//TelnetConnection stopConnection = new TelnetConnection();
public partial class BarcodeReceivingForm : Form
{
    //GLOBAL VARIABLES
    const string Hostname = "myip";
    private const int Port = 23;


    public BarcodeReceivingForm()
    {
        InitializeComponent();
    }

    private void btn_ConnectT_Click(object sender, EventArgs e)
    {

        var readData = new TelnetConnection(Hostname, Port);
        readData.ServerSocket(Hostname, Port);

    }

    private void btn_StopConnection_Click(object sender, EventArgs e)
    {
        //var connection = new TelnetConnection(Hostname, Port);
       // connection.CloseConnection();
    }
}

private Thread _readWriteThread;
    private TcpClient _client;
    private NetworkStream _networkStream;
    private string _hostname;
    private int _port;

    public TelnetConnection(string hostname, int port)
    {
        this._hostname = hostname;
        this._port = port;
    }

    public void ServerSocket(string ip, int port)
    {

        try
        {
            _client = new TcpClient(ip, port);
        }
        catch (SocketException)
        {
            MessageBox.Show(@"Failed to connect to server");
            return;
        }

        //Assign networkstream
        _networkStream = _client.GetStream();

        //start socket read/write thread
        _readWriteThread = new Thread(ReadWrite);
        _readWriteThread.Start();
    }

    public void ReadWrite()
    {

        //Set up connection loop
        while (true)
        {
            var command = "test";
            if (command == "STOP1")
                break;

            //write(command);
             var received = Read();


            BcForm.lst_BarcodeScan.Invoke(new Action (() => BcForm.lst_BarcodeScan.Items.Add(received)));


        }

    }

    public string Read()
    {
        byte[] data = new byte[1024];
        var received = "";

        var size = _networkStream.Read(data, 0, data.Length);
        received = Encoding.ASCII.GetString(data, 0, size);

        return received;
    }

    public void CloseConnection()
    {
        _networkStream.Close();
        _client.Close();
    }
}