为什么在收到完整标头之前经常发生颤动返回连接关闭答案

【问题标题】：why flutter often occur return connection closed before full header was received为什么在收到完整标头之前经常发生颤动返回连接关闭
【发布时间】：2022-08-15 04:49:10
【问题描述】：

我使用HTTP 连接到API，我尝试了一些类似2.5, 2.10.5, 3 的flutter sdk，但仍然经常出现同样的问题，返回connection closed before full header was received。它可能发生在随机 api 和我构建的所有应用程序中。

它是我的代码示例

Future<dynamic> getGoodSolution() async {
    final url = Uri.parse(\'$url\');
    final headers = {HttpHeaders.contentTypeHeader: \'application/json\', HttpHeaders.authorizationHeader: \'Bearer mytoken123\'};
    var map = <String, dynamic>{};
    map[\"xxx\"] = \"123\";
    // print(headers);

    try {
      final response = await client.post(url, headers: headers, body: json.encode(map));
      final data = xxxFromJson(response.body);
      return data;
    } catch (e) {
      print(e);
      return null;
    }
  }

标签： flutter

【解决方案1】：

有一个issue ongoing on the Flutter repo 描述了您的问题。

给定的解决方法之一是使用HttpClient 并将allowLegacyUnsafeRenegotiation 属性设置为true

void main() async {
  final context = SecurityContext.defaultContext;
  context.allowLegacyUnsafeRenegotiation = true;
  final httpClient = HttpClient(context: context);
  final client = IOClient(httpClient);

  await client.get(Uri.parse('https://your_uri.net'));
}

此解决方案仅适用于移动设备，http 包不应在 Web 模式下使用。

【讨论】：

allowLegacyUnsafeRenegotiation 无法使用。 The setter 'allowLegacyUnsafeRenegotiation' isn't defined for the type 'SecurityContext'
您至少需要 Flutter 3.0.0，因为它已在 Dart 2.17 中更新github.com/dart-lang/sdk/blob/main/CHANGELOG.md#dartio-2

【解决方案2】：

我通过使用 HTTP (More info) 包的 send() 方法解决了这个问题

Future<dynamic> getGoodSolution() async {
  final url = Uri.parse('$url');
  final headers = {HttpHeaders.contentTypeHeader: 'application/json',HttpHeaders.authorizationHeader: 'Bearer mytoken123'};
  var map = <String, dynamic>{};
  map["xxx"] = "123";

  try {
    var request = http.Request('POST', url);

    request.headers.addAll(headers);
    request.body = json.encode(map);

    var streamedResponse = await request.send();
    var response = await http.Response.fromStream(streamedResponse);

    final data = xxxFromJson(response.body);
    return data;
  } catch (e) {
    print(e);
    return null;
  }
}

【讨论】：