带有 .Net Core 2.1 的 HttpClient 挂起 [英] HttpClient with .Net Core 2.1 hangs

问题描述

鉴于以下 .Net Core 2.1 控制台应用程序...

Given the following .Net Core 2.1 Console App...

using System;
using System.Diagnostics;
using System.Net.Http;
using System.Net.Http.Headers;

namespace TestHttpClient
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                using (var httpClient = new HttpClient())
                {
                    httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));                    

                    string url = "https://jsonplaceholder.typicode.com/posts/1";
                    var response = httpClient.GetAsync(url).Result;
                    string jsonResult = response.Content.ReadAsStringAsync().Result;   
                }
            }
            catch (Exception ex)
            {
                Debug.WriteLine(ex.ToString());
            }
        }
    }
}

对 GetAsync 的调用挂起并引发异常并显示以下消息:

The call to GetAsync hangs throwing an exception with the following message:

System.Net.Http.HttpRequestException:连接尝试失败因为关联方在一段时间后没有正确回应时间，或建立的连接失败，因为连接的主机已未能响应 ---> System.Net.Sockets.SocketException: A连接尝试失败，因为连接方没有正确一段时间后响应，或建立连接失败因为连接的主机没有响应

System.Net.Http.HttpRequestException: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond ---> System.Net.Sockets.SocketException: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond

但是，切换到 .Net Core 2.0 并且它工作正常...

注意

我试过使用:

HttpClientFactory -> Same result
WebRequest        -> Same result

想法?

更新 1这在不在公司网络上时有效，这可能意味着代理的行为可能会发生变化.然而，不管怎样，core2.0 仍然可以工作.

UPDATE 1 This works when not on the corporate network which might mean a change in behavior with the proxy perhaps. However, core2.0 still works regardless so trying to find the difference.

更新 2看起来像是引入了一个错误并报告了...

UPDATE 2 Looks like a bug was introduced and it is reported...

https://github.com/dotnet/corefx/issues/30166#issuecomment-395489603

推荐答案

很明显，这里报告了一个错误/重大更改.

So apparently there is a bug/breaking change reported on this.

这里:https://github.com/dotnet/corefx/issues/30166https://github.com/dotnet/corefx/issues/30191

我认为是我遇到的两个独立但相关的问题.

Two separate but related issues that I believe is what I am experiencing.

不过，我找到了一种解决方法.

However, I found what appears to be a workaround.

using System;
using System.Diagnostics;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Threading.Tasks;

namespace TestHttpClient
{
    static class Program
    {
        static async Task Main(string[] args)
        {
            try
            {
                using (var httpClient = new HttpClient(new WinHttpHandler() { WindowsProxyUsePolicy = WindowsProxyUsePolicy.UseWinInetProxy }))
                {
                    httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

                    string url = "https://jsonplaceholder.typicode.com/posts/1";                   

                    var response = await httpClient.GetAsync(url);
                    string jsonResult = await response.Content.ReadAsStringAsync();
                }
            }
            catch (Exception ex)
            {
                Debug.WriteLine(ex.ToString());
                throw;
            }
        }
    }
}

这里的关键部分是使用WinHttpHandler并将WindowsProxyUsePolicy设置为WindowsProxyUsePolicy.UseWinInetProxy

The key part here is to use WinHttpHandler and set the WindowsProxyUsePolicy to WindowsProxyUsePolicy.UseWinInetProxy

WinHttpHandler 是通过添加 nuget 包 System 找到的.Net.Http.WinHttpHandler

WinHttpHandler is found by adding nuget package System.Net.Http.WinHttpHandler

这篇关于带有 .Net Core 2.1 的 HttpClient 挂起的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！