While loop make crash

// include <Stdio.H>와 같이 System 라이브러리 사용 선언.
using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Windows.Forms;
using System.Threading;
using System.Threading.Tasks;
using Packet;

namespace WindowsFormsApp16  // Form의 이름
{
    
    public partial class Form1 : Form
    {

        UdpClient Client = new UdpClient(19000); //PORT NUMBER
        Byte[] sendBytes = Encoding.ASCII.GetBytes("Broad");

        string data = " ";

        public Form1()
        {
          InitializeComponent();
        }

        private void textBox2_TextChanged(object sender, EventArgs e)
        {
            textBox2.SelectionStart = textBox2.Text.Length;
        }

        //버튼 1의 설정
        private void button1_Click(object sender, EventArgs e)
        {
            try
            {

                UdpClient cli = new UdpClient();

                string msg = "Broad";

                byte[] datagram = Encoding.ASCII.GetBytes(msg);
                cli.Send(datagram, datagram.Length, "192.168.1.100", 19000);

               while(true)
              {
               IPEndPoint epRemote = new IPEndPoint(IPAddress.Any, 0);
               byte[] bytes = cli.Receive(ref epRemote);



               // 계속 데이터를 불러와야함. 
               textBox1.Text = "[Send] 192.168.1.100 로 " + datagram.Length + " 바이트 전송\r\n"
                      + "[Send]" + Encoding.UTF8.GetString(datagram) + "\r\n[receive]" + BitConverter.ToString(bytes);
               }

            }


            catch (Exception ex)
            {
                textBox1.Text += ex.Message.ToString();
            }

        }

        //버튼 2의 설정 지정한 수치 출력
        private void button2_Click(object sender, EventArgs e)
        {
            try
            {

                string str = textBox1.Text;
                string SubStr = str.Substring(161, 4);
                string message = string.Empty;

                textBox2.Text = SubStr;

            }
          
            catch
            {
                string message = string.Empty;
                message = string.Format("check conncet");
                MessageBox.Show(message);
            }
        }

        //버튼 3 클릭시 Broad 를 장비로 전달
        private void button3_Click(object sender, EventArgs e)
        {

            try
            {

                textBox1.Clear();
               
            }


            catch
            {
                string message = string.Empty;
                message = string.Format("check conncet");
                MessageBox.Show(message);
            }
            

        }


            //장비에서 들어온 데이터를 Hex 데이터로 변환

            public static string ToHexString(string str)
            {
            var sb = new StringBuilder();

            var bytes = Encoding.Unicode.GetBytes(str);
            foreach (var t in bytes)
            {
                sb.Append(t.ToString("X2"));
            }

            return sb.ToString(); 
             }


        //UDP IP의 선언 및 String to Hex 데이터 출력 

        void recv(IAsyncResult res)
        {

            //Socket sock = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Udp);
            //var ep = new IPEndPoint(IPAddress.Parse("192.168.1.100"), 19000);


            UdpClient Client = new UdpClient(); //PORT NUMBER
            IPEndPoint src_ip = new IPEndPoint(IPAddress.Parse("192.168.1.100"), 19000);
            byte[] received = Client.EndReceive(res, ref src_ip);
            data = Encoding.UTF8.GetString(received);


            
            Byte[] sendBytes = Encoding.ASCII.GetBytes("Broad");

         

            // to avoid cross-threading we use Method Invoker
            this.Invoke(new MethodInvoker(delegate
            {

                textBox1.Clear();
                string str = "";

                for (int i = 0; i < 100; i++)
                {
                    str += ToHexString(data.Substring(i, 1)) + " ";
                }

                textBox1.Text = str;

                string str01 = data.Substring(0, 1); //@
                string str02 = data.Substring(1, 1); //F
               
                if ((str01 == "@") && (str02 == "F"))
                {
                    string strHR = data.Substring(2, 1);
                    Int64 Hr_Data = 0;

                    //label1.Text = Hr_Data.ToString();
                }

                //  Int64 Value = 0;
                //    Value = Convert.ToString(data.Substring(2, 1)), 16);
                //  label1.Text = Value.ToString();

            }));

            Client.BeginReceive(new AsyncCallback(recv), null);
        }


    


        private void textBox2_KeyDown(object sender, KeyEventArgs e)
        {

        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {

        }

        private void textBox3_TextChanged(object sender, EventArgs e)
        {

        }

        private void textBox2_TextChanged_1(object sender, EventArgs e)
        {

        }
    }
}