Xamarin.forms Mac 连接在尝试连接到本地主机服务器时被拒绝

Question

In my project I have to deserialize a list of Object Products that I have to get from a localhost server. However every time I try to get that data using HttpClient() I get a connection refused exception, which leads to another exception because now I have a null list.

I am able to see the serialize list in my localhost(https://localhost:5002/controller/Getall), I am just trying to deserialize this list from the API to my application.

The message is: Connection refused and the e.getBaseExeption is: Java.Net.ConnectionExecption

How can I get my connection to actually connect?

App.xaml.cs in application

public App()
        {
            InitializeComponent();

            var handler = new WebRequestHandler();
            try
            {
                
                List<Product> test = JsonConvert.DeserializeObject<List<Product>>(handler.Get("https://localhost:5002/controller/GetAll").Result);
                foreach (Product x in test)
                {
                    Console.WriteLine(x.Name);
                }
            }
            catch (Exception e)
            {
                Console.WriteLine("e message: " + e.Message);
            }

WebRequestHandler in application

public class WebRequestHandler
    {
        private HttpClient Client { get; }
        public WebRequestHandler()
        {
            Client = new HttpClient();
        }
        public async Task<string> Get(string url)
        {
            try
            {
                using (var client = new HttpClient())
                {
                    var response = await client.GetStringAsync(url).ConfigureAwait(false);
                    return response;
                }
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message + " " + e.GetBaseException());
               
            }


            return null;
        }

        public async Task<string> Post(string url, object obj)
        {
            using (var client = new HttpClient())
            {
                using (var request = new HttpRequestMessage(HttpMethod.Post, url))
                {
                    var json = JsonConvert.SerializeObject(obj);
                    using (var stringContent = new StringContent(json, Encoding.UTF8, "application/json"))
                    {
                        request.Content = stringContent;

                        using (var response = await client
                            .SendAsync(request, HttpCompletionOption.ResponseHeadersRead)
                            .ConfigureAwait(false))
                        {
                            if (response.IsSuccessStatusCode)
                            {
                                return await response.Content.ReadAsStringAsync();
                            }
                            return "ERROR";
                        }
                    }
                }
            }
        }
    }

InventoryController

[ApiController]
    [Route("Controller")]
    public class InventoryController : ControllerBase
    { 

        [HttpGet("GetAll")]
        public ActionResult<List<Product>> Get()
        {
            return Ok(DataContext.Inventory);
        }

    }

DataContext.cs

public class DataContext
    {
            public static List<Product> Inventory = new List<Product>
            {
                new ProductByQuantity(2.00, 20, "Ketchup", "Canned & Packaged Foods", 0002),
                new ProductByQuantity(2.00, 35, "Mayonnaise", "Canned & Packaged Foods", 0003),
                new ProductByQuantity(5.00, 25, "Chocolate bar", "Canned & Packaged Foods", 0004),
                new ProductByQuantity(3.50, 100, "Paper Towels", "Miscellaneous Kitchen Items", 0005),
                new ProductByQuantity(2.35, 80, "Plastic Wrap", "Miscellaneous Kitchen Items", 0006),
                new ProductByQuantity(1.50, 90, "Yougurt", "Refrigerated Foods", 0007),
                new ProductByQuantity(1.25, 150, "Bagels", "Bakery", 0008),
                new ProductByQuantity(1.00, 200, "Bread", "Bakery", 0009),
                new ProductByQuantity(3.50, 45, "Cereal", "Breakfast", 0010),
        };
    }

Answer 1

You have to remember that localhost refers to the machine at hand. In this case if you say localhost:5002 you are telling the device to go to port 5002 and go to that URL which of course won't exist.

What you need is some sort of tunnel like ngrok ( https://ngrok.com/ ). This way instead of calling localhost you will instead pass your ngrok url that runs on the machine that hosts the API and this way it will make that localhost API visible to the outside world.

However, if it is an Android (I ask because I see your exception mentioned Java) if you use 10.0.2.2 (If that one doesn't work try 0.0.0.0 ) that is the local callback it has and it should be able to connect to your localhost if you use that IP.

Again though, the preferred approach would be some sort of tunnel