Question

希望有人可以通过以下方式启发我。

我有一个客户端会向控制器端点发出请求（没有视图，c＃到c＃甚至是后来的C ++）。该控制器必须发送响应，因为它以json异步方式获取响应（将json1发送到客户端，然后发送json2，然后发送json3直到它关闭连接或发送空终止文本或类似文件）。目的是将结果流回客户端，以便在服务器仍然有效时开始处理。

我的控制器端点如下所示：

        [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();
        }

我的测试看起来像这样：

        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();
        }

我打电话给content.ReadAsStringAsync();

时出现异常

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()

编辑：异常是由于没有发送块的大小 await response.WriteAsync($"6\r\ntest {i}\r\n");

但是现在在测试/客户端，我立刻得到了所有的块...

Answer 1

为了解决这个问题，我使用了SSE或服务器端事件。这是asp.net核心中的服务器端：

        [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();
        }

这是客户端：

        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);
                }
            }
        }

使用ReadAsStringAsync强制等待所有消息以便继续。

asp.net Core 1.1的响应速度很快

1 个答案: