SignalR AspNetCore 无法连接到远程服务器 ---> System.Net.WebException

Question

我从 SignalR 客户端应用程序连接到 SignalRHub 时遇到问题，下面给出的是错误日志-

info: Microsoft.AspNetCore.Sockets.Client.WebSocketsTransport[0]
      02/01/2018 15:20:13: Connection Id f763a939-3fb9-4812-ae6e-dfe3198ab37b: Starting transport. Transfer mode: Text.
fail: Microsoft.AspNetCore.Sockets.Client.HttpConnection[9]02/01/2018 15:20:13: Connection Id f763a939-3fb9-4812-ae6e-dfe3198ab37b: Failed to start connection. Error starting transport 'WebSocketsTransport'.
System.Net.WebSockets.WebSocketException (0x80004005): Unable to connect to the remote server ---> System.Net.WebException: The remote server returned an error: (404) Not Found.
   at System.Net.HttpWebRequest.EndGetResponse(IAsyncResult asyncResult)
   at System.Threading.Tasks.TaskFactory`1.FromAsyncCoreLogic(IAsyncResult iar, Func`2 endFunction, Action`1 endAction, Task`1 promise, Boolean requiresSynchronization)
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Net.WebSockets.ClientWebSocket.<ConnectAsyncCore>d__21.MoveNext()
   at System.Net.WebSockets.ClientWebSocket.<ConnectAsyncCore>d__21.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Sockets.Client.WebSocketsTransport.<Connect>d__19.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Sockets.Client.WebSocketsTransport.<StartAsync>d__16.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Sockets.Client.HttpConnection.<StartTransport>d__46.MoveNext()

SignalR hub 与无状态服务结构服务一起运行，并部署在 azure 服务结构集群上。

在服务器端，我使用 nuget 库 Microsoft.AspNetCore.SignalR下面给出的是 AspNetCore 2.0 无状态服务端代码供参考-

Startup.cs：-

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;

namespace SampleChat
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc();
            services.AddSignalR();
            services.AddCors(options =>
            {
                options.AddPolicy("CorsPolicy",
                    builder => builder.AllowAnyOrigin()
                        .AllowAnyMethod()
                        .AllowAnyHeader()
                        .AllowCredentials());
            });
        }

        // 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.UseMvc();

            app.UseFileServer();

            app.UseCors("CorsPolicy");

            app.UseWebSockets();

            app.UseSignalR(routes => { routes.MapHub<ChatHub>("SignalRHub"); });
        }
    }
}

ChatHub.cs：-

using Microsoft.AspNetCore.SignalR;

namespace SampleChat
{
    public class ChatHub : Hub
    {
        public void Send(string message)
        {
            // Call the broadcastMessage method to update clients.
            Clients.All.InvokeAsync("Send", message);
        }
    }
}

示例聊天.cs

using System.Collections.Generic;
using System.Fabric;
using System.IO;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.ServiceFabric.Services.Communication.AspNetCore;
using Microsoft.ServiceFabric.Services.Communication.Runtime;
using Microsoft.ServiceFabric.Services.Runtime;

namespace SampleChat
{
    /// <summary>
    ///     The FabricRuntime creates an instance of this class for each service type instance.
    /// </summary>
    internal sealed class SampleChat : StatelessService
    {
        public SampleChat(StatelessServiceContext context)
            : base(context)
        {
        }

        /// <summary>
        ///     Optional override to create listeners (like tcp, http) for this service instance.
        /// </summary>
        /// <returns>The collection of listeners.</returns>
        protected override IEnumerable<ServiceInstanceListener> CreateServiceInstanceListeners()
        {
            return new[]
            {
                new ServiceInstanceListener(serviceContext =>
                    new KestrelCommunicationListener(serviceContext, "ServiceEndpoint", (url, listener) =>
                    {
                        ServiceEventSource.Current.ServiceMessage(serviceContext, $"Starting Kestrel on {url}");

