无法从UWP应用程序连接到localhost上托管的webservice

Question

我正在使用Xamarin Forms来处理Web服务。我制作了一个简单的Web服务，它托管在IIS Express上（VS 2015附带）。 Web服务处理员工信息。

最初使用Windows模拟器时效果很好。但我有问题让它与Android模拟器一起工作。求助于我从一个人那里得到了以下指示，

按照说明操作后，它不仅在Android模拟器中不起作用，而且UWP应用程序也停止工作。

以下是失败的地方

public class RestClient<T>
    {
        private const string WebServiceUrl = "http://localhost:52792/api/Employees/";
        //private const string WebServiceUrl = "http://services.groupkt.com/country/get/all/";

        public async Task<List<T>> GetAsync()
        {
            var httpClient = new HttpClient();
            httpClient.DefaultRequestHeaders.ExpectContinue = false;
            var json = "";
            try
            {

               **json = await httpClient.GetStringAsync(WebServiceUrl);
            }
            catch (HttpRequestException e)
            {
                var error = "";
                error=e.StackTrace;
                error = e.Source;
                error = e.HelpLink;
                error = e.ToString();


            }

            var taskModels = JsonConvert.DeserializeObject<List<T>>(json);

            return taskModels;
        }

以下是抛出的错误，

System.Net.Http.HttpRequestException: An error occurred while sending the request. ---> System.Runtime.InteropServices.COMException: The text associated with this error code could not be found.

A connection with the server could not be established

   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Net.Http.HttpHandlerToFilter.<SendAsync>d__4.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Net.Http.HttpClientHandler.<SendAsync>d__86.MoveNext()
   --- End of inner exception stack trace ---
   at System.Net.Http.HttpClientHandler.<SendAsync>d__86.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Net.Http.HttpClient.<FinishSendAsync>d__58.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Net.Http.HttpClient.<GetContentAsync>d__32`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at Plugin.RestClient.RestClient`1.<GetAsync>d__1.MoveNext()

我不知道这里出了什么问题。

更新

这在Windows和Windows Phone应用程序中仍然可以正常工作 UWP应用程序失败。

Answer 1

在您的RestClient类中，URL http://localhost:52792/api/Employees/指向设备的localhost，而不是托管IIS Express的计算机。

Answer 2

如果您的UWP应用尝试通过本地主机访问服务，请确认它具有环回豁免。

有关更多详细信息，请参见UWP Enable local network loopback。特别要注意的是，有些人发现环回豁免表可能已损坏，清除所有豁免并重新应用任何要求似乎都可以解决。

https://docs.microsoft.com/en-us/previous-versions/windows/apps/dn640582(v=win.10)