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