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// Copyright (c) 2015, 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.
library isolate.example.http_server;
import 'dart:async';
import 'dart:io';
import 'dart:isolate';
import 'package:isolate/isolate_runner.dart';
import 'package:isolate/ports.dart';
import 'package:isolate/runner.dart';
Future<Future<Object?> Function()> runHttpServer(
Runner runner, int port, HttpListener listener) async {
var stopPort = await, [port, listener]);
return () => _sendStop(stopPort);
Future<Object?> _sendStop(SendPort stopPort) =>
Future<SendPort> _startHttpServer(List<Object?> args) async {
var port = args[0] as int;
var listener = args[1] as HttpListener;
var server =
await HttpServer.bind(InternetAddress.anyIPv6, port, shared: true);
await listener.start(server);
return singleCallbackPort((SendPort resultPort) {
sendFutureResult(Future.sync(listener.stop), resultPort);
/// An [HttpRequest] handler setup. Gets called when with the server, and
/// is told when to stop listening.
/// These callbacks allow the listener to set up handlers for HTTP requests.
/// The object should be sendable to an equivalent isolate.
abstract class HttpListener {
Future start(HttpServer server);
Future stop();
/// An [HttpListener] that sets itself up as an echo server.
/// Returns the message content plus an ID describing the isolate that
/// handled the request.
class EchoHttpListener implements HttpListener {
static const _delay = Duration(seconds: 2);
static final _id = Isolate.current.hashCode;
final SendPort _counter;
StreamSubscription? _subscription;
Future start(HttpServer server) async {
print('Starting isolate $_id');
_subscription = server.listen((HttpRequest request) async {
await request.response.addStream(request);
print('Request to $hashCode');
var watch = Stopwatch()..start();
while (watch.elapsed < _delay) {
await Future.delayed(const Duration(milliseconds: 100));
print('Response from $_id');
await request.response.close();
Future stop() async {
print('Stopping isolate $_id');
await _subscription?.cancel();
void main(List<String> args) async {
var port = 0;
if (args.isNotEmpty) {
port = int.parse(args[0]);
var counter = ReceivePort();
HttpListener listener = EchoHttpListener(counter.sendPort);
// Used to ensure the requested port is available or to find an available
// port if `0` is provided.
var socket =
await ServerSocket.bind(InternetAddress.anyIPv6, port, shared: true);
port = socket.port;
var isolates = await Future.wait<IsolateRunner>(
Iterable.generate(5, (_) => IsolateRunner.spawn()), cleanUp: (isolate) {
var stoppers =
await Future.wait<Function>( isolate) {
return runHttpServer(isolate, socket.port, listener);
}), cleanUp: (shutdownServer) {
await socket.close();
var count = 25;
print('Server listening on port $port for $count requests');
print('Test with:');
print(' ab -l -c10 -n $count http://localhost:$port/');
print("where 'ab' is ApacheBench from, e.g., apache2_tools.");
await for (var _ in counter) {
if (count == 0) {
print('Shutting down');
for (var stopper in stoppers) {
await stopper();