Asp.Net Core SignalR 无法从 Android Studio 模拟器客户端连接

Question

I have a SignalR Server running on

http://localhost:50926/testhub

I can connect to the hub on the same machine with a .net signalR client and it works as expected. I can not connect to it on an Android Client running in Android Studio. I understand that you can not connect to localhost from an emulator so I have set up an ng rock proxy and the proxy appears to be connecting to localhost from postman but I can not connect from Emulator. I understand that the android client can only use websockets so I have configured the hub to use web sockets like this:

 public void ConfigureServices(IServiceCollection services)
    {
        services.AddSignalR();
    }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IHostingEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }
        app.UseWebSockets();
        app.UseSignalR((configure) =>
        {
            var desiredTransports =
                HttpTransportType.WebSockets;

            configure.MapHub<TestHub>("/testhub", (options) =>
            {
                options.Transports = desiredTransports;
            });
        });
        app.Run(async (context) =>
           {
               await context.Response.WriteAsync("Hello World!");
           });
    }

Here is my Android Client Code:

public class MainActivity extends AppCompatActivity {

HubConnection hubConnection;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    hubConnection = HubConnectionBuilder.create("http://c03e07e9.ngrok.io/testhub").build();
    hubConnection.start();
    if (hubConnection.getConnectionState()== HubConnectionState.CONNECTED){
        hubConnection.send("ReceiveMessage","hello from android");
    }


}

} And the gradle:

 android {
compileSdkVersion 28
defaultConfig {
    applicationId "com.ct.sigrtest2"
    minSdkVersion 28
    targetSdkVersion 28
    versionCode 1
    versionName "1.0"
    testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}
buildTypes {
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
    }
}
compileOptions {
    sourceCompatibility = '1.8'
    targetCompatibility = '1.8'
}

}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
    implementation 'com.microsoft.signalr:signalr:1.0.0'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso- 
    core:3.0.2'

} The android client does not throw any errors and will not connect to ngrok Can anyone advise why I can not connect to the hub?

Answer 1

Ngrok 似乎不支持 websockets :(

Answer 2

1) Check your permissions in AndroidManifext.xml

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

2) Try to use local ip address 10.0.2.2 instead localhost (if you want localhost)

hubConnection = HubConnectionBuilder.create("http://10.0.2.2:port/testhub").build();

3) Use HubConnectionTask class for starting:

class HubConnectionTask extends AsyncTask<HubConnection, Void, Void> {

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
    }

    @Override
    protected Void doInBackground(HubConnection... hubConnections) {
        HubConnection hubConnection = hubConnections[0];
        hubConnection.start().blockingAwait();
        return null;
    }
}

new HubConnectionTask().execute(hubConnection);