Program that demonstrates HttpRequestException from HttpClient.PostAsync after Keep-Alive timeout

nginx_template.conf

daemon off;
master_process off;

error_log  THIS_PATH/logs/error.log;
pid        THIS_PATH/logs/nginx.pid;

events {
  worker_connections 1024;
}

http {
  default_type application/octet-stream;
  log_format   main '$remote_addr - $remote_user [$time_local]  $status '
    '"$request" $body_bytes_sent "$http_referer" '
    '"$http_user_agent" "$http_x_forwarded_for"';
  access_log                 THIS_PATH/logs/access.log  main;
  client_body_temp_path      THIS_PATH/tmp/client_body_temp;
  proxy_temp_path            THIS_PATH/tmp/proxy_temp;
  fastcgi_temp_path          THIS_PATH/tmp/fastcgi;
  uwsgi_temp_path            THIS_PATH/tmp/uwsgi;
  scgi_temp_path             THIS_PATH/tmp/scgi;

  keepalive_timeout 1;

  server {
    listen 8001;
    root THIS_PATH/http_root;
  }
}

Program.cs

namespace HttpClientTest
{
    using System;
    using System.Collections.Generic;
    using System.Net.Http;
    using System.Threading;

    class Program
    {
        static void Main(string[] args)
        {
            using (var httpClient = new HttpClient())
            {
                try
                {
                    var formData = new FormUrlEncodedContent(new Dictionary<string, string> { });
                    var r = httpClient.PostAsync($"http://127.0.0.1:8001/123.txt?first", formData).Result.Content.ReadAsStringAsync().Result;
                    Console.WriteLine(r);
                    Thread.Sleep(TimeSpan.FromSeconds(1.5));
                    var r2 = httpClient.PostAsync($"http://127.0.0.1:8001/123.txt?second", formData).Result.Content.ReadAsStringAsync().Result;
                    Console.WriteLine(r2);
                }
                catch (Exception e)
                {
                    Console.WriteLine(e);
                }
            }
        }
    }
}

Program_NetworkStreamSyncCompleted.cs

using System;

namespace TcpTest
{
    using System.Net;
    using System.Net.Sockets;
    using System.Threading;
    using System.Threading.Tasks;

    class Program
    {
        static void Main(string[] args)
        {
            var listener = new TcpListener(IPAddress.Any, 8001);
            listener.Start();
            var endpoint = (IPEndPoint) listener.LocalEndpoint;
            Console.WriteLine($"Endpoint: {endpoint}");
            
            var t = new Thread(() =>
            {
                try
                {
                    while (true)
                    {
                        var socket = listener.AcceptSocket();
                        Console.WriteLine($"Accepted: {socket.RemoteEndPoint}");
                        socket.Shutdown(SocketShutdown.Both);
                        socket.Close();
                        socket.Dispose();
                    }
                }
                catch (Exception e)
                {
                    Console.WriteLine($"Acceptor: stop");
                }
            })
            {
                IsBackground = true,
                Name = "Acceptor"
            };
            t.Start();
            
            var client = new TcpClient();
            client.Connect(IPAddress.Loopback, endpoint.Port);
            Console.WriteLine($"Connected: {client.Client.LocalEndPoint}");
            
            Thread.Sleep(1000);
            Console.WriteLine($"Slept");
            
            var clientStream = new NetworkStream(client.Client);
            var clientReadTask = clientStream.ReadAsync(new byte[256], 0, 256);
            Console.WriteLine($"IsSyncCompleted initial: {clientReadTask.IsCompleted}");
            Thread.Sleep(100);
            Console.WriteLine($"Slept");
            Console.WriteLine($"IsSyncCompleted after sleep: {clientReadTask.IsCompleted}");
            Console.WriteLine($"ReadAsync result: {clientReadTask.Result}");
            
            listener.Stop();
        }
    }
}

run_nginx.sh

#!/bin/bash
set -e
set -u
set -o pipefail
cd "$(dirname "$0")"
mkdir -p http_root logs tmp
THIS_PATH=$(pwd)
cat nginx_template.conf | sed -e "s%THIS_PATH%${THIS_PATH}%g" > nginx.conf
nginx -c $(pwd)/nginx.conf