How to connect and listen to external websocket url using C# and ASP.Net Core 2.2

Question

I am trying to create a bot which that listen to an WebSocket URL with C# and ASP.Net Core 2.2.

But I’m new in WebSocket area.

I read Microsoft documentation about WebSocket and ClientWebSocket to solve my problem. but there are not help to me.

How my app can listen to an external WebSocket URL and react to incoming messages ?

I tried below code but get "Cannot create an instance of the abstract class or interface 'WebSocket'." error.

using (var ws = new WebSocket("wss://ws.example.com"))
{
    ws.OnMessage += (sender, e) =>
        Console.WriteLine("Message received" + e.Data);
    ws.OnError += (sender, e) =>
        Console.WriteLine("Error: " + e.Message);
    ws.Connect();
        Console.ReadKey(true);
}

Answer 1

This should do it in the base case scenario.

 public class Listener
    {
        public void StopListening()
        {
            this.src.Cancel();
        }
        private Task listenTask;
        private CancellationTokenSource src=new CancellationTokenSource();
        public Task Listen(string url)
        {

           listenTask = Task.Run(async () =>
            {
                try
                {
                    byte[] buffer = new byte[1024];
                    await socket.ConnectAsync(new Uri(url), CancellationToken.None);
                    while (true)
                    {
                        WebSocketReceiveResult result = await socket.ReceiveAsync(buffer, CancellationToken.None);
                        string data = Encoding.UTF8.GetString(buffer, 0, result.Count);
                        Console.WriteLine(data);
                    }
                }
                catch (Exception ex)
                {
                    //treat exception
                }
            },src.Token);
        }
    }

However if you plan to create multiple Listener objects ( in the context of a HttpController that on a route opens sockets ) then things change.