what is problem in this code for multi threads

Question

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Windows.Forms;

using System.Net;

using System.Net.Sockets;

using System.Threading;

using System.IO;

using Serverfrn.AQDatabaseDataSetTableAdapters;

namespace Serverfrn

{

public partial class Serverfrm : Form

{

// var

private Thread getStudents;//Thread acquiring client connections

private TcpListener listener; // listen for client connection

// private Thread[] studentThreads; //Threads for client interaction

public List<Thread> Students_threads_list; // List that holds the game players threads

internal bool disconnected = false; // true if the server closes

public Socket socket;

StudentClient[] student_client_array;

StudentClient student_client;

Thread student_thread;

int students_counter = 0 ; // a counter for the students

public MyDataTableAdapter Adapter = new MyDataTableAdapter(); // setup connection with DataBase

public Serverfrm()

{

InitializeComponent();

}

private void Serverfrm_Load(object sender, EventArgs e)

{

DisplayMessage("Welcome Admin at Demo system ");

}

// delegate that allows method DisplayMessage to be called

// in the thread that creates and maintains the GUI

private delegate void DisplayDelegate(string message);

// method DisplayMessage sets displayTextBox's Text property

// in a thread-safe manner

internal void DisplayMessage(string message)

{

// if modifying displayTextBox is not thread safe

if (displayTextBox.InvokeRequired)

{

// use inherited method Invoke to execute DisplayMessage

// via a delegate

Invoke(new DisplayDelegate(DisplayMessage),

new object[] { message });

} // end if

else // OK to modify displayTextBox in current thread

displayTextBox.Text += message;

} // end method DisplayMessage

private void SetUp(object argument)

{

TcpClient client = (TcpClient)argument;

try

{

StreamReader reader = new StreamReader(client.GetStream());

StreamWriter writer = new StreamWriter(client.GetStream());

string s = String.Empty;

while (s == null)

{

writer.Write("From client -> " + s);

writer.WriteLine("From server -> " + s);

}

reader.Close();

writer.Close();

client.Close();

DisplayMessage("Closing client connection!");

}

catch (IOException)

{

Console.WriteLine("Problem with client communication. Exiting thread.");

}

finally

{

if (client != null)

{

client.Close();

}

}

}

// notify Students to stop Running

private void Serverfrm_FormClosing(object sender, FormClosingEventArgs e)

{

disconnected = true;

System.Environment.Exit(System.Environment.ExitCode);

}

private void button2_Click(object sender, EventArgs e)

{

AddQuestion frm = new AddQuestion();

frm.ShowDialog(this);

}

private void button1_Click(object sender, EventArgs e)

{

int port = int.Parse(textBox2.Text);

IPAddress address = IPAddress.Parse(textBox1.Text);

DisplayMessage("Server sarted");

TcpListener listener = null;

try

{

listener = new TcpListener( address, port );

DisplayMessage("\r\nlistener started...");

listener.Start();

DisplayMessage("\r\nMultiThreadedEchoServer started...");

while (true)

{

DisplayMessage("/r/nWaiting for incoming client connections.../r/n");

TcpClient client = listener.AcceptTcpClient();

DisplayMessage("/r/nAccepted new client connection.../r/n");

getStudents = new Thread(SetUp);

getStudents.Start(client);

}

}

catch (Exception ex)

{

MessageBox.Show(ex.ToString());

}

finally

{

if (listener != null)

{

listener.Stop();

}

}

}// end method Serverfrm_FormClosing

}

}