printTrace('Forwarded port $forwardedPort');
+
     _forwardedPorts.add(forwardedPort);
+
     return hostPort;
   }
 

packages/flutter_tools/lib/src/ios/simulators.dart

@@ -305,7 +305,8 @@ class IOSSimulator extends Device {
         args.add('--skia-deterministic-rendering');
       if (debuggingOptions.useTestFonts)
         args.add('--use-test-fonts');
-      final int observatoryPort = debuggingOptions.observatoryPort ?? 0;
+
+      final int observatoryPort = await debuggingOptions.findBestObservatoryPort();
       args.add('--observatory-port=$observatoryPort');
     }
 
@@ -692,7 +693,7 @@ class _IOSSimulatorDevicePortForwarder extends DevicePortForwarder {
 
   @override
   Future<int> forward(int devicePort, {int hostPort}) async {
-    if (hostPort == null || hostPort == 0) {
+    if ((hostPort == null) || (hostPort == 0)) {
       hostPort = devicePort;
     }
     assert(devicePort == hostPort);

packages/flutter_tools/lib/src/protocol_discovery.dart

@@ -4,7 +4,9 @@
 
 import 'dart:async';
 
+import 'base/common.dart';
 import 'base/io.dart';
+import 'base/port_scanner.dart';
 import 'device.dart';
 import 'globals.dart';
 
@@ -16,8 +18,10 @@ class ProtocolDiscovery {
     this.serviceName, {
     this.portForwarder,
     this.hostPort,
+    this.defaultHostPort,
     this.ipv6,
   }) : assert(logReader != null),
+       assert(portForwarder == null || defaultHostPort != null),
        _prefix = '$serviceName listening on ' {
     _deviceLogSubscription = logReader.logLines.listen(_handleLine);
   }
@@ -33,6 +37,7 @@ class ProtocolDiscovery {
       logReader, kObservatoryService,
       portForwarder: portForwarder,
       hostPort: hostPort,
+      defaultHostPort: kDefaultObservatoryPort,
       ipv6: ipv6,
     );
   }
@@ -41,6 +46,7 @@ class ProtocolDiscovery {
   final String serviceName;
   final DevicePortForwarder portForwarder;
   final int hostPort;
+  final int defaultHostPort;
   final bool ipv6;
 
   final String _prefix;
@@ -82,15 +88,16 @@ class ProtocolDiscovery {
     Uri hostUri = deviceUri;
 
     if (portForwarder != null) {
-      final int actualDevicePort = deviceUri.port;
-      final int actualHostPort = await portForwarder.forward(actualDevicePort, hostPort: hostPort);
-      printTrace('Forwarded host port $actualHostPort to device port $actualDevicePort for $serviceName');
-      hostUri = deviceUri.replace(port: actualHostPort);
+      final int devicePort = deviceUri.port;
+      int hostPort = this.hostPort ?? await portScanner.findPreferredPort(defaultHostPort);
+      hostPort = await portForwarder.forward(devicePort, hostPort: hostPort);
+      printTrace('Forwarded host port $hostPort to device port $devicePort for $serviceName');
+      hostUri = deviceUri.replace(port: hostPort);
     }
 
     assert(new InternetAddress(hostUri.host).isLoopback);
     if (ipv6) {
-      hostUri = hostUri.replace(host: InternetAddress.loopbackIPv6.host);
+      hostUri = hostUri.replace(host: InternetAddress.LOOPBACK_IP_V6.host); // ignore: deprecated_member_use
     }
 
     return hostUri;

packages/flutter_tools/lib/src/tester/flutter_tester.dart

@@ -122,7 +122,8 @@ class FlutterTesterDevice extends Device {
         command.add('--start-paused');
       }
       if (debuggingOptions.hasObservatoryPort)
-        command.add('--observatory-port=${debuggingOptions.observatoryPort}');
+        command
+            .add('--observatory-port=${debuggingOptions.hasObservatoryPort}');
     }
 
