NancyFX on Krestrel - Response Stream Closed - nancy

Question

I'm attempting it make a simple proxy server that will try to stream back data from an IP camera (the IP camera doesn't honor OPTIONS and has some other issues!). I tried doing this using NancyFX and Krestrel with the following proxy module. The idea was to just get 1028 bytes of data in and write it to the output stream asynchronously until canceled.
Here is a sample Nancy Module:
using System.Net.Http;
using System.Net.Http.Headers;
using System.Threading;
using System.Threading.Tasks;
using Nancy;
namespace Server.Modules
{
public class Proxy : NancyModule
{
public Proxy() : base("api/proxy")
{
Get("/", ProxyPage);
}
private async Task<Response> ProxyPage(dynamic args, CancellationToken cancellationToken)
{
// Create HttpClient
using (var httpClient = new HttpClient()) // Make this global/cached and indexed by auth code
{
// Handle Authentication
var auth = string.Empty;
if (!string.IsNullOrEmpty(Request.Headers.Authorization) && Request.Headers.Authorization.Contains(" "))
auth = Request.Headers.Authorization.Split(' ')[1];
else if (!string.IsNullOrEmpty(Request.Query.authorization))
auth = Request.Query.authorization;
httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", auth);
// Create Proxy REsponse object
var proxyResponse = new Response();
// Get Async
HttpResponseMessage response = await httpClient.GetAsync(Request.Query["url"],
HttpCompletionOption.ResponseHeadersRead, cancellationToken);
// Set Content Type
proxyResponse.ContentType = response.Content.Headers.ContentType.ToString();
// Set Status Code
proxyResponse.StatusCode = (HttpStatusCode)(int)response.StatusCode;
// Handle stream writing
proxyResponse.Contents = async s =>
{
var result = response.Content.ReadAsStreamAsync();
var data = new byte[1028];
int bytesRead;
while (!cancellationToken.IsCancellationRequested && (bytesRead = await result.Result.ReadAsync(data, 0, data.Length, cancellationToken)) > 0)
{
await s.WriteAsync(data, 0, bytesRead, cancellationToken);
await s.FlushAsync(cancellationToken);
}
response.Dispose();
};
// Return Response container
return proxyResponse;
}
}
}
}
When I run it, I get through the while loop a couple times but then get an exception in FrameResponseStream (Krestrel): "System.ObjectDisposedException: 'Cannot access a disposed object.'" It appears that the stream is being closed (_state = FrameStreamState.Closed -- https://github.com/aspnet/KestrelHttpServer/blob/rel/2.0.0/src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/FrameResponseStream.cs) prematurely but I cannot figure out why or what I need to change to resolve it!

Answer 1

You should use ResponseContentRead instead of ResponseHeadersRead
HttpResponseMessage response = await httpClient.GetAsync(Request.Query["url"],
HttpCompletionOption.ResponseContentRead, cancellationToken);