I have a small console application built with .NET 8. This application reads the body of a web response, and it works as expected on Windows. However, it doesn’t work on Ubuntu 22 or Ubuntu 24 fresh installation.

Here is the program:

using System.Net;

var httpClient = new HttpClient();
var data = httpClient.GetStringAsync("https://www.nu.nl").Result;
Console.WriteLine(data);

When I run it on Ubuntu, I receive the following error or a timeout:

root@:/tmp/test# dotnet consoletest.dll

Unhandled exception. System.AggregateException: One or more errors occurred. (An error occurred while sending the request.)
 ---> System.Net.Http.HttpRequestException: An error occurred while sending the request.
 ---> System.IO.IOException: Unable to read data from the transport connection: Connection reset by peer.
 ---> System.Net.Sockets.SocketException (104): Connection reset by peer
   at System.Net.Sockets.Socket.AwaitableSocketAsyncEventArgs.CreateException(SocketError error, Boolean forAsyncThrow)
   at System.Net.Sockets.Socket.AwaitableSocketAsyncEventArgs.ReceiveAsync(Socket socket, CancellationToken cancellationToken)
   at System.Net.Sockets.Socket.ReceiveAsync(Memory`1 buffer, SocketFlags socketFlags, Boolean fromNetworkStream, CancellationToken cancellationToken)
   at System.Net.Sockets.NetworkStream.ReadAsync(Memory`1 buffer, CancellationToken cancellationToken)
   at System.Net.Security.SslStream.EnsureFullTlsFrameAsync[TIOAdapter](CancellationToken cancellationToken, Int32 estimatedSize)
   at System.Runtime.CompilerServices.PoolingAsyncValueTaskMethodBuilder`1.StateMachineBox`1.ExecutionContextCallback(Object s)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Runtime.CompilerServices.PoolingAsyncValueTaskMethodBuilder`1.StateMachineBox`1.MoveNext()
   at System.Threading.Tasks.Sources.ManualResetValueTaskSourceCore`1.SetResult(TResult result)
   at System.Net.Sockets.SocketAsyncEventArgs.TransferCompletionCallbackCore(Int32 bytesTransferred, Memory`1 socketAddress, SocketFlags receivedFlags, SocketError socketError)
   at System.Net.Sockets.SocketAsyncEngine.System.Threading.IThreadPoolWorkItem.Execute()
   at System.Threading.ThreadPoolWorkQueue.Dispatch()
   at System.Threading.PortableThreadPool.WorkerThread.WorkerThreadStart()
--- End of stack trace from previous location ---

   --- End of inner exception stack trace ---
   at System.Net.Security.SslStream.EnsureFullTlsFrameAsync[TIOAdapter](CancellationToken cancellationToken, Int32 estimatedSize)
   at System.Runtime.CompilerServices.PoolingAsyncValueTaskMethodBuilder`1.StateMachineBox`1.System.Threading.Tasks.Sources.IValueTaskSource<TResult>.GetResult(Int16 token)
   at System.Net.Security.SslStream.ReadAsyncInternal[TIOAdapter](Memory`1 buffer, CancellationToken cancellationToken)
   at System.Runtime.CompilerServices.PoolingAsyncValueTaskMethodBuilder`1.StateMachineBox`1.System.Threading.Tasks.Sources.IValueTaskSource<TResult>.GetResult(Int16 token)
   at System.Net.Http.HttpConnection.InitialFillAsync(Boolean async)
   at System.Net.Http.HttpConnection.SendAsync(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken)
   --- End of inner exception stack trace ---
   at System.Net.Http.HttpConnection.SendAsync(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken)
   at System.Net.Http.HttpConnectionPool.SendWithVersionDetectionAndRetryAsync(HttpRequestMessage request, Boolean async, Boolean doRequestAuth, CancellationToken cancellationToken)
   at System.Net.Http.RedirectHandler.SendAsync(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken)
   at System.Net.Http.HttpClient.GetStringAsyncCore(HttpRequestMessage request, CancellationToken cancellationToken)
   --- End of inner exception stack trace ---
   at System.Threading.Tasks.Task`1.GetResultCore(Boolean waitCompletionNotification)
   at Program.<Main>$(String[] args) in C:tempconsoletestProgram.cs:line 9

The Ubuntu installation is fresh, with the .NET 8 SDK and runtime installed. All packages are up to date.

Interestingly, the program works with some other websites. I also tried specifying TLS 1.3 in the code, but the issue persists.

It seems that the tool might be waiting for content or encountering an SSL issue, but I’m unable to pinpoint the exact cause.

What steps can I take to determine why it’s not working?