     // Build assets and perform initial compilation.
@@ -169,10 +170,9 @@ class FlutterTesterDevice extends Device {
       if (!debuggingOptions.debuggingEnabled)
         return new LaunchResult.succeeded();
 
-      final ProtocolDiscovery observatoryDiscovery = new ProtocolDiscovery.observatory(
-        getLogReader(),
-        hostPort: debuggingOptions.observatoryPort,
-      );
+      final ProtocolDiscovery observatoryDiscovery =
+          new ProtocolDiscovery.observatory(getLogReader(),
+              hostPort: debuggingOptions.observatoryPort);
 
       final Uri observatoryUri = await observatoryDiscovery.uri;
       return new LaunchResult.succeeded(observatoryUri: observatoryUri);

packages/flutter_tools/test/base/build_test.dart

@@ -381,7 +381,7 @@ void main() {
         fs.path.join(outputPath, 'snapshot.d'): '${fs.path.join(outputPath, 'snapshot_assembly.S')} : ',
       };
 
-      final RunResult successResult = new RunResult(new ProcessResult(1, 0, '', ''), <String>['command name', 'arguments...']);
+      final RunResult successResult = new RunResult(new ProcessResult(1, 0, '', ''));
       when(xcode.cc(any)).thenAnswer((_) => new Future<RunResult>.value(successResult));
       when(xcode.clang(any)).thenAnswer((_) => new Future<RunResult>.value(successResult));
 
@@ -428,7 +428,7 @@ void main() {
         fs.path.join(outputPath, 'snapshot.d'): '${fs.path.join(outputPath, 'snapshot_assembly.S')} : ',
       };
 
-      final RunResult successResult = new RunResult(new ProcessResult(1, 0, '', ''), <String>['command name', 'arguments...']);
+      final RunResult successResult = new RunResult(new ProcessResult(1, 0, '', ''));
       when(xcode.cc(any)).thenAnswer((_) => new Future<RunResult>.value(successResult));
       when(xcode.clang(any)).thenAnswer((_) => new Future<RunResult>.value(successResult));
 
@@ -476,7 +476,7 @@ void main() {
         fs.path.join(outputPath, 'snapshot.d'): '${fs.path.join(outputPath, 'vm_snapshot_data')} : ',
       };
 
-      final RunResult successResult = new RunResult(new ProcessResult(1, 0, '', ''), <String>['command name', 'arguments...']);
+      final RunResult successResult = new RunResult(new ProcessResult(1, 0, '', ''));
       when(xcode.cc(any)).thenAnswer((_) => new Future<RunResult>.value(successResult));
       when(xcode.clang(any)).thenAnswer((_) => new Future<RunResult>.value(successResult));
 
@@ -528,7 +528,7 @@ void main() {
         fs.path.join(outputPath, 'snapshot.d'): '${fs.path.join(outputPath, 'vm_snapshot_data')} : ',
       };
 
-      final RunResult successResult = new RunResult(new ProcessResult(1, 0, '', ''), <String>['command name', 'arguments...']);
+      final RunResult successResult = new RunResult(new ProcessResult(1, 0, '', ''));
       when(xcode.cc(any)).thenAnswer((_) => new Future<RunResult>.value(successResult));
       when(xcode.clang(any)).thenAnswer((_) => new Future<RunResult>.value(successResult));
 
@@ -575,7 +575,7 @@ void main() {
         fs.path.join(outputPath, 'snapshot.d'): '${fs.path.join(outputPath, 'snapshot_assembly.S')} : ',
       };
 
-      final RunResult successResult = new RunResult(new ProcessResult(1, 0, '', ''), <String>['command name', 'arguments...']);
+      final RunResult successResult = new RunResult(new ProcessResult(1, 0, '', ''));
       when(xcode.cc(any)).thenAnswer((_) => new Future<RunResult>.value(successResult));
       when(xcode.clang(any)).thenAnswer((_) => new Future<RunResult>.value(successResult));
 
