c# - SignalR:无法使用任何可用传输连接到服务器

Question

我在面向 .Net 4.6.2 的 WPF 应用程序中使用 Microsoft.AspNetCore.SignalR.Client (1.1.0v)。我正在像这样设置客户端:

public class SignalRClient
{
   private readonly HubConnection hubConnection;

   public SignalRClient()
   {
      this.hubConnection = new HubConnectionBuilder()
                .WithUrl("http://localhost:8089/MyDataHub")
                .Build();
   }

   // I'm calling the following method through a callback function in Autofac container after the DI container is built (but I tried doing this directly in the ctor and I got the same issue).

   public void Initialize()
   {
      Task.Factory.StartNew(
           () => 
           {
               // This is where I get the error.
               this.hubConnection.StartAsync().Wait();
           })
   }
}

服务器端日志显示:

16:56:45.380  Info | Request starting HTTP/1.1 GET http://localhost:8089/MyDataHub?id=7qLNfG-iV1Xr3oN_r8U_nA
info: Microsoft.AspNetCore.Hosting.Internal.WebHost[1]
      Request starting HTTP/1.1 POST http://localhost:8089/MyDataHub/negotiate  0
16:56:45.540  Info | Request starting HTTP/1.1 POST http://localhost:8089/MyDataHub/negotiate  0
info: Microsoft.AspNetCore.Hosting.Internal.WebHost[2]
      Request finished in 11.2669ms 200 application/json
16:56:45.552  Info | Request finished in 11.2669ms 200 application/json
info: Microsoft.AspNetCore.Hosting.Internal.WebHost[1]
      Request starting HTTP/1.1 POST http://localhost:8089/MyDataHub/negotiate  0
16:56:45.703  Info | Request starting HTTP/1.1 POST http://localhost:8089/MyDataHub/negotiate  0
info: Microsoft.AspNetCore.Hosting.Internal.WebHost[2]
      Request finished in 7.7109ms 200 application/json
16:56:45.703  Info | Request finished in 7.7109ms 200 application/json
info: Microsoft.AspNetCore.Hosting.Internal.WebHost[1]
      Request starting HTTP/1.1 GET http://localhost:8089/MyDataHub?id=4TN4k9wZWXsZ5iPyGNKSOA
16:56:45.719  Info | Request starting HTTP/1.1 GET http://localhost:8089/MyDataHub?id=4TN4k9wZWXsZ5iPyGNKSOA
info: Microsoft.AspNetCore.Hosting.Internal.WebHost[2]
      Request finished in 6.7847ms 200 application/octet-stream
16:56:45.719  Info | Request finished in 6.7847ms 200 application/octet-stream
fail: Microsoft.AspNetCore.SignalR.HubConnectionContext[5]
      Failed connection handshake.
16:56:51.013 Error | Failed connection handshake.
info: Microsoft.AspNetCore.Hosting.Internal.WebHost[2]
      Request finished in 20012.9772ms 101
16:57:05.393  Info | Request finished in 20012.9772ms 101

客户端错误信息:

Unable to connect to the server with any of the available transports

我不太明白这个错误是什么意思以及如何修复它。看起来服务器和客户端无法就传输达成一致？

请注意，服务器使用的是 Microsoft.AspNet.SignalR (2.4.0v)。服务器项目是一个 Asp.Net Core 2.1 应用程序(我不能在这里改变任何东西)。我正在尝试为客户端使用 AspNet Core 版本(这似乎是可能的，因为当我使用其他一些针对完全相同的框架版本的 .Net Framework WPF 和 Console 项目进行测试时，我没有收到此错误)。

1. 此特定错误的可能原因是什么？
2. 可能的修复。

编辑:

服务器中的路由映射:

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
   app.UseSignalR(routes => { routes.MapHub<MyDataHub>("/MyDataHub"); });
}

编辑 2:

MyDataHub.cs 类:

public class MyDataHub : Hub<IMyDataHub>
{
   public async Task SendMessage(MyData data)
   {
      await this.Clients.All.SendMessage(data);
   }

   // Some other business methods here defined in `IMyDataHub` interface that are meant to be invoked by clients.
}

Answer 1

事实证明，这个问题与颂歌本身没有太大关系。事实证明，解决方案中的不同项目(而且有很多!)正在使用不同版本的 System.Threading.Tasks.Extensions 包(一些使用 4.3.0 而另一个使用 4.5.1)。在 app.config 中有一个绑定(bind)重定向，比如

<dependentAssembly>
    <assemblyIdentity name="System.Threading.Tasks.Extensions" publicKeyToken="sdhke3jdj" culture="neutral" />
    <bindingRedirect oldVersion="0.0.0.0-4.1.0.0" newVersion="4.1.0.0" />
</dependentAssembly>

这没有多大意义，因为我在任何地方都没有 4.1.0。因此，我首先通过将其升级到 4.5.1 来整合整个解决方案的 System.Threading.Tasks.Extensions。然后从 app.config 文件中删除上述绑定(bind)重定向并开始工作。