Connection closed before full header was received, uri = http://127.0.0.1:54627/-白红宇

很多人运行flutter项目时，出现如下错误

Error connecting to the service protocol: HttpException: Connection closed before full header was received, uri = http://127.0.0.1:54627/p1NdakJReqU=/ws复制代码

这个问题目前发现在安卓模拟器上出现频率较多，之前为了简单方便，都建议使用真机测试。今天有时间寻找研究一下这个问题，多谢网友【itskamui】(网名)的协作一起研究。

情况1：

可以看到日志里面有No connected devices，判断应该是模拟器没有链接成功，可以尝试各种 adb devices -l 或者 flutter devices 查看是不是能看到模拟器，如果看不到，重启模拟器，再试。

情况2：

通过正常的flutter run运行得到简单日志

Launching lib/main.dart on Android SDK built for x86 in debug mode...Initializing gradle...Resolving dependencies...Running Gradle task 'assembleDebug'...Built build/app/outputs/apk/debug/app-debug.apk.Installing build/app/outputs/apk/app.apk...Error connecting to the service protocol: HttpException: Connection closed before full header was received, uri = http://127.0.0.1:54627/p1NdakJReqU=/ws复制代码

使用flutter run -v可以输出更完整的日志

....[   +1 ms] Stopping app 'app.apk' on Android SDK built for x86.[        ] executing: /Users/wei/Library/Android/sdk/platform-tools/adb -s emulator-5554 shell am force-stop pt.tribeiro.flutter_pdf_viewer_example[  +89 ms] executing: /Users/wei/Library/Android/sdk/platform-tools/adb -s emulator-5554 shell pm list packages pt.tribeiro.flutter_pdf_viewer_example[  +31 ms] package:pt.tribeiro.flutter_pdf_viewer_example[   +3 ms] executing: /Users/wei/Library/Android/sdk/platform-tools/adb -s emulator-5554 shell cat/data/local/tmp/sky.pt.tribeiro.flutter_pdf_viewer_example.sha1[  +26 ms] 01742bfabba2b904071ee66da7111e5f6bd5e7f2[        ] Latest build already installed.[        ] Android SDK built for x86 startApp[   +1 ms] executing: /Users/wei/Library/Android/sdk/platform-tools/adb -s emulator-5554 shell am start -a android.intent.action.RUN -f 0x20000000--ez enable-background-compilation true --ez enable-dart-profiling true --ez enable-checked-mode true --ez verify-entry-points truept.tribeiro.flutter_pdf_viewer_example/pt.tribeiro.flutter_plugin_pdf_viewer_example.MainActivity[  +65 ms] Starting: Intent { act=android.intent.action.RUN flg=0x20000000cmp=pt.tribeiro.flutter_pdf_viewer_example/pt.tribeiro.flutter_plugin_pdf_viewer_example.MainActivity (has extras) }[   +1 ms] Waiting for observatory port to be available...[ +939 ms] Observatory URL on device: http://127.0.0.1:41575/z9Mve5wOFL8=/[   +1 ms] executing: /Users/wei/Library/Android/sdk/platform-tools/adb -s emulator-5554 forward tcp:0 tcp:41575[   +8 ms] 53415[        ] Forwarded host port 53415 to device port 41575 for Observatory[   +7 ms] Connecting to service protocol: http://127.0.0.1:53415/z9Mve5wOFL8=/[  +22 ms] Error connecting to the service protocol: HttpException: Connection closed before full header was received, uri =           http://127.0.0.1:53415/z9Mve5wOFL8=/ws[   +3 ms] "flutter run" took 9,137ms.[        ] "flutter run" took 9,137ms.....复制代码

Dart Observatory (语句级的单步调试和分析器) 是调试工具也要靠这个工具启动的服务来实现flutter热加载，有兴趣的可以查看文档研究一下

所以一开始以为是端口问题，使用参数--observatory-port=指定了端口，发现是无效的。

flutter sdk 的issues上有好多类似问题。

有说需要用PowerShell运行的，经过尝试无效。

有说需要管理员身份运行的，尝试无效。

后来发现模拟器的系统镜像版本是Android 10或者是Android Q或者是Android 9.+(api 29)

然后尝试下载使用低版本的系统，重新创建一个模拟器，问题就解决了。

猜测应该是Android Q目前还是beta版本，所以都会出现这个问题，目前在Android Q下还是没有办法能解决这个问题。

还有不排除设置了代理的可能性。

所以目前解决这个问题的办法是：

1、使用低版本的系统镜像

2、使用真机吧、真机吧、真机吧

作者博客：