Tcp client Server C#

Question

I work on tcp client and server application. I have found in youtube this code. There are no have problem connection with tcp client and server, when i send to message it repeat infinity messagebox like you:you:you:you:.How can i fix this problem? The codes uses backgroundWorker ,it can cause repeat message. Can i solve the problem using Thread class ?

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Net;
using System.Net.Sockets;
using System.IO;

namespace WindowsFormsApp1
{

    public partial class Form1 : Form
    {
        private TcpClient client;
        public StreamReader STR;
        public StreamWriter STW;
        public string recieve;
        public String TextToSend;


        public Form1()
        {
            InitializeComponent();

            IPAddress[] localIP = Dns.GetHostAddresses(Dns.GetHostName());
            foreach (IPAddress address in localIP)
            {
                if (address.AddressFamily == AddressFamily.InterNetwork)
                {
                    textBoxServerIP.Text = address.ToString();
                }
            }
        }

        private void buttonStart_Click(object sender, EventArgs e)
        {
            TcpListener listener = new TcpListener(IPAddress.Any, int.Parse(textBoxServerPort.Text));
            listener.Start();
            client = listener.AcceptTcpClient();
            STR = new StreamReader(client.GetStream());
            STW = new StreamWriter(client.GetStream());
            STW.AutoFlush = true;

            backgroundWorker1.RunWorkerAsync();
            backgroundWorker2.WorkerSupportsCancellation = true;
        }

        private void buttonConnect_Click(object sender, EventArgs e)
        {
            client = new TcpClient();
            IPEndPoint IpEnd = new IPEndPoint(IPAddress.Parse(textBoxClientIP.Text), int.Parse(textBoxClientPort.Text));

            try
            {
                client.Connect(IpEnd);

                if (client.Connected)
                {
                    textBoxChatScreen.AppendText("Connected to server" + "\n");
                    STW = new StreamWriter(client.GetStream());
                    STR = new StreamReader(client.GetStream());
                    STW.AutoFlush = true;
                    backgroundWorker1.RunWorkerAsync();
                    backgroundWorker2.WorkerSupportsCancellation = true;

                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message.ToString());
            }
        }

        private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {
            while (client.Connected)
            {
                try
                {
                    recieve = STR.ReadLine();
                    this.textBoxChatScreen.Invoke(new MethodInvoker(delegate ()
                    {
                        textBoxChatScreen.AppendText("You:" + recieve + "\n");
                    }));
                    recieve = "";
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message.ToString());
                }
            }
        }

        private void backgroundWorker2_DoWork(object sender, DoWorkEventArgs e)
        {
            if (client.Connected)
            {
                STW.WriteLine (TextToSend);
                this.textBoxChatScreen.Invoke(new MethodInvoker(delegate ()
                {
                    textBoxChatScreen.AppendText("Me:" + TextToSend + "\n");
                }));
            }
            else
            {
                MessageBox.Show("Sending failed");
            }
            backgroundWorker2.CancelAsync();
        }

        private void buttonSend_Click(object sender, EventArgs e)
        {
            if (textBoxMessage.Text != "")
            {
                TextToSend = textBoxMessage.Text;
                backgroundWorker2.RunWorkerAsync();
            }
            textBoxMessage.Text = "";
        }
    }
}

I tried the code I can't run from the youtube video below.

https://www.youtube.com/watch?v=X16IyNbcAr0