Proxy Blazor Server Application Websocket

I’m trying to proxy a Blazor Server Application. I have managed to proxy the initial page load and retrieve all static files. I cannot get the SignalR websocket connection to establish. Is this supported? The Websocket proxy definition is never triggered and I get 502 error codes on the _blazor?id=XXX websocket request

I have the following config:

app.UseProxies(proxies =>
{
    // SignalR Connection
    proxies.Map("ui/_blazor", proxy => proxy.UseWs((context, args) =>
        {
            var queryString = context.Request.QueryString;
            return $"{proxyUrl}/{args["endpoint"]}{queryString}";
        }));
    // Fallback
    proxies.Map("ui/{*endpoint}", proxy => proxy.UseHttp(
        (context, args) =>
        {
            var queryString = context.Request.QueryString;
            return $"{proxyUrl}/{args["endpoint"]}{queryString}";
        }, builder => builder.WithHttpClientName("proxyClient")));
});

/// services
.ConfigurePrimaryHttpMessageHandler(() => new HttpClientHandler
{
    // Disable Certificate Validation
    ServerCertificateCustomValidationCallback = (_, __, ___, ____) => true,
    UseDefaultCredentials = true
});

[twitchax]

It looks like, in the log, that the web server is interpreting this request as an http request.

Request starting HTTP/1.1 GET https://localhost:5003/ui/_blazor?id=KfqJrgcpG8oS2kD2e7uMoA

Did you “turn on” websocket support by using app.UseWebSockets();?

[georgearnall]

Apologies for not getting back to you, I’ve been pretty busy. This might be something I will come back to in the future. For now I have switch to WebAssembly and no longer require the proxy. Thanks for your help nonetheless.