Websocket：使用 Dart 客户端和 Autobahn-python 服务器

Question

我是 websocket 的新手，正在尝试使用用 Dart/flutter 编写的客户端连接到使用 Autobahn 用 Python 编写的服务器。

问题

由于Autobahn 的服务器示例文档没有给出有关使用ws://地址的案例，因此我尝试根据其服务器工厂文档自己创建这样的服务器，但失败了。

代码

服务器代码看起来像这样

# from autobahn.twisted.websocket import WebSocketServerProtocol
from autobahn.asyncio.websocket import WebSocketServerProtocol

class MyServerProtocol(WebSocketServerProtocol):

    def onConnect(self, request):
        print("Client connecting: {}".format(request.peer))

    def onOpen(self):
        print("WebSocket connection open.")

    def onMessage(self, payload, isBinary):
        if isBinary:
            print("Binary message received: {} bytes".format(len(payload)))
        else:
            print("Text message received: {}".format(payload.decode('utf8')))

        # echo back message verbatim
        self.sendMessage(payload, isBinary)

    def onClose(self, wasClean, code, reason):
        print("WebSocket connection closed: {}".format(reason))


if __name__ == '__main__':
    import asyncio

    from autobahn.asyncio.websocket import WebSocketServerFactory
    factory = WebSocketServerFactory(url='ws://myhost.com/somepat:9001')
    factory.protocol = MyServerProtocol

    loop = asyncio.get_event_loop()
    coro = loop.create_server(factory, '127.0.0.1', 9001)
    server = loop.run_until_complete(coro)

    try:
        print('starting server ...')
        loop.run_forever()
    except KeyboardInterrupt:
        pass
    finally:
        server.close()
        loop.close()

客户端代码改编自flutter文档，只有通道是我自己的：

import 'package:flutter/foundation.dart';
import 'package:web_socket_channel/io.dart';
import 'package:flutter/material.dart';
import 'package:web_socket_channel/web_socket_channel.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final title = 'WebSocket Demo';
    return MaterialApp(
      title: title,
      home: MyHomePage(
        title: title,
        // channel: IOWebSocketChannel.connect('ws://echo.websocket.org'),
        channel: IOWebSocketChannel.connect('ws://myhost.com/somepat:9001'),
      ),
    );
  }
}

class MyHomePage extends StatefulWidget {
  final String title;
  final WebSocketChannel channel;

  MyHomePage({Key key, @required this.title, @required this.channel})
      : super(key: key);

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  TextEditingController _controller = TextEditingController();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Padding(
        padding: const EdgeInsets.all(20.0),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: <Widget>[
            Form(
              child: TextFormField(
                controller: _controller,
                decoration: InputDecoration(labelText: 'Send a message'),
              ),
            ),
            StreamBuilder(
              stream: widget.channel.stream,
              builder: (context, snapshot) {
                return Padding(
                  padding: const EdgeInsets.symmetric(vertical: 24.0),
                  child: Text(snapshot.hasData ? '${snapshot.data}' : ''),
                );
              },
            )
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _sendMessage,
        tooltip: 'Send message',
        child: Icon(Icons.send),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }

  void _sendMessage() {
    if (_controller.text.isNotEmpty) {
      widget.channel.sink.add(_controller.text);
    }
  }

  @override
  void dispose() {
    widget.channel.sink.close();
    super.dispose();
  }
}

预期的

运行上面的服务器和客户端代码，我希望看到来自客户端的任何输入字符串都从服务器返回并显示在客户端智能手机文本条目下方的 UI 上。

观察

什么都没有回来。 来自客户端的日志

Launching lib/main.dart on LIO AN00m in debug mode...
Running Gradle task 'assembleDebug'...
✓ Built build/app/outputs/flutter-apk/app-debug.apk.
Installing build/app/outputs/flutter-apk/app.apk...
Debug service listening on ws://127.0.0.1:54635/rsYDNkqGhYI=/ws
Syncing files to device LIO AN00m...
I/DecorView[](28048):  old windowMode:1 new windoMode:1
I/AwareBitmapCacher(28048): init lrucache size: 2097152 pid=28048
D/stylus  (28048): init stylus touchlistener.
I/Hwaps   (28048): APS: EventAnalyzed: initAPS: version is 11.0.0.4
D/Hwaps   (28048): Fpsrequest create,type:EXACTLY_IDENTIFY
D/Hwaps   (28048): Fpsrequest create,type:EXACTLY_IDENTIFY
D/Hwaps   (28048): Fpsrequest create,type:OPENGL_SETTING
D/Hwaps   (28048): FpsController create
D/Hwaps   (28048): APS: EventAnalyzed: reInitFpsPara :mBaseFps = 60; mMaxFps = 60
W/Settings(28048): Setting device_provisioned has moved from android.provider.Settings.Secure to android.provider.Settings.Global.
V/HiTouch_HiTouchSensor(28048): User setup is finished.
W/HwApsManager(28048): HwApsManagerService, registerCallback, start !
D/Hwaps   (28048): APS: EventAnalyzed: registerCallbackInApsManagerService, mPkgName:com.example.flutter_websocket; result = true
W/InputMethodManager(28048): startInputReason = 4
I/InputMethodManager(28048): showSoftInput
W/InputMethodManager(28048): startInputReason = 3
V/AudioManager(28048): querySoundEffectsEnabled...

尝试

我尝试了几个不同的地址字符串，例如

'ws://127.0.0.1:9001'

'ws://localhost:9001'

但它们都不起作用。

问题

看来我缺乏一些入门的基础知识。 我来自 ZeroMQ 世界，其中所有地址几乎都是隐藏实现细节的标签，这对像我这样的网络编程新手很友好，但似乎也让我无法理解 WebSocket 协议。

我错在哪里以及如何调试这种情况？ 任何指针表示赞赏。

Answer 1

您需要在 python 代码中输入您的 pc/服务器的 IP 地址，您可以通过运行ipconfig检查出来，您也应该在 dart 应用程序上输入相同的 IP。 localhost 是一个主机名，指的是当前用于访问它的设备，其他设备无法访问其他本地主机，但可以访问其 IP 地址。