A POP3 Client

using System;
using System.Drawing;
using System.IO;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;
using System.Windows.Forms;
class PopCheck       Form
{
  private TextBox hostname;
  private TextBox username;
  private TextBox password;
  private TextBox status;
  private ListBox messages;
  private TcpClient mailclient;
  private NetworkStream ns;
  private StreamReader sr;
  private StreamWriter sw;
  public PopCheck()
  {
   Text = "popcheck - A POP3 e-mail checker";
   Size = new Size(400, 380);
   Label label1 = new Label();
   label1.Parent = this;
   label1.Text = "Hostname:";
   label1.AutoSize = true;
   label1.Location = new Point(10, 33);
   hostname = new TextBox();
   hostname.Parent = this;
   hostname.Size = new Size(200, 2 * Font.Height);
   hostname.Location = new Point(75, 30);
   Label label2 = new Label();
   label2.Parent = this;
   label2.Text = "User name:";
   label2.AutoSize = true;
   label2.Location = new Point(10, 53);
   username = new TextBox();
   username.Parent = this;
   username.Size = new Size(200, 2 * Font.Height);
   username.Location = new Point(75, 50);
   Label label3 = new Label();
   label3.Parent = this;
   label3.Text = "Password:";
   label3.AutoSize = true;
   label3.Location = new Point(10, 73);
   password = new TextBox();
   password.Parent = this;
   password.PasswordChar = '*';
   password.Size = new Size(200, 2 * Font.Height);
   password.Location = new Point(75, 70);
   Label label4 = new Label();
   label4.Parent = this;
   label4.Text = "Status:";
   label4.AutoSize = true;
   label4.Location = new Point(10, 325);
  
   status = new TextBox();
   status.Parent = this;
   status.Text = "Not connected";
   status.Size = new Size(200, 2 * Font.Height);
   status.Location = new Point(50, 322);
   messages = new ListBox();
   messages.Parent = this;
   messages.Location = new Point(10, 108);
   messages.Size = new Size(360, 16 * Font.Height);
   messages.DoubleClick += new EventHandler(getmessagesDoubleClick);
   Button login = new Button();
   login.Parent = this;
   login.Text = "Login";
   login.Location = new Point(295, 32);
   login.Size = new Size(5 * Font.Height, 2 * Font.Height);
   login.Click += new EventHandler(ButtonloginOnClick);
   Button close = new Button();
   close.Parent = this;
   close.Text = "Close";
   close.Location = new Point(295, 62);
   close.Size = new Size(5 * Font.Height, 2 * Font.Height);
   close.Click += new EventHandler(ButtoncloseOnClick);
  }
  void ButtonloginOnClick(object obj, EventArgs ea)
  {
   status.Text = "Checking for messages...";
   Thread startlogin = new Thread(new ThreadStart(loginandretr));
   startlogin.IsBackground = true;
   startlogin.Start();
  }
  void ButtoncloseOnClick(object obj, EventArgs ea)
  {
   if (ns != null)
   {
     sw.Close();
     sr.Close();
     ns.Close();
     mailclient.Close();
   }
   Close();
  }
  void loginandretr()
  {
   string response;
   string from = null;
   string subject = null;
   int totmessages;
   try
   {
     mailclient = new TcpClient(hostname.Text, 110);
   } catch (SocketException)
   {
     status.Text = "Unable to connect to server";
     return;
   }
   ns = mailclient.GetStream();
   sr = new StreamReader(ns);
   sw = new StreamWriter(ns);
   response = sr.ReadLine(); //Get opening POP3 banner
   sw.WriteLine("User " + username.Text); //Send username
   sw.Flush();
   response = sr.ReadLine();
   if (response.Substring(0,3) == "-ER")
   {
     status.Text = "Unable to log into server";
     return;
   }
   sw.WriteLine("Pass " + password.Text); //Send password
   sw.Flush();
   try
   {
     response = sr.ReadLine();
   } catch (IOException)
   {
     status.Text = "Unable to log into server";
     return;
   }
   if (response.Substring(0,4) == "-ERR")
   {
     status.Text = "Unable to log into server";
     return;
   }
   sw.WriteLine("stat"); //Send stat command to get number of messages
   sw.Flush();
   response = sr.ReadLine();
   string[] nummess = response.Split(' ');
   totmessages = Convert.ToInt16(nummess[1]);
   if (totmessages > 0)
   {
     status.Text = "you have " + totmessages + " messages";
   } else
   {
     status.Text = "You have no messages" ;
   }
   for (int i = 1; i <= totmessages; i++)
   {
     sw.WriteLine("top " + i + " 0"); //read header of each message
     sw.Flush();
     response = sr.ReadLine();
     while (true)
     {
      response = sr.ReadLine();
      if (response == ".")
        break;
      if (response.Length > 4)
      {
        if (response.Substring(0, 5) == "From:")
         from = response;
        if (response.Substring(0, 8) == "Subject:")
         subject = response;
      }
     }
     messages.Items.Add(i + " " + from + " " + subject);
   }
  }
  void getmessagesDoubleClick(object obj, EventArgs ea)
  {
   string text = (string)messages.SelectedItem;
   string[] textarray = text.Split(' ');
   ShowMessage sm = new ShowMessage(ns, textarray[0]);
   sm.ShowDialog();
  }
  public static void Main()
  {
   Application.Run(new PopCheck());
  }
}
class ShowMessage : Form
{
  public ShowMessage(NetworkStream ns, string messnumber)
  {
   StreamReader sr = new StreamReader(ns);
   StreamWriter sw = new StreamWriter(ns);
   string response;
   Text = "Message " + messnumber;
   Size = new Size(400, 380);
   ShowInTaskbar = false;
   TextBox display = new TextBox();
   display.Parent = this;
   display.Multiline = true;
   display.Dock = DockStyle.Fill;
   display.ScrollBars = ScrollBars.Both;
   sw.WriteLine("retr " + messnumber); //Retrieve entire message
   sw.Flush();
   response = sr.ReadLine();
   while (true)
   {
     response = sr.ReadLine();
     if (response == ".")
      break;
     display.Text += response + "\r\n";
   }
  }
}