Find if any error in this program.help me to build a robust app

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Net;
using System.Net.Sockets;
using System.Threading;
using System.Security;
using System.Runtime.InteropServices;
using System.Net.NetworkInformation;
using System.IO;

namespace WpfApplication4
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
       
        public void DoThisAllTheTime()
        {
            System.Windows.Threading.DispatcherTimer dispatcherTimer = new System.Windows.Threading.DispatcherTimer();
          
            dispatcherTimer.Stop();
            TcpClient tcpClient = new TcpClient();
            try
            {
                IPAddress ipaddr = IPAddress.Parse("xxx.xxx.x.xxx");
                int port = yyyy;
               IPEndPoint ipEndpt = new IPEndPoint(ipaddr, port);
                tcpClient.Connect(ipEndpt);
            }
            catch { }

            NetworkStream netStream = tcpClient.GetStream();

            if (netStream.CanWrite)
            {

                Byte[] sendBytes = Encoding.ASCII.GetBytes("username");
                netStream.Write(sendBytes, 0, sendBytes.Length);
                Byte[] sendBytes1 = Encoding.ASCII.GetBytes("password" + "\r\n");
                netStream.Write(sendBytes1, 0, sendBytes.Length);

            }
            else
            {
                MessageBox.Show("You cannot write data to this stream.");
                tcpClient.Close();
                // Closing the tcpClient instance does not close the network stream.
                netStream.Close();
                return;
            }
            Int32 bytes = 0;
            byte[] data = new byte[5100];
            Thread.Sleep(1000);
            if (netStream.CanRead && netStream.DataAvailable)
            {
                var sb = new StringBuilder();
             //   Thread.Sleep(1000);

                bytes = netStream.Read(data, 0, data.Length);
                string s = Encoding.ASCII.GetString(data, 0, bytes);
                sb.Append(s);
                richTextBox1.AppendText(sb.ToString());
          
                string subPath = "E:/here/output.txt";
             
                string subPath1 = "E:/here/";
                if (!Directory.Exists(subPath1))
                {
                    Directory.CreateDirectory(subPath1);
                }
                if (!File.Exists(subPath))
                {
                    File.Create(subPath);
                }
             
                System.IO.StreamWriter writer = new System.IO.StreamWriter(subPath); 
                writer.Write(s);
                writer.Close(); 
                writer.Dispose(); 
            }
            else
            {
                MessageBox.Show("You cannot read data from this stream and/or there is no data to read");
                tcpClient.Close();

                // Closing the tcpClient instance does not close the network stream.
                netStream.Close();
                return;
            }
            netStream.Close();
          //  System.Windows.Threading.DispatcherTimer dispatcherTimer1 = new System.Windows.Threading.DispatcherTimer();
            dispatcherTimer.Tick += new EventHandler(dispatcherTimer_Tick);
            dispatcherTimer.Interval = new TimeSpan(0, 0, 5);
            dispatcherTimer.Start();
        }
       
           
          

        private void dispatcherTimer_Tick(object sender, EventArgs e)
        {
            DoThisAllTheTime();
        }

        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            System.Windows.Threading.DispatcherTimer dispatcherTimer = new System.Windows.Threading.DispatcherTimer();
            dispatcherTimer.Tick += new EventHandler(dispatcherTimer_Tick);
            dispatcherTimer.Interval = new TimeSpan(0, 0, 5);
            dispatcherTimer.Start();
        }
    }
   
  
}