@@ -622,7 +622,7 @@ void main() {
         fs.path.join(outputPath, 'snapshot.d'): '${fs.path.join(outputPath, 'snapshot_assembly.S')} : ',
       };
 
-      final RunResult successResult = new RunResult(new ProcessResult(1, 0, '', ''), <String>['command name', 'arguments...']);
+      final RunResult successResult = new RunResult(new ProcessResult(1, 0, '', ''));
       when(xcode.cc(any)).thenAnswer((_) => new Future<RunResult>.value(successResult));
       when(xcode.clang(any)).thenAnswer((_) => new Future<RunResult>.value(successResult));
 
@@ -689,7 +689,7 @@ void main() {
         fs.path.join(outputPath, 'snapshot.d'): '${fs.path.join(outputPath, 'vm_snapshot_data')} : ',
       };
 
-      final RunResult successResult = new RunResult(new ProcessResult(1, 0, '', ''), <String>['command name', 'arguments...']);
+      final RunResult successResult = new RunResult(new ProcessResult(1, 0, '', ''));
       when(xcode.cc(any)).thenAnswer((_) => new Future<RunResult>.value(successResult));
       when(xcode.clang(any)).thenAnswer((_) => new Future<RunResult>.value(successResult));
 
@@ -741,7 +741,7 @@ void main() {
         fs.path.join(outputPath, 'snapshot.d'): '${fs.path.join(outputPath, 'vm_snapshot_data')} : ',
       };
 
-      final RunResult successResult = new RunResult(new ProcessResult(1, 0, '', ''), <String>['command name', 'arguments...']);
+      final RunResult successResult = new RunResult(new ProcessResult(1, 0, '', ''));
       when(xcode.cc(any)).thenAnswer((_) => new Future<RunResult>.value(successResult));
       when(xcode.clang(any)).thenAnswer((_) => new Future<RunResult>.value(successResult));
 

packages/flutter_tools/test/protocol_discovery_test.dart

@@ -115,16 +115,16 @@ void main() {
       testUsingContext('default port', () async {
         final MockDeviceLogReader logReader = new MockDeviceLogReader();
         final ProtocolDiscovery discoverer = new ProtocolDiscovery.observatory(
-          logReader,
-          portForwarder: new MockPortForwarder(99),
-        );
+            logReader,
+            portForwarder: new MockPortForwarder(99),
+            hostPort: 54777);
 
         // Get next port future.
         final Future<Uri> nextUri = discoverer.uri;
         logReader.addLine('I/flutter : Observatory listening on http://127.0.0.1:54804/PTwjm8Ii8qg=/');
         final Uri uri = await nextUri;
-        expect(uri.port, 99);
-        expect('$uri', 'http://127.0.0.1:99/PTwjm8Ii8qg=/');
+        expect(uri.port, 54777);
+        expect('$uri', 'http://127.0.0.1:54777/PTwjm8Ii8qg=/');
 
         discoverer.cancel();
         logReader.dispose();
@@ -133,10 +133,9 @@ void main() {
       testUsingContext('specified port', () async {
         final MockDeviceLogReader logReader = new MockDeviceLogReader();
         final ProtocolDiscovery discoverer = new ProtocolDiscovery.observatory(
-          logReader,
-          portForwarder: new MockPortForwarder(99),
-          hostPort: 1243,
-        );
+            logReader,
+            portForwarder: new MockPortForwarder(99),
+            hostPort: 1243);
 
         // Get next port future.
         final Future<Uri> nextUri = discoverer.uri;
@@ -149,33 +148,13 @@ void main() {
         logReader.dispose();
       });
 
