Error using ClientWebSocket: The 'Connection' header value 'Upgrade,Keep-Alive' is invalid. .NET Framework 4.7.2

Question

Error using ClientWebSocket: The 'Connection' header value 'Upgrade,Keep-Alive' is invalid. .NET Framework 4.7.2

Marcelo Cantú 0

Hi, Im using .NET Framework 4.7.2 trying to connect to a WebSocket as a client, however I keep getting the same error over and over:

System.Net.WebSockets.WebSocketException (0x80004005): The 'Connection' header value 'Upgrade,Keep-Alive' is invalid.

at System.Net.WebSockets.ClientWebSocket.ValidateResponse(HttpWebRequest request, HttpWebResponse response)

at System.Net.WebSockets.ClientWebSocket.<ConnectAsyncCore>d__21.MoveNext()"

This is my code:

  using (ClientWebSocket webSocket = new ClientWebSocket())

  {


  try

  {

      webSocket.ConnectAsync(serverUri, CancellationToken.None).Wait();

      Console.WriteLine("Connected!");

      webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, "Closing", CancellationToken.None).Wait();

      Console.WriteLine("Closed!");

  }

  catch (Exception e)

  {

      Console.WriteLine($"Exception: {e.Message}");

  }
  }

It seems that the class is putting Keep.Alive in the connection header and that is invalid. I tried modifying the header but it doesnt let me. Im able to connect with Postman and other libraries so the problem is not the server.

Viorel 122.5K Reputation points

2024-06-18T04:55:47.2066667+00:00
Maybe the server returns a response, which is unsupported in .NET Framework:

https://github.com/websocket-client/websocket-client/issues/626

Check if it works using .NET 7 or 8.

Anonymous

Use .NET Core or .NET 5+

If possible, migrate to .NET Core or .NET 5+, as these versions have better support for WebSocket and fewer issues. Here is sample code using ClientWebSocket in .NET Core or .NET 5+:

using System;
using System.Net.WebSockets;
using System.Threading;
using System.Threading.Tasks;

class Program
{
    static async Task Main(string[] args)
    {
        using (ClientWebSocket webSocket = new ClientWebSocket())
        {
            try
            {
                Uri serverUri = new Uri("ws://yourserveruri");
                await webSocket.ConnectAsync(serverUri, CancellationToken.None);
                Console.WriteLine("Connected!");

                // Send and receive data here

                await webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, "Closing", CancellationToken.None);
                Console.WriteLine("Closed!");
            }
            catch (WebSocketException e)
            {
                Console.WriteLine($"WebSocketException: {e.Message}");
            }
            catch (Exception e)
            {
                Console.WriteLine($"Exception: {e.Message}");
            }
        }
    }
}

Your answer

Viorel 122.5K Reputation points

2024-06-18T04:55:47.2066667+00:00

Maybe the server returns a response, which is unsupported in .NET Framework:

https://github.com/websocket-client/websocket-client/issues/626

Check if it works using .NET 7 or 8.
Anonymous

2024-07-10T07:35:40.21+00:00

Use .NET Core or .NET 5+

If possible, migrate to .NET Core or .NET 5+, as these versions have better support for WebSocket and fewer issues. Here is sample code using ClientWebSocket in .NET Core or .NET 5+:

using System; using System.Net.WebSockets; using System.Threading; using System.Threading.Tasks; class Program { static async Task Main(string[] args) { using (ClientWebSocket webSocket = new ClientWebSocket()) { try { Uri serverUri = new Uri("ws://yourserveruri"); await webSocket.ConnectAsync(serverUri, CancellationToken.None); Console.WriteLine("Connected!"); // Send and receive data here await webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, "Closing", CancellationToken.None); Console.WriteLine("Closed!"); } catch (WebSocketException e) { Console.WriteLine($"WebSocketException: {e.Message}"); } catch (Exception e) { Console.WriteLine($"Exception: {e.Message}"); } } } }

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Error using ClientWebSocket: The 'Connection' header value 'Upgrade,Keep-Alive' is invalid. .NET Framework 4.7.2

Your answer