[io/http] Fix race condition where RawSecureSocket dispatches read events after shutdown

[Colton127]

This PR resolves an issue where RawSecureSocket potentially emits a RawSocketEvent.read event after the read-side of the socket has been closed. The receiver would then attempt to read from the socket, which throws SocketException: Reading from a closed socket.

Issue: #62514

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[mraleph]

@Colton127 could you include this as a regression test (you can place it in tests/standalone/io/regress_62514_test.dart):

// Copyright (c) 2026, 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.
//
// OtherResources=certificates/server_chain.pem
// OtherResources=certificates/server_key.pem

// Test that cancellation of subscription to [SecureSocket] works as
// expected.

import 'dart:async';
import 'dart:io';
import 'dart:typed_data';

import 'package:async_helper/async_helper.dart';
import 'package:expect/expect.dart';

String relativeToScript(path) => Platform.script.resolve(path).toFilePath();

final String serverCert = relativeToScript('certificates/server_chain.pem');
final String serverKey = relativeToScript('certificates/server_key.pem');

void main() {
  asyncTest(() async {
    final serverContext = SecurityContext()
      ..useCertificateChain(serverCert)
      ..usePrivateKey(serverKey, password: 'dartdart');

    final secureServer = await SecureServerSocket.bind(
      InternetAddress.loopbackIPv4,
      0,
      serverContext,
    );

    final dataStream = Stream.fromIterable(
      Iterable<List<int>>.generate(100, (_) => Uint8List(1024 * 1024)),
    );

    secureServer.listen((client) async {
      await dataStream.pipe(client);
      await client.close();
    });

    final secureClient = await SecureSocket.connect(
      InternetAddress.loopbackIPv4,
      secureServer.port,
      context: SecurityContext()..setTrustedCertificates(serverCert),
    );
    late final StreamSubscription clientSub;
    clientSub = secureClient.listen((event) async {
      clientSub.cancel();
    });
    await clientSub.asFuture();

    await Future.wait([secureClient.close(), secureServer.close()]);
  });
}

[Colton127]

@mraleph Got it, thank you

[copybara-service]

https://dart-review.googlesource.com/c/sdk/+/475941 has been updated with the latest commits from this pull request.

[copybara-service]

https://dart-review.googlesource.com/c/sdk/+/475941 has been updated with the latest commits from this pull request.