Blazor WebAssembly use of ClientWebSocket

Index.razor

@page "/"
@using System.Net.WebSockets
@using System.Text
@using System.Threading
@implements IDisposable

<h1>Echo test</h1>
<h3>State: @webSocket.State</h3>

@if (webSocket.State == WebSocketState.Open)
{
    <form @onsubmit="@SendMessageAsync">
        Message: <input @bind="@message" />
        <button type="submit">Send</button>
    </form>

    <pre>@log</pre>
}

@code {
    CancellationTokenSource disposalTokenSource = new CancellationTokenSource();
    ClientWebSocket webSocket = new ClientWebSocket();
    string message = "Hello, websocket!";
    string log = "";

    protected override async Task OnInitializedAsync()
    {
        await webSocket.ConnectAsync(new Uri("wss://echo.websocket.org"), disposalTokenSource.Token);
        _ = ReceiveLoop();
    }

    async Task SendMessageAsync()
    {
        log += $"Sending: {message}\n";
        var dataToSend = new ArraySegment<byte>(Encoding.UTF8.GetBytes(message));
        await webSocket.SendAsync(dataToSend, WebSocketMessageType.Text, true, disposalTokenSource.Token);
    }

    async Task ReceiveLoop()
    {
        var buffer = new ArraySegment<byte>(new byte[1024]);
        while (!disposalTokenSource.IsCancellationRequested)
        {
            // Note that the received block might only be part of a larger message. If this applies in your scenario,
            // check the received.EndOfMessage and consider buffering the blocks until that property is true.
            // Or use a higher-level library such as SignalR.
            var received = await webSocket.ReceiveAsync(buffer, disposalTokenSource.Token);
            var receivedAsText = Encoding.UTF8.GetString(buffer.Array, 0, received.Count);
            log += $"Received: {receivedAsText}\n";
            StateHasChanged();
        }
    }

    public void Dispose()
    {
        disposalTokenSource.Cancel();
        _ = webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, "Bye", CancellationToken.None);
    }
}

Are you hitting a Serverless HTTP Trigger with SignalR Service with this implementation?

https://websocket.org is no longer available, long live Postman Raw Echo Socket Service. Read more here: Introducing Postman’s WebSocket Echo Service

To make this code work, do this:
On line 28, replace "wss://echo.websocket.org" with "wss://ws.postman-echo.com/raw"