Asp.net Core 1.1 Answers

Question

Hope someone can enlighten me as follows.

I have a client that will make a request to the endpoint of the controller (no representation, C # to C # or even C ++ later). This controller will have to send responses as it retrieves them asynchronously as json (sends json1 to the client, then json2, then json3 until it closes the connection or sends null text or similar). The goal is to pass the results back to the client so that it can start processing while the server is still running.

My controller endpoint looks like this:

        [HttpGet("testStream")]
        public async Task testStream()
        {
            var response = HttpContext.Response;
            response.Headers[HeaderNames.TransferEncoding] = "chunked";


            for (var i = 0; i < 10; ++i)
            {
                await response.WriteAsync($"6\r\ntest {i}\r\n");

                await response.Body.FlushAsync();
                await Task.Delay(1 * 1000);
            }
            await response.WriteAsync("0\r\n\r\n");
            await response.Body.FlushAsync();
        }

My test is as follows:

        static async void DownloadPageAsync()
        {
            // ... Target page.
            string page = "http://localhost:8080/api/Stream/testStream";
            Console.WriteLine("test");
            while (!Debugger.IsAttached) Thread.Sleep(500);
            // ... Use HttpClient.
            using (HttpClient client = new HttpClient())
            using (var response = await client.GetAsync(page, HttpCompletionOption.ResponseHeadersRead))
            using (HttpContent content = response.Content)
            {
                string result = await content.ReadAsStringAsync();
                do
                {
                    Console.WriteLine(result);
                    result = await content.ReadAsStringAsync();
                }
                while (result != "null");
            }
            Console.WriteLine("END");
        }
        [Fact]
        public void Test1()
        {
            TestSurvey.DownloadPageAsync();
        }

I get an exception when I call content.ReadAsStringAsync();

System.Net.Http.HttpRequestException : Error while copying content to a stream.
[xUnit.net 00:01:14.5836121]       ---- System.IO.IOException : The read operation failed, see inner exception.
[xUnit.net 00:01:14.5836496]       -------- System.Net.Http.CurlException : Failure when receiving data from the peer
[xUnit.net 00:01:14.5846837]       Stack Trace:
[xUnit.net 00:01:14.5857807]            at System.Net.Http.HttpContent.<LoadIntoBufferAsyncCore>d__48.MoveNext()

EDIT: The exception occurred because you did not send the chunk size await response.WriteAsync($"6\r\ntest {i}\r\n");

/ ...

Answer 1

, SSE Server Side Events. asp.net:

        [HttpGet("testStream")]
        public async Task testStream()
        {
            var response = HttpContext.Response;
            response.StatusCode = 200;
            response.ContentType = "text/event-stream";

            for (var i = 0; i < 10; ++i)
            {
                //the tags are either 'events:' or 'data:' and two \n indicates ends of the msg
                //event: xyz \n\n
                //data: xyz \n\n
                await response.WriteAsync($"data: test {i}\n\n");

                response.Body.Flush();
                await Task.Delay(5 * 1000);
            }
            await response.WriteAsync("data:\n\n");
            await response.Body.FlushAsync();
        }

:

        string page = "http://localhost:8080/api/Stream/testStream";

        //while (!Debugger.IsAttached) Thread.Sleep(500);

        using (HttpClient client = new HttpClient())
        using (var s = await client.GetStreamAsync(page))
        {
            using (StreamReader r = new StreamReader(s))
            {
                string line = null;
                while (null != (line = r.ReadLine()))
                {
                    Console.WriteLine(line);
                }
            }
        }

ReadAsStringAsync , .