Andoird 无法连接到 Blazor 服务器上运行的 SignalR

Question

我正在尝试连接到使用 android 托管的 .net 6 Core Blazor WASM 核心。

String hubUrl = "http://192.168.254.173:5050/notification?parameter=1010072";
if (isReachable) {
    hubConnection = HubConnectionBuilder.create(hubUrl).build();
    if (hubConnection.getConnectionState() != HubConnectionState.CONNECTED) {
        hubConnection.start();
        hubConnection.on("MessageModelToClients", (messageModel) -> {
            Log.i("TAG", messageModel.getMessage());
        }, MessageModel.class);
        if (hubConnection.getConnectionState() == HubConnectionState.CONNECTED) {
            Log.i("TAG", "Connected");
        } else {
            Log.e("TAG", "Failed to establish connection to SignalR hub.");
        }
    }
} else {
    System.out.println("IP address is not reachable.");
}

这是我的毕业典礼，

implementation ("com.microsoft.signalr:signalr:7.0.0")

这是我在核心托管 Blazor WASM 上的中心

public class NotificationHub : Hub 
{
    ....
    
    public override async Task OnConnectedAsync()
    {
        Console.WriteLine("Connecting...");
        var userId= Context.GetHttpContext()!.Request.Query["userid"];
        var connectionId = Context.ConnectionId;
        AddUser(connectionId, userId);
        var messageModel = new MessageModel
        {
            IsPrivate = false,
            Message = $"Logged in User: {userId}",
            Recipient = string.Empty,
            Sender = SERVER_NAME
        };
        await SendConnectedUsers();
        await SendObjectToAll(messageModel);

        Console.WriteLine($"CONNECTED: {connectionId}");

        await base.OnConnectedAsync();
    }
    
    
    ...
}

在Program.cs中

builder.Services.AddSignalR();
app.UseEndpoints(endpoints =>
{
    endpoints.MapHub<NotificationHub>("/notification");
});

你能指出我做错了什么吗？

Answer 1

检查您的代码和设置后，有一些建议供您排除故障。

1. 确保您的 Android 设备未使用蜂窝数据网络，因为您使用的是

   192.168.254.173

   私有 IP。同网段下可以正常工作

2. 确保参数相同，SignalR 客户端的 URL 应为 http://192.168.254.173:5050/notification?userid=1010072。

3. 尝试在OnConnectedAsync中设置断点，看看能否进入这个方法。

   ① 如果是，就可以调试了。会发现问题的。
   ② 如果没有，请按照第4点打包

   Cors

   。

4. 我们可以启用所有Origin进行测试。中间件顺序非常重要。

   public class Program
   {
       public static void Main(string[] args)
       {
           ...
           // allow all Origin
           builder.Services.AddCors(options => options.AddPolicy("CorsPolicy", builder =>
           {
               builder.AllowAnyMethod()
                   .SetIsOriginAllowed(_ => true)
                   .AllowAnyHeader()
                   .AllowCredentials();
           }));
           ...
           var app = builder.Build();
   
           // Configure the HTTP request pipeline.
           if (!app.Environment.IsDevelopment())
           {
               app.UseExceptionHandler("/Home/Error");
               // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
               app.UseHsts();
           }
   
           app.UseHttpsRedirection();
           app.UseStaticFiles();
   
           app.UseRouting();
   
           // add this line
           app.UseCors("CorsPolicy");
   
           app.UseAuthorization();
   
           app.MapControllerRoute(
               name: "default",
               pattern: "{controller=Home}/{action=Index}/{id?}");
   
           app.Run();
       }
   }