-      testUsingContext('specified port zero', () async {
-        final MockDeviceLogReader logReader = new MockDeviceLogReader();
-        final ProtocolDiscovery discoverer = new ProtocolDiscovery.observatory(
-          logReader,
-          portForwarder: new MockPortForwarder(99),
-          hostPort: 0,
-        );
-
-        // Get next port future.
-        final Future<Uri> nextUri = discoverer.uri;
-        logReader.addLine('I/flutter : Observatory listening on http://127.0.0.1:54804/PTwjm8Ii8qg=/');
-        final Uri uri = await nextUri;
-        expect(uri.port, 99);
-        expect('$uri', 'http://127.0.0.1:99/PTwjm8Ii8qg=/');
-
-        discoverer.cancel();
-        logReader.dispose();
-      });
-
       testUsingContext('ipv6', () async {
         final MockDeviceLogReader logReader = new MockDeviceLogReader();
         final ProtocolDiscovery discoverer = new ProtocolDiscovery.observatory(
-          logReader,
-          portForwarder: new MockPortForwarder(99),
-          hostPort: 54777,
-          ipv6: true,
-        );
+            logReader,
+            portForwarder: new MockPortForwarder(99),
+            hostPort: 54777,
+            ipv6: true);
 
         // Get next port future.
         final Future<Uri> nextUri = discoverer.uri;
@@ -196,12 +175,7 @@ class MockPortForwarder extends DevicePortForwarder {
   MockPortForwarder([this.availablePort]);
 
   @override
-  Future<int> forward(int devicePort, {int hostPort}) async {
-    hostPort ??= 0;
-    if (hostPort == 0)
-      return availablePort;
-    return hostPort;
-  }
+  Future<int> forward(int devicePort, {int hostPort}) async => hostPort ?? availablePort;
 
   @override
   List<ForwardedPort> get forwardedPorts => throw 'not implemented';

packages/flutter_tools/test/src/context.dart

@@ -12,6 +12,7 @@ import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/base/io.dart';
 import 'package:flutter_tools/src/base/logger.dart';
 import 'package:flutter_tools/src/base/os.dart';
+import 'package:flutter_tools/src/base/port_scanner.dart';
 import 'package:flutter_tools/src/cache.dart';
 import 'package:flutter_tools/src/context_runner.dart';
 import 'package:flutter_tools/src/device.dart';
@@ -76,6 +77,7 @@ void testUsingContext(String description, dynamic testMethod(), {
           },
           Logger: () => new BufferLogger(),
           OperatingSystemUtils: () => new MockOperatingSystemUtils(),
+          PortScanner: () => new MockPortScanner(),
           SimControl: () => new MockSimControl(),
           Usage: () => new MockUsage(),
           XcodeProjectInterpreter: () => new MockXcodeProjectInterpreter(),
@@ -125,6 +127,16 @@ void _printBufferedErrors(AppContext testContext) {
   }
 }
 
+class MockPortScanner extends PortScanner {
+  static int _nextAvailablePort = 12345;
+
+  @override
+  Future<bool> isPortAvailable(int port) async => true;
+
+  @override
+  Future<int> findAvailablePort() async => _nextAvailablePort++;
+}
+
 class MockDeviceManager implements DeviceManager {
   List<Device> devices = <Device>[];
 

packages/flutter_tools/test/vmservice_test.dart

@@ -4,6 +4,7 @@
 
 import 'package:test/test.dart';
 
+import 'package:flutter_tools/src/base/port_scanner.dart';
 import 'package:flutter_tools/src/vmservice.dart';
 
 import 'src/common.dart';
@@ -12,8 +13,9 @@ import 'src/context.dart';
 void main() {
   group('VMService', () {
     testUsingContext('fails connection eagerly in the connect() method', () async {
+      final int port = await const HostPortScanner().findAvailablePort();
       expect(
-        VMService.connect(Uri.parse('http://host.invalid:9999/')),
+        VMService.connect(Uri.parse('http://localhost:$port')),
         throwsToolExit(),
       );
     });