Using Broadcast Packets to Advertise a Server

using System;
using System.Drawing;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;
using System.Windows.Forms;
class NewTcpChat : Form
{
  private static TextBox newText;
  private static ListBox results;
  private static ListBox hosts;
  private static Socket client;
  private static byte[] data = new byte[1024];
  public NewTcpChat()
  {
   Text = "New TCP Chat Program";
   Size = new Size(400, 380);
   
   Label label1 = new Label();
   label1.Parent = this;
   label1.Text = "Enter text string:";
   label1.AutoSize = true;
   label1.Location = new Point(10, 30);
   newText = new TextBox();
   newText.Parent = this;
   newText.Size = new Size(200, 2 * Font.Height);
   newText.Location = new Point(10, 55);
   results = new ListBox();
   results.Parent = this;
   results.Location = new Point(10, 85);
   results.Size = new Size(360, 10 * Font.Height);
   Label label2 = new Label();
   label2.Parent = this;
   label2.Text = "Active hosts";
   label2.AutoSize = true;
   label2.Location = new Point(10, 240);
   hosts = new ListBox();
   hosts.Parent = this;
   hosts.Location = new Point(10, 255);
   hosts.Size = new Size(360, 5 * Font.Height);
   Button sendit = new Button();
   sendit.Parent = this;
   sendit.Text = "Send";
   sendit.Location = new Point(220,52);
   sendit.Size = new Size(5 * Font.Height, 2 * Font.Height);
   sendit.Click += new EventHandler(ButtonSendOnClick);
   Button connect = new Button();
   connect.Parent = this;
   connect.Text = "Connect";
   connect.Location = new Point(295, 20);
   connect.Size = new Size(6 * Font.Height, 2 * Font.Height);
   connect.Click += new EventHandler(ButtonConnectOnClick);
   Button listen = new Button();
   listen.Parent = this;
   listen.Text = "Listen";
   listen.Location = new Point(295,52);
   listen.Size = new Size(6 * Font.Height, 2 * Font.Height);
   listen.Click += new EventHandler(ButtonListenOnClick);
   Thread fh = new Thread(new ThreadStart(findHosts));
   fh.IsBackground = true;
   fh.Start();
  }
  void ButtonListenOnClick(object obj, EventArgs ea)
  {
   results.Items.Add("Listening for a client...");
   Socket newsock = new Socket
    (AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
   IPEndPoint iep = new IPEndPoint(IPAddress.Any, 9050);
   newsock.Bind(iep);
   newsock.Listen(5);
   newsock.BeginAccept(new AsyncCallback(AcceptConn), newsock);
   Thread advertise = new Thread(new ThreadStart(srvrAdvertise));
   advertise.IsBackground = true;
   advertise.Start();
  }
  void ButtonConnectOnClick(object obj, EventArgs ea)
  {
   results.Items.Add("Connecting...");
   client = new Socket
    (AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
   string selectedhost = (string)hosts.SelectedItem;
   string[] hostarray = selectedhost.Split(':');
   IPEndPoint iep = new IPEndPoint(IPAddress.Parse(hostarray[1]), 9050);
   client.BeginConnect(iep, new AsyncCallback(Connected), client);
  }
  void ButtonSendOnClick(object obj, EventArgs ea)
  {
   byte[] message = Encoding.ASCII.GetBytes(newText.Text);
   newText.Clear();
   client.BeginSend(message, 0, message.Length, 0,
            new AsyncCallback(SendData), client);
  }
  void AcceptConn(IAsyncResult iar)
  {
   Socket oldserver = (Socket)iar.AsyncState;
   client = oldserver.EndAccept(iar);
   results.Items.Add("Connection from: " + client.RemoteEndPoint.ToString());
   Thread receiver = new Thread(new ThreadStart(ReceiveData));
   receiver.IsBackground = true;
   receiver.Start();
  }
  void Connected(IAsyncResult iar)
  {
   try
   {
     client.EndConnect(iar);
     results.Items.Add("Connected to: " + client.RemoteEndPoint.ToString());
     Thread receiver = new Thread(new ThreadStart(ReceiveData));
     receiver.IsBackground = true;
     receiver.Start();
   } catch (SocketException)
   {
     results.Items.Add("Error connecting");
   }
  }
  void SendData(IAsyncResult iar)
  {
   Socket remote = (Socket)iar.AsyncState;
   int sent = remote.EndSend(iar);
  }
  void ReceiveData()
  {
   int recv;
   string stringData;
   while (true)
   {
     recv = client.Receive(data);
     stringData = Encoding.ASCII.GetString(data, 0, recv);
     if (stringData == "bye")
      break;
     results.Items.Add(stringData);
   }
   stringData = "bye";
   byte[] message = Encoding.ASCII.GetBytes(stringData);
   client.Send(message);
   client.Close();
   results.Items.Add("Connection stopped");
   return;
  }
  void srvrAdvertise()
  {
   Socket server = new Socket(AddressFamily.InterNetwork,
                 SocketType.Dgram, ProtocolType.Udp);
   server.SetSocketOption(SocketOptionLevel.Socket,
               SocketOptionName.Broadcast, 1);
   IPEndPoint iep = new IPEndPoint(IPAddress.Broadcast, 9051);
   byte[] hostname = Encoding.ASCII.GetBytes(Dns.GetHostName());
   while (true)
   {
     server.SendTo(hostname, iep);
     Thread.Sleep(60000);
   }
  }
  void findHosts()
  {
   while (true)
   {
     Socket remoteHosts = new Socket(AddressFamily.InterNetwork,
                     SocketType.Dgram, ProtocolType.Udp);
     IPEndPoint iep = new IPEndPoint(IPAddress.Any, 9051);
     EndPoint ep = (EndPoint)iep;
     remoteHosts.Bind(iep);
     byte[] data = new byte[1024];
     int recv = remoteHosts.ReceiveFrom(data, ref ep);
     string stringData = Encoding.ASCII.GetString(data, 0, recv);
     string entry = stringData + ":" + ep.ToString();
     if (!hosts.Items.Contains(entry))
      hosts.Items.Add(""entry);
   }
  }
  public static void Main()
  {
   Application.Run(new NewTcpChat());
  }
}