我有C#.NET Framework SignalR客户端应用程序&ASP.NET Core 2.1服务器。当我试图通过WebSockets启动到SignalR Hub的连接时，我遇到了异常。
System.AggregateException: Unable to connect to the server with any of the available transports.
--->
Microsoft.AspNetCore.Http.Connections.Client.TransportFailedException: WebSockets failed: The 'User-Agent' header must be modified using the appropriate property or method. Имя параметра: name
--->
System.ArgumentException: The 'User-Agent' header must be modified using the appropriate property or method. Parameter name: name
in System.Net.WebHeaderCollection.ThrowOnRestrictedHeader(String headerName)
in System.Net.WebHeaderCollection.Set(String name, String value)
in Microsoft.AspNetCore.Http.Connections.Client.Internal.WebSocketsTransport..ctor(HttpConnectionOptions httpConnectionOptions, ILoggerFactory loggerFactory, Func`1 accessTokenProvider)
in Microsoft.AspNetCore.Http.Connections.Client.Internal.DefaultTransportFactory.CreateTransport(HttpTransportType availableServerTransports)
in Microsoft.AspNetCore.Http.Connections.Client.HttpConnection.<StartTransport>d__47.MoveNext()
in System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
in System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
in System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task task)
in Microsoft.AspNetCore.Http.Connections.Client.HttpConnection.<SelectAndStartTransport>d__44.MoveNext()
in Microsoft.AspNetCore.Http.Connections.Client.HttpConnection.<SelectAndStartTransport>d__44.MoveNext()
in System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
in System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
in Microsoft.AspNetCore.Http.Connections.Client.HttpConnection.<StartAsyncCore>d__41.MoveNext()
in System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
in System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
in Microsoft.AspNetCore.Http.Connections.Client.HttpConnection.<StartAsync>d__40.MoveNext()
in System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
in System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
in Microsoft.AspNetCore.Http.Connections.Client.HttpConnectionFactory.<ConnectAsync>d__3.MoveNext()
in Microsoft.AspNetCore.Http.Connections.Client.HttpConnectionFactory.<ConnectAsync>d__3.MoveNext()
in System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
in System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
in Microsoft.AspNetCore.SignalR.Client.HubConnection.<StartAsyncCore>d__58.MoveNext()
in System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
in System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
in Microsoft.AspNetCore.SignalR.Client.HubConnection.<StartAsyncInner>d__50.MoveNext()
in System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
in System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
in Microsoft.AspNetCore.SignalR.Client.HubConnection.<StartAsync>d__49.MoveNext()
in System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
in System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
in System.Runtime.CompilerServices.TaskAwaiter.GetResult()
in WPF.MainWindow.<<-ctor>b__4_4>d.MoveNext() in repository/MainWindow.xaml.cs:line 90
(#0) Microsoft.AspNetCore.Http.Connections.Client.TransportFailedException: WebSockets failed: The 'User-Agent' header must be modified using the appropriate property or method Parameter name: name
---> System.ArgumentException: The 'User-Agent' header must be modified using the appropriate property or method Parameter name: name
in System.Net.WebHeaderCollection.ThrowOnRestrictedHeader(String headerName)
in System.Net.WebHeaderCollection.Set(String name, String value)
in Microsoft.AspNetCore.Http.Connections.Client.Internal.WebSocketsTransport..ctor(HttpConnectionOptions httpConnectionOptions, ILoggerFactory loggerFactory, Func`1 accessTokenProvider)
in Microsoft.AspNetCore.Http.Connections.Client.Internal.DefaultTransportFactory.CreateTransport(HttpTransportType availableServerTransports)
in Microsoft.AspNetCore.Http.Connections.Client.HttpConnection.<StartTransport>d__47.MoveNext()
in System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
in System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
in System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task task)
in Microsoft.AspNetCore.Http.Connections.Client.HttpConnection.<SelectAndStartTransport>d__44.MoveNext()
(#1) Microsoft.AspNetCore.Http.Connections.Client.TransportFailedException: ServerSentEvents failed: The transport is disabled by the client.<---
(#2) Microsoft.AspNetCore.Http.Connections.Client.TransportFailedException: LongPolling failed: The transport is disabled by the client.
<---
代码：
HubConnection Connection = new HubConnectionBuilder().WithUrl($"..", options => {
options.UseDefaultCredentials = true;
options.Transports = Microsoft.AspNetCore.Http.Connections.HttpTransportType.WebSockets;
options.Headers["user-agent"] = "Mozilla/5.0";
}).Build();
Task.Run(async () =>
{
try
{
await Connection.StartAsync(); // exception thrown here
}
catch (Exception ex)
{
// handle ex
}
});
我看到了这个github问题，这个问题和这个问题，但我不理解附件中的解决方案。
为了避免此异常，我需要添加什么用户代理标头？
我认为这应该有效：
using System.Reflection;
using System.Net.WebSockets;
using Microsoft.AspNetCore.Http.Connections;
//
static void HackWebSocketConfiguration( ClientWebSocketOptions wso )
{
FieldInfo whcField = typeof(ClientWebSocketOptions).GetField( "requestHeaders", BindingFlags.Instance | BindingFlags.NonPublic );
WebHeaderCollection whc = (WebHeaderCollection)whcField.GetValue( wso );
MethodInfo awov = typeof(ClientWebSocketOptions).GetMethod( "AddWithoutValidate", BindingFlags.Instance | BindingFlags.NonPublic );
awov.Invoke( whc, /*headerName:*/ "User-Agent", /*headerValue:*/ "Toaster/1.0" );
}
//
HubConnection Connection = new HubConnectionBuilder()
.WithUrl( $"..", options =>
{
options.UseDefaultCredentials = true;
options.Transports = HttpTransportType.WebSockets;
options.WebSocketConfiguration = ( ClientWebSocketOptions wso ) =>
{
HackWebSocketConfiguration( wso );
};
})
.Build();
由于这是一个.NET Framework错误，切换到.NET Core帮助我解决了这个问题。