How to send other data when connected socket TcpClient in WindowsForms using NetworkStream ?

Question

Hi msdn,
I have a connection that using tcpclient, to send and receive data between server and client . The application is written on the basis of Window Form, I have used BackgroundWorker to handle parallel running tasks. The program runs normally, it receives data from the client side and sends the data back to the client. I want to add a function to send content from textbox , it will be sent to the client from server in parallel during the connection between server and client. But when I add this, I get an error returning "Cannot access a disposed object. Object name: System.Net.Sockets.NetworkStream" at this line "stream.Write(msg_byte, 0, msg_byte.Length);" and data is not sent. What did I do wrong, can you point it out to me. This is my snipped code below

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Xml.Linq;
using static System.Windows.Forms.VisualStyles.VisualStyleElement;

namespace Server
{
    public partial class Form1 : Form
    {
        BackgroundWorker bw;
        static NetworkStream stream = null;

        public Form1()
        {
            InitializeComponent();

            bw = new BackgroundWorker();
            bw.WorkerReportsProgress = true;
            bw.WorkerSupportsCancellation = true;
            bw.DoWork += bw_DoWork;
            bw.ProgressChanged += bw_ProgressChanged;
            bw.RunWorkerCompleted += bw_RunWorkerCompleted;
        }

        private void _startServer(string _ip, int _port)
        {
            TcpListener server = null;
            try
            {
                server = new TcpListener(IPAddress.Parse(_ip), _port);
                server.Start();
                Byte[] bytes = new Byte[1024];
                String data = null;
                while (true)
                {
                    TcpClient client = server.AcceptTcpClient();
                    txt_log.Invoke((Action)(() =>
                    {
                        txt_log.AppendText(DateTime.Now.ToString() + " Connnected " + client.Client.RemoteEndPoint.ToString() + "\r\n");
                    }));
                    data = null;
                    NetworkStream stream = client.GetStream();
                    int i;
                    while ((i = stream.Read(bytes, 0, bytes.Length)) != 0)
                    {
                        data = Encoding.ASCII.GetString(bytes, 0, i);
                        txt_log.Invoke((Action)(() =>
                        {
                            txt_log.AppendText(DateTime.Now.ToString() + " Received: " + data + "\r\n");
                        }));
                     
                        data = data.ToUpper();
                        byte[] msg = Encoding.ASCII.GetBytes(data);
                        stream.Write(msg, 0, msg.Length);
						txt_log.Invoke((Action)(() =>
                        {
                            txt_log.AppendText(DateTime.Now.ToString() + " Sent: " + data + "\r\n");
                        }));                
                    }
                }
            }
            catch (SocketException ex)
            {
                MessageBox.Show("_startServer: " + ex.Message);
            }
        }

        void bw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            MessageBox.Show("completed");
        }

        void bw_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {
            if (!bw.CancellationPending)
            {
                MessageBox.Show("processing");
            }
        }

        void bw_DoWork(object sender, DoWorkEventArgs e)
        {
            _startServer("192.168.10.15", 4444);
            bw.ReportProgress(100);
        }

        private void bt_start_Click(object sender, EventArgs e)
        {
            if (bw.IsBusy)
            {
                bw.CancelAsync();
            }
            else
            {
                txt_log.Clear();
                bw.RunWorkerAsync();
            }
        }

        private void bt_stop_Click(object sender, EventArgs e)
        {
            bw.CancelAsync();
            if (stream != null)
            {
                stream.Dispose();
            }
        }

        private void bt_send_Click(object sender, EventArgs e)
        {
            string msg_send = txt_msg.Text;
            byte[] msg_byte = Encoding.ASCII.GetBytes(msg_send);
			
			while (true)
			{
				stream.Write(msg_byte, 0, msg_byte.Length);
				txt_log.Invoke((Action)(() =>
                {
                    txt_log.AppendText(DateTime.Now.ToString() + " Sent new data: " + msg_send + "\r\n");
                })); 
				
				string msg_receive = null;
				byte[] temp_byte = new byte[1024];
				stream.Read(temp_byte, 0, temp_byte.Length);
				msg_receive = Encoding.ASCII.GetString(temp_byte);
                txt_log.Invoke((Action)(() =>
                {
                    txt_log.AppendText(DateTime.Now.ToString() + " Received new data: " + msg_receive + "\r\n");
                }));
			}	
        }


    }
}

The situation is open connection to server from the client, on the one hand, always keep the connection from the server to the client by sending temporary data continuously, like the client side always sending "are you there?" , the server always replied "ok, here I am" when get signal data temp from client, this way is working good for me, no issue. On the other hand, I would like to have other signals sent from the server to the client according to what the user enters into the Textbox component, i just try and thinking the best way to do it.

Thanks you all.

Answer 1

Hi @brian crist , Welcome to Microsoft Q&A.

I once wrote a complete example about tcp connection and information transfer using NetworkStream.

You can refer to it in the link below.

Client Dissconnect or down

If you have any questions about this, please comment bellow.

Best Regards,

Jiale

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