                        return new WebHostBuilder()
                            .UseKestrel()
                            .ConfigureServices(
                                services => services
                                    .AddSingleton(serviceContext))
                            .UseContentRoot(Directory.GetCurrentDirectory())
                            .UseStartup<Startup>()
                            .UseServiceFabricIntegration(listener, ServiceFabricIntegrationOptions.None)
                            .UseUrls(url)
                            .Build();
                    }))
            };
        }
    }
}

在客户端，我使用 nuget 库Microsoft.AspNetCore.SignalR.Client 下面给出的是 SignalR 客户端代码-

程序.cs：-

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace SampleChatCoreApplication
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                SignalRConnector.ConnectoToSignalR().GetAwaiter().GetResult();
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex);
            };
            Console.ReadKey();
        }
    }
}

SignalRConnector.cs：-

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Microsoft.AspNetCore.SignalR.Client;

namespace SampleChatCoreApplication
{
    static class SignalRConnector
    {
        public static async Task<bool> ConnectoToSignalR()
        {
            var connection = new HubConnectionBuilder()
                .WithUrl("http://localhost:8634/SignalRHub")
                .WithConsoleLogger()
                .WithTransport(Microsoft.AspNetCore.Sockets.TransportType.WebSockets)
                .Build();
            connection.On<string>("Send", data =>
            {
                Console.WriteLine($"Received data: {data}");
            });

            await connection.StartAsync();

            await connection.InvokeAsync("Send", "Send data to Hub");

            Console.ReadKey();

            return true;
        }
    }
}

当我在本地系统中运行无状态服务时，我能够成功连接 SignalR Hub。

当服务在 azure 服务结构集群上运行时，我不确定为什么在将 SignalR 客户端与 SignalR 集线器连接时遇到问题。

对于附加信息，我检查了网络和负载均衡器规则，并且网络端不存在连接问题。（我已经通过在此服务中添加控制器来验证它，并且我能够从控制器检索结果）。

Answer 1

我做了一些研发，发现该问题可能与负载均衡器亲和力有关。为了验证负载均衡器关联性问题，我已经使用 HTTP 协议部署了应用程序，并且能够在多次重试连接尝试中与其连接。这给了我一个提示，负载均衡器亲和性可能会导致这里的问题。此外，我还检查了应用程序端口的负载均衡器规则，发现负载分配设置为无。根据我的理解，它应该是“SourceIPProtocol”。目前，该服务部署在 5 节点服务结构集群中，当我将服务缩减到 1 个节点时，我能够使用 .net 框架应用程序通过 HTTP 和 HTTPS 协议在第一次尝试中连接到该服务。

使用自签名证书部署服务。

这里剩下的唯一问题是我无法通过 HTTPS 协议从 .net 标准应用程序连接服务并收到错误 - The certificate authority is invalid or incorrect

为了从 .net 框架应用程序进行连接，我在信号器连接代码之前在给定行下方编写 - ServicePointManager.ServerCertificateValidationCallback += (o, c, ch, er) => true;

上面给出的代码在 .net 标准应用程序中不起作用。

通过进一步的研发，我发现在.NET Core中，ServicePointManager被HttpClientHandler实例本身的配置所取代。您需要调用.WithMessageHandlerIHubConnectionBuilder 实例并提供带有 set 的 HttpClientHandler 实例ServerCertificateCustomValidationCallback。

当我使用下面给定的代码时，我无法通过 HTTPS 协议连接 SignalR 集线器 -

var handler = new HttpClientHandler
                        {
                            ClientCertificateOptions = ClientCertificateOption.Manual,
                            ServerCertificateCustomValidationCallback = (httpRequestMessage, cert, cetChain, policyErrors) => { return true; }
                        };

                        Connection = new HubConnectionBuilder()
                            .WithUrl(url)
                            .WithTransport(Microsoft.AspNetCore.Sockets.TransportType.WebSockets)
                            .WithMessageHandler(handler)
                            .Build();

当我将传输更改为 TransportType.ServerSentEvents 或 TransportType.LongPolling 时，我能够毫无问题地连接 SignalR 集线器。