Socket issue in windows form. Socket stop replying when change tab control

Question

i've made some program that starts an asynchronous socket that handles all client request.

Socket starts before Form1 is called, and works fine

static class Program
{
    /// <summary>
    /// The main entry point for the application.
    /// </summary>
    [STAThread]
    static void Main()
    {
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        AsynchronousServer ascSv = new AsynchronousServer();
        Application.Run(new Form1());
        if (ascSv != null)
            ascSv.Stop();
    }
}

--Edited--- (Added AsynchronousServer.cs)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Server
{
    public class StateObject
    {
        // Client  socket.  
        public Socket workSocket = null;
        // Size of receive buffer.  
        public const int BufferSize = 1024;
        // Receive buffer.  
        public byte[] buffer = new byte[BufferSize];
        // Received data string.  
        public StringBuilder sb = new StringBuilder();
    }

    public class AsynchronousServer
    {
        public ManualResetEvent allDone = new ManualResetEvent(false);
        Socket listener;
        public Thread t;
        public AsynchronousServer()
        {
            t = new Thread(StartListening);
            t.Start();
        }

        public void Stop()
        {
            try
            {
                listener.Shutdown(SocketShutdown.Both);
                listener.Disconnect(false);
                try
                {
                    listener.Close();
                    listener.Dispose();
                }
                catch { }
            }
            catch
            {

            }
            if (t!=null &&t.IsAlive)
            {
                t.Abort();
                t = null;
            }
            listener = null;
        }

        public void StartListening()
        {
            // Establish the local endpoint for the socket.  
            // The DNS name of the computer  
            IPHostEntry ipHostInfo = Dns.GetHostEntry(Dns.GetHostName());
            IPAddress ipAddress = ipHostInfo.AddressList[0];
            IPEndPoint localEndPoint = new IPEndPoint(IPAddress.Parse("192.168.100.115"), 11000);

            // Create a TCP/IP socket.  
            listener = new Socket(AddressFamily.InterNetwork,
                SocketType.Stream, ProtocolType.Tcp);

            // Bind the socket to the local endpoint and listen for incoming connections.  
            try
            {
                listener.Bind(localEndPoint);
                listener.Listen(100);

                while (true)
                {
                    // Set the event to nonsignaled state.  
                    allDone.Reset();

                    // Start an asynchronous socket to listen for connections.  
                    //Console.WriteLine("Waiting for a connection...");
                    listener.BeginAccept(
                        new AsyncCallback(AcceptCallback),
                        listener);

                    // Wait until a connection is made before continuing.  
                    allDone.WaitOne();
                }

            }
            catch
            {
                //MessageBox.Show(e.Message);
            }
        }

        public void AcceptCallback(IAsyncResult ar)
        {
            try
            {
                // Signal the main thread to continue.  
                allDone.Set();

                // Get the socket that handles the client request.  
                Socket listener = (Socket)ar.AsyncState;
                Socket handler = listener.EndAccept(ar);

                // Create the state object.  
                StateObject state = new StateObject();
                state.workSocket = handler;
                handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
                    new AsyncCallback(ReadCallback), state);
            }
            catch
            {

            }

        }

        public void ReadCallback(IAsyncResult ar)
        {
            try
            {
                String content = String.Empty;

                // Retrieve the state object and the handler socket  
                // from the asynchronous state object.  
                StateObject state = (StateObject)ar.AsyncState;
                Socket handler = state.workSocket;

                // Read data from the client socket.   
                int bytesRead = handler.EndReceive(ar);

                if (bytesRead > 0)
                {
                    // There  might be more data, so store the data received so far.  
                    state.sb.Append(Encoding.ASCII.GetString(
                        state.buffer, 0, bytesRead));

                    // Check for end-of-file tag. If it is not there, read   
                    // more data.  
                    content = state.sb.ToString();
                    if (content.IndexOf("<EOF>") > -1)
                    {
                        // All the data has been read from the   
                        // client. Display it on the console.  
                        //Console.WriteLine("Read {0} bytes from socket. \n Data : {1}",content.Length, content);
                        // Echo the data back to the client.

                        //Choose what to do with the packet
                        string callBack= ClientController.GenerateResponseTo(content);
                        //Choose what server has to reply to client
                        Send(handler, @callBack+"*<EOF>");
                        //Send(handler, @"N:\tmp\2parts\save.cnf*1*<EOF>");
                    }
                    else
                    {
                        // Not all data received. Get more.  
                        handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
                        new AsyncCallback(ReadCallback), state);
                    }
                }
            }
            catch { }

        }

        private void Send(Socket handler, String data)
        {
            try
            {
                // Convert the string data to byte data using ASCII encoding.  
                byte[] byteData = Encoding.ASCII.GetBytes(data);

                // Begin sending the data to the remote device.  
                handler.BeginSend(byteData, 0, byteData.Length, 0,
                    new AsyncCallback(SendCallback), handler);
            }
            catch { }
        }

        private void SendCallback(IAsyncResult ar)
        {
            try
            {
                // Retrieve the socket from the state object.  
                Socket handler = (Socket)ar.AsyncState;

                // Complete sending the data to the remote device.  
                int bytesSent = handler.EndSend(ar);
                //Console.WriteLine("Sent {0} bytes to client.", bytesSent);

                handler.Shutdown(SocketShutdown.Both);
                handler.Close();

            }
            catch
            {
            }
        }


    }
}

Once i'm on GUI clients can connect to server to ask for they answer and server replies an sleep packet untill user inputs a valid path on GUI and clicks START.

Well that also works fine.

My issue is that when a client is succesfully conected it starts sending a callback to the server and server outputs its callback in a progressbar from a custom control i've made and that also "works" but the issue is:

If i keep the GUI on the server start tab. All works fine, clients get their answers and server adds and updates client's progress bar. BUT when i change the tab controll to the tab where the progress bar of all clients are displayed, server stops sending any replys to clients. Even if i go back to the server start tab it doesn't reply anymore.

I'm so hardstuck on this. Does anyone know where does my error come from?

I also upladed some pictures of a debug client and my issue:

Client connected to server and getting answers:

Changeing GUI tab and server stopping:

Answer 1

Problem solved. Thanks to Aram Kocharyan and Mong Zhu.

The error was that I was trying to access a GUI element from