.NET Core reverse proxy middleware and signalR - asp.net

Question

I need to do a reverse proxy middleware in ASP.NET Core. I have something like this. But it doesn't work with SignalR.
Reverse proxy has address 192.168.187.72:5000; SignalR 192.168.187.62:5000. Client connects to proxy, proxy changes the url to SignalR hub url, but in client I always get this error:
The server disconnected before the handshake could be started
Code:
public ReverseProxyMiddleware(RequestDelegate nextMiddleware,ILogger<ReverseProxyMiddleware> logger)
{
_nextMiddleware = nextMiddleware;
_logger = logger;
}
public async Task Invoke(HttpContext context)
{
var targetUri = BuildTargetUri(context.Request);
if (targetUri != null)
{
var targetRequestMessage = CreateTargetMessage(context, targetUri);
using (var responseMessage = await _httpClient.SendAsync(targetRequestMessage, HttpCompletionOption.ResponseHeadersRead, context.RequestAborted))
{
context.Response.StatusCode = (int)responseMessage.StatusCode;
CopyFromTargetResponseHeaders(context, responseMessage);
await responseMessage.Content.CopyToAsync(context.Response.Body);
}
return;
}
await _nextMiddleware(context);
}
private HttpRequestMessage CreateTargetMessage(HttpContext context, Uri targetUri)
{
var requestMessage = new HttpRequestMessage();
CopyFromOriginalRequestContentAndHeaders(context, requestMessage);
requestMessage.RequestUri = targetUri;
requestMessage.Headers.Host = targetUri.Host;
requestMessage.Method = GetMethod(context.Request.Method);
return requestMessage;
}
private void CopyFromOriginalRequestContentAndHeaders(HttpContext context, HttpRequestMessage requestMessage)
{
var requestMethod = context.Request.Method;
var streamContent = new StreamContent(context.Request.Body);
requestMessage.Content = streamContent;
foreach (var header in context.Request.Headers)
{
requestMessage.Content?.Headers.TryAddWithoutValidation(header.Key, header.Value.ToArray());
}
}
private void CopyFromTargetResponseHeaders(HttpContext context, HttpResponseMessage responseMessage)
{
foreach (var header in responseMessage.Headers)
{
context.Response.Headers[header.Key] = header.Value.ToArray();
}
foreach (var header in responseMessage.Content.Headers)
{
context.Response.Headers[header.Key] = header.Value.ToArray();
}
context.Response.Headers.Remove("transfer-encoding");
}
private static HttpMethod GetMethod(string method)
{
if (HttpMethods.IsDelete(method)) return HttpMethod.Delete;
if (HttpMethods.IsGet(method)) return HttpMethod.Get;
if (HttpMethods.IsHead(method)) return HttpMethod.Head;
if (HttpMethods.IsOptions(method)) return HttpMethod.Options;
if (HttpMethods.IsPost(method)) return HttpMethod.Post;
if (HttpMethods.IsPut(method)) return HttpMethod.Put;
if (HttpMethods.IsTrace(method)) return HttpMethod.Trace;
return new HttpMethod(method);
}
private Uri BuildTargetUri(HttpRequest request)
{
Uri targetUri = null;
StringValues clientId = string.Empty;
targetUri = new Uri($"http://192.168.187.62:5000{request.Path}{request.QueryString}");
_logger.LogInformation($"Request URL {request.Host + request.Path + request.QueryString} Target URL {targetUri.ToString()}");
return targetUri;
}

Answer 1

Are you sure you want to create such functionality manually?
There are many great libraries for reverse proxying, Microsoft has a new project called YARP (https://microsoft.github.io/reverse-proxy/) which is an open source reverse proxy told to be high performance and highly customizable.
If you like I can show you a sample how you can use yarp in an ASP.NET Core app.