使用Dart的http/dio包请求RSS链接遇解析错误：115≠13

尝试请求URL https://www.popularmechanics.com/rss/science/?src=rss，浏览器访问正常，但用Dart的http包或dio包发送请求时，均抛出解析异常：ClientException: Failed to parse HTTP, 115 does not match 13, uri=https://popularmechanics.com/rss/science/?src=rss

复现代码及报错 #

使用http包的代码 #

import 'package:http/http.dart' as http;

void main() {
  final client = http.Client();

  final Uri url = Uri.https('popularmechanics.com', '/rss/science/', {
    'src': 'rss'
  });

  try {
    client.get(url);
  } catch (e) {
    print(e);
  }
}

报错信息

Unhandled exception:
ClientException: Failed to parse HTTP, 115 does not match 13, uri=https://popularmechanics.com/rss/science/?src=rss
#0      IOClient.send (package:http/src/io_client.dart:121:7)
<asynchronous suspension>
#1      BaseClient._sendUnstreamed (package:http/src/base_client.dart:93:32)
<asynchronous suspension>

Process finished with exit code 255

使用dio包的代码 #

import 'package:dio/dio.dart';

void main() {
  final client = Dio();

  try {
    client.get('https://popularmechanics.com/rss/science/', queryParameters: {
      'src': 'rss'
    });
  } catch (e) {
    print(e);
  }
}

报错信息

Unhandled exception:
DioException [unknown]: null
Error: HttpException: Failed to parse HTTP, 115 does not match 13, uri = https://popularmechanics.com/rss/science/?src=rss
#0      DioMixin.fetch.<anonymous closure> (package:dio/src/dio_mixin.dart:507:7)
#1      _FutureListener.handleError (dart:async/future_impl.dart:180:22)
#2      Future._propagateToListeners.handleError (dart:async/future_impl.dart:858:47)
#3      Future._propagateToListeners (dart:async/future_impl.dart:879:13)
#4      Future._completeError (dart:async/future_impl.dart:655:5)
#5      _SyncCompleter._completeError (dart:async/future_impl.dart:63:12)
#6      _Completer.completeError (dart:async/future_impl.dart:27:5)
#7      Future.any.onError (dart:async/future.dart:618:45)
#8      _RootZone.runBinary (dart:async/zone.dart:1666:54)
#9      _FutureListener.handleError (dart:async/future_impl.dart:177:22)
#10     Future._propagateToListeners.handleError (dart:async/future_impl.dart:858:47)
#11     Future._propagateToListeners (dart:async/future_impl.dart:879:13)
#12     Future._completeError (dart:async/future_impl.dart:655:5)
#13     Future._asyncCompleteError.<anonymous closure> (dart:async/future_impl.dart:745:7)
#14     _microtaskLoop (dart:async/schedule_microtask.dart:40:21)
#15     _startMicrotaskLoop (dart:async/schedule_microtask.dart:49:5)
#16     _runPendingImmediateCallback (dart:isolate-patch/isolate_patch.dart:118:13)
#17     _Timer._runTimers (dart:isolate-patch/timer_impl.dart:405:11)
#18     _Timer._handleMessage (dart:isolate-patch/timer_impl.dart:429:5)
#19     _RawReceivePort._handleMessage (dart:isolate-patch/isolate_patch.dart:184:12)

Process finished with exit code 255

错误代码含义 #

• 13：是ASCII中的回车符（CR，\r）的十进制值。HTTP协议要求响应头结束后，必须以\r\n\r\n作为响应头与响应体的分隔符，解析器在这里期望找到回车符。
• 115：是ASCII中的字母s的十进制值。说明Dart的HTTP解析器在预期回车符的位置，收到了字符s，导致协议解析失败。

这种情况大多是因为服务器检测到请求来自非浏览器客户端（缺少必要请求头），返回了不符合标准HTTP协议的响应内容。

解决方案 #

核心修复：添加User-Agent请求头 #

模拟浏览器的请求头，让服务器返回标准HTTP响应：

修复后的http包代码

import 'package:http/http.dart' as http;

void main() async {
  final client = http.Client();

  final Uri url = Uri.https('popularmechanics.com', '/rss/science/', {
    'src': 'rss'
  });

  try {
    final response = await client.get(
      url,
      headers: {
        'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/114.0.0.0 Safari/537.36'
      },
    );
    print(response.body);
  } catch (e) {
    print(e);
  } finally {
    client.close();
  }
}

修复后的dio包代码

import 'package:dio/dio.dart';

void main() async {
  final client = Dio();

  try {
    final response = await client.get(
      'https://popularmechanics.com/rss/science/',
      queryParameters: {'src': 'rss'},
      options: Options(
        headers: {
          'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/114.0.0.0 Safari/537.36'
        },
      ),
    );
    print(response.data);
  } catch (e) {
    print(e);
  } finally {
    client.close();
  }
}

额外注意点 #

原代码未使用await处理异步请求，导致异常无法被当前代码块捕获（异步任务的异常会在全局抛出）。修复代码中已添加async/await，并确保客户端资源被正确关闭。

内容的提问来源于stack exchange，提问作者TijnvdEijnde