正在检测服务器c#断开客户端连接

我已经使用线程和套接字为服务器和多个客户端编写了代码。通常情况下，客户端通过向服务器发送"exit"关键字来退出，但我希望服务器也能检测到客户端在没有向服务器发送"exit"关键字的情况下强行退出的情况，例如，当用户在向服务器发送消息的过程中按下客户端窗口的十字按钮时。我想要的是服务器应该检测到这种情况，并显示一些错误代码，然后继续接收来自连接到它的其他客户端的消息

我面临的第二个问题是，即使有多个客户端连接到服务器，我如何断开服务器连接。在我的代码中，我使用tcpListener.Stop（），但当我使用此方法时，会显示错误消息"server failed to start at ipaddress"，打开的此类窗口的数量相当于服务器正在侦听的客户端的数量。例如，如果服务器正在监听1000个客户端，那么1000个这样的窗口将打开，显示前面提到的错误消息，从使用该软件的人的角度来看，这看起来不太好。那么我该如何处理这种情况呢？同样在这种情况下，如果客户端再次开始向服务器发送消息，那么即使我断开了服务器的连接，它也会开始接收消息。在用户重新启动服务器之前，服务器应保持断开连接。

以下是我的服务器代码。

namespace WindowsFormsApplication1
{
public partial class Form1 : Form
{
    // Constants IP address of server and maximum number of clients server can connect.
    static class Constants
    {
        public const string IP = "127.0.0.1";
        public const int No_Of_Clients = 2;
    }
    // server port number
    int port_number;
    static IPAddress ipAddress = IPAddress.Parse(Constants.IP);
    TcpListener tcpListener;
    public Form1()
    {
        InitializeComponent();
        button1.Click += button1_Click;
        button2.Click += button2_Click;
        //this.FormClosing += Form1_FormClosing;
    }
    //Socket socketForClient;
    private void button1_Click(object sender, EventArgs e)
    {
        if (String.IsNullOrEmpty(textBox1.Text.Trim()))
        {
            System.Windows.Forms.MessageBox.Show("Port Number Empty", "Error");
        }
        else
        {
            port_number = int.Parse(textBox1.Text);
            createserver(Constants.No_Of_Clients);
            serveripaddress();
            infoBox1.Text = string.Format("The server is now listening at port {0} at ip address {1}", port_number, Constants.IP);
            infoBox1.Text = infoBox1.Text + "'r'n" + string.Format("The server can listen to maximum {0} number of clients", Constants.No_Of_Clients);
        }
    }
// this code disconnects the server
    private void button2_Click(object sender, EventArgs e)
    {
        try
        {
            tcpListener.Stop();
        }
        catch (Exception f)
        {
            MessageBox.Show(f.Message);
        }
    }
    public void serveripaddress()
    {
        serverip.Text = "Server IP : " + Constants.IP;
        //serverport.Text = "Port Number : " + port.ToString();
    }
    // Starts server
    private void createserver(int no_of_clients)
    {
        tcpListener = new TcpListener(ipAddress, port_number);
        tcpListener.Start();
        for (int i = 0; i < no_of_clients; i++)
        {
            Thread newThread = new Thread(new ThreadStart(Listeners));
            newThread.Start();
        }
    } // end of createserver();
//listen to client receiving messages     
public void Listeners()
    {
        Socket socketForClient;
        try
        {
            socketForClient = tcpListener.AcceptSocket();
        }
        catch
        {
            System.Windows.Forms.MessageBox.Show(string.Format("Server failed to start at {0}:{1}", Constants.IP, port_number), "Error");
            return;
        }
        if (socketForClient.Connected)
        {
            //System.Windows.Forms.MessageBox.Show("hello");
            string string1 = string.Format("Client : " + socketForClient.RemoteEndPoint + " is now connected to server.");
            infoBox1.Text = infoBox1.Text + "'r'n" + string1;
            NetworkStream networkStream = new NetworkStream(socketForClient);
            System.IO.StreamWriter streamWriter = new System.IO.StreamWriter(networkStream);
            System.IO.StreamReader streamReader = new System.IO.StreamReader(networkStream);
            string theString = "";
            while (true)
            {
                try
                {
                    theString = streamReader.ReadLine();
                }
                catch (Exception e)
                {
                    MessageBox.Show(e.Message);
                }
               // if (streamReader.ReadLine() == null )
                //{
                  //  System.Windows.Forms.MessageBox.Show(string.Format("Server failed to start at {0}:{1}", Constants.IP, port_number), "Error");
               // }
                    if (theString != "exit")
                {
                    textBox2.Text = textBox2.Text + "'r'n" + "-----------------------------------------------------------------------------------";
                    string string2 = string.Format("Message recieved from client(" + socketForClient.RemoteEndPoint + ") : " + theString);
                    textBox2.Text = textBox2.Text + "'r'n" + string2;
                    // ASCII code for the message from client
                    string string3 = string.Format("ASCII Code for message is : ");
                    textBox2.Text = textBox2.Text + "'r'n" + string3;
                    string string4 = "";
                    foreach (char c in theString)
                    {
                        string4 += string.Format(System.Convert.ToInt32(c) + " ");
                    }
                    textBox2.Text = textBox2.Text + string4;
                    // Hex value of message from client
                    string hex = "";
                    foreach (char c in theString)
                    {
                        int tmp = c;
                        hex += String.Format("{0:x2}", (uint)System.Convert.ToUInt32(tmp.ToString()));
                    }
                    string string5 = string.Format("Hex Code for the message from client : " + hex);
                    textBox2.Text = textBox2.Text + "'r'n" + string5;
                    //sending acknowledgement to client
                    try
                    {
                        socketForClient.Send(new ASCIIEncoding().GetBytes("The string was recieved from Client(" + socketForClient.RemoteEndPoint + ") : " + theString));
                    }
                    catch (Exception e)
                    {
                        MessageBox.Show(e.Message);
                    }
                } // end of if loop
                // if exit from client
                else
                {
                    string string7 = string.Format("Client " + socketForClient.RemoteEndPoint + " has exited");
                    infoBox1.Text = infoBox1.Text + "'r'n" + string7;
                    break;
                }
            } // end of  while loop
            streamReader.Close();
            networkStream.Close();
            streamWriter.Close();
        } // end of if loop
        socketForClient.Close();
    }
}
}