Tengo dos aplicaciones simples:

Una aplicación de servidor que espera en un puerto TCP específico para que un cliente se conecte. Luego escucha lo que dice, envía algunos comentarios y DESCONECTA a ese cliente.

Una aplicación de formulario que se conecta a la aplicación del servidor, luego dice algo, luego espera los comentarios y se desconecta del servidor, luego muestra los comentarios en el formulario.

Aunque la aplicación del servidor parece comportarse correctamente (lo he probado con Telnet y veo los comentarios y veo que la desconexión ocurre directamente después de los comentarios), sin embargo, la aplicación del formularioNo parece darse cuenta de la desconexión del servidor.. (TcpClient.Connected parece seguir siendo cierto incluso después de que el servidor se haya desconectado)

Mi pregunta es: ¿por qué TcpClient.Connected sigue siendo cierto y cómo puedo saber si / cuando el servidor se ha desconectado?

Aquí está mi código completo:

Solicitud de formulario:

using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Windows.Forms;
using System.Threading;

namespace Sender
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void sendButton_Click(object sender, EventArgs e)
        {
            TcpClient tcpClient = new TcpClient();
            tcpClient.Connect(IPAddress.Parse("127.0.0.1"), 81);
            responseLabel.Text = "waiting for response...";
            responseLabel.Invalidate();

            // write request
            NetworkStream networkStream = tcpClient.GetStream();
            byte[] buffer = (new ASCIIEncoding()).GetBytes("Hello World! ");
            networkStream.Write(buffer, 0, buffer.Length);
            networkStream.Flush();

            // read response
            Thread readThread = new Thread(new ParameterizedThreadStart(ReadResponse));
            readThread.Start(tcpClient);
        }

        void ReadResponse(object arg)
        {
            TcpClient tcpClient = (TcpClient)arg;
            StringBuilder stringBuilder = new StringBuilder();
            NetworkStream networkStream = tcpClient.GetStream();
            bool timeout = false;
            DateTime lastActivity = DateTime.Now;
            while (tcpClient.Connected && !timeout)
            {
                if (networkStream.DataAvailable)
                {
                    lastActivity = DateTime.Now;
                    while (networkStream.DataAvailable)
                    {
                        byte[] incomingBuffer = new byte[1024];
                        networkStream.Read(incomingBuffer, 0, 1024);
                        char[] receivedChars = new char[1024];
                        (new ASCIIEncoding()).GetDecoder().GetChars(incomingBuffer, 0, 1024, receivedChars, 0);
                        stringBuilder.Append(receivedChars);
                    }
                }
                else
                {
                    if (DateTime.Now > lastActivity.AddSeconds(60))
                        timeout = true;
                }
                System.Threading.Thread.Sleep(50);
            }
            Invoke((MethodInvoker)delegate
            {
                responseLabel.Text = "Response from Listener:\n" + stringBuilder.ToString();
                responseLabel.Invalidate();
            });

            if (timeout)
            {
                Console.Write("A timeout occured\n");
                networkStream.Close();
                tcpClient.Close();
            }
        }

    }
}

Aplicación de servidor:

using System.Net;
using System.Net.Sockets;
using System.Text;
using System;
using System.Threading;

namespace Listener
{
    class Program
    {
        static void Main(string[] args)
        {
            var tcpListener = new TcpListener(IPAddress.Any, 81);
            tcpListener.Start();
            Thread clientThread = new Thread(new ParameterizedThreadStart(Listen));
            clientThread.Start(tcpListener);
        }

        static void Listen(object arg)
        {
            TcpListener tcpListener = (TcpListener)arg;
            while (true)
            {
                TcpClient tcpClient = tcpListener.AcceptTcpClient();
                Thread clientThread = new Thread(new ParameterizedThreadStart(HandleClient));
                clientThread.Start(tcpClient);
            }
        }

        static void HandleClient(object arg)
        {
            TcpClient tcpClient = (TcpClient)arg;
            StringBuilder stringBuilder = new StringBuilder();
            ASCIIEncoding encoder = new ASCIIEncoding();
            DateTime lastActivity = DateTime.Now;

            // read request
            NetworkStream networkStream = tcpClient.GetStream();
            int timeout = 5; // gives client some time to send data after connecting
            while (DateTime.Now < lastActivity.AddSeconds(timeout) && stringBuilder.Length==0)
            {
                if (!networkStream.DataAvailable)
                {
                    System.Threading.Thread.Sleep(50);
                }
                else
                {
                    while (networkStream.DataAvailable)
                    {
                        lastActivity = DateTime.Now;
                        byte[] incomingBuffer = new byte[1024];
                        networkStream.Read(incomingBuffer, 0, 1024);
                        char[] receivedChars = new char[1024];
                        encoder.GetDecoder().GetChars(incomingBuffer, 0, 1024, receivedChars, 0);
                        stringBuilder.Append(receivedChars);
                    }
                }
            }
            string request = stringBuilder.ToString();

            // write response
            string response = "The listener just received: " + request;
            byte[] outgoingBuffer = encoder.GetBytes(response);
            networkStream.Write(outgoingBuffer, 0, outgoingBuffer.Length);
            networkStream.Flush();

            networkStream.Close();
            tcpClient.Close();
        }
    }

}