private void GetAllComputer()
        {
            DirectoryEntry root = new DirectoryEntry("WinNT:");
            foreach (DirectoryEntry dom in root.Children)
            {
                string name = dom.Name;
                this.comboBox1.Items.Add(name);
                foreach (DirectoryEntry com in dom.Children)
                {
                    if (com.SchemaClassName.Equals("Computer"))
                    {
                        string coms = com.Name;
                        comboBox2.Items.Add(coms);
                        IPHostEntry iphe = Dns.GetHostEntry(com.Name);
                        foreach (IPAddress ip in iphe.AddressList)
                        {
                            if(ip.AddressFamily==AddressFamily.InterNetwork)
                            comboBox3.Items.Add(ip.ToString());
                        }
                    }
                }
            }
        }

public void send(string message,string ip)
        {
            Socket s = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);

            
            IPAddress ipAddre = IPAddress.Parse(ip);

            Byte[] by = Encoding.UTF8.GetBytes(message);

            IPEndPoint ep = new IPEndPoint(ipAddre, 11000);

            s.SendTo(by, ep);

        }