Index.razor

@page "/"

@implements IDisposable

<h1>Streaming request / response</h1>

Type to send:
<input @bind="Input" @bind:event="oninput" />

You typed: @Message

@code {

    string Input
    {
        get => null;
        set
        {
            pipe.Writer.WriteAsync(System.Text.Encoding.UTF8.GetBytes(value));
        }
    }

    string Message { get; set; }

    readonly System.Threading.CancellationTokenSource cts = new System.Threading.CancellationTokenSource();
    readonly BrowserHttpHandler handler = new BrowserHttpHandler();
    readonly System.IO.Pipelines.Pipe pipe = new System.IO.Pipelines.Pipe();

    protected override void OnInitialized()
    {
        Task.Run(Send);
        Task.Run(Receive);
    }

    async Task Send()
    {
        try
        {
            using var request = new HttpRequestMessage(HttpMethod.Post, "/send?channel=123");
            request.Options.Set(BrowserHttpHandler.EnableStreamingRequest, true);
            request.SetBrowserRequestOption("allowHTTP1ForStreamingUpload", true);

            request.Content = new StreamContent(pipe.Reader.AsStream());

            using var response = await handler.SendAsync(request, cts.Token);
        }
        catch (Exception ex)
        {
            Message = ex.Message;
        }
    }

    async Task Receive()
    {
        var buffer = new byte[1024];

        try
        {
            using var request = new HttpRequestMessage(HttpMethod.Get, "/receive?channel=123");
            request.Options.Set(BrowserHttpHandler.EnableStreamingResponse, true);

            using var response = await handler.SendAsync(request, cts.Token);
            using var stream = await response.Content.ReadAsStreamAsync();

            int readCount;
            while ((readCount = await stream.ReadAsync(buffer)) > 0)
            {
                var str = System.Text.Encoding.UTF8.GetString(buffer, 0, readCount);

                Message += str;

                StateHasChanged();
            }
        }
        catch (Exception ex)
        {
            Message = ex.Message;
        }
    }

    public void Dispose()
    {
        cts.Cancel();
        cts.Dispose();
    }

}