go - 无法将 websocket 数据从 flutter 应用程序发送到服务器

Question

我正在尝试使用 flutter 应用程序客户端和 go server 创建服务器-客户端架构。
目前我正在尝试从 flutter 应用程序发送文本输入，以使用 Websockets 在服务器端读取和打印它。

我已经成功测试了我的 flutter 应用程序以从 https://www.websocket.org/echo 回显.
要连接到我的本地服务器，这里是相关位

用于连接服务器

  final channel = IOWebSocketChannel.connect('ws://localhost:8080/test');

当 onPressed 发送用户输入的数据时，调用 sendMessage()；

void sendMessage(){
    if(myController.text.isNotEmpty){
      channel.sink.add(myController.text);
    }
  }

我已阅读 https://godoc.org/github.com/gorilla/websocket docs 和其他博客了解 mux、handlefunc 和 listenandserve 功能，但我无法发送数据。

这是我的 Go 服务器:

package main

import (
    "fmt"
    "log"
    "net/http"
    "github.com/gorilla/websocket"
)

var upgrader = websocket.Upgrader{
        ReadBufferSize: 1024,
    }

func connectionHandler(w http.ResponseWriter, r *http.Request){
    conn, err := upgrader.Upgrade(w,r,nil)
    if err != nil {
        log.Println(err)
        return
    }

    for{
            messageType, p, err := conn.NextReader()
            fmt.Println(p)
            fmt.Println(messageType)
            if err != nil {
                log.Println(err)
                return
            }
    }

}

func main(){

    mux := http.NewServeMux()
    fmt.Printf("Connecting to server \n")

    mux.HandleFunc("/test", connectionHandler)

    log.Fatal(http.ListenAndServe(":8080", mux))

}

编辑:
添加了 Flutter 客户端代码。

import 'dart:async';

import 'package:flutter/material.dart';
import 'package:web_socket_channel/html.dart';
import 'package:web_socket_channel/io.dart';
import 'package:web_socket_channel/status.dart' as status;

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Shopping',
      initialRoute: 'home',
      theme: ThemeData(
        primarySwatch: Colors.lightBlue,
      ),
      routes: <String, WidgetBuilder>{
        'home': (BuildContext context) => HomePage(title: "Home"),
        '/shoppingpage': (BuildContext context) => ShoppingCart(title: "Shopping Cart Page"),
      },

    );
  }
}

class HomePage extends StatelessWidget {
  HomePage({Key key, this.title}) : super(key:key);
  final String title;
  final channel = IOWebSocketChannel.connect('ws://localhost:8080/test');
  TextEditingController myController = TextEditingController();
  final GlobalKey<ScaffoldState> _scaffoldkey = new GlobalKey<ScaffoldState>();

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      key: _scaffoldkey,
      body: Column(
        mainAxisAlignment: MainAxisAlignment.spaceEvenly,
        crossAxisAlignment: CrossAxisAlignment.center,
        children: <Widget>[
          FlatButton(
              onPressed: (){
                return (Navigator.of(context).pushNamed('/shoppingpage'));
              },
              child: Text('Start Game'),
              color: Colors.blue,
              splashColor: Colors.green,

          ),

          TextField(
            controller: myController,

          ),

          FloatingActionButton(
            onPressed: (){
              sendMessage();
              _scaffoldkey.currentState.showSnackBar(SnackBar(
                content: Text('Sent'),
              ));
            },
            child: Icon(Icons.send),
          ),

          StreamBuilder(
            stream: channel.stream,
            builder: (context, snapshot){
              return snapshot.hasData ? Text(snapshot.data.toString(),
              ) : CircularProgressIndicator();
            }
          ),
        ],
      ),
    );
  }

  void sendMessage(){
    if(myController.text.isNotEmpty){
      channel.sink.add(myController.text);
    }
  }

}



class ShoppingCart extends StatelessWidget {
  ShoppingCart({Key key, this.title}) : super(key: key);
  final String title;
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        leading: BackButton(onPressed: (){
          return Navigator.pop(context);
        }),
      ),
    );
  }
}

Answer 1

如果您在 PC 上运行 Go 服务器，但在移动/模拟器上运行 Flutter 应用程序，那么 localhost不起作用(它会指向手机/模拟器，而不是 PC)。

您需要使用从电话解析到 PC 的 IP 地址/主机名，并确保 Go 服务器绑定(bind)到网络可访问的 IP(并且没有防火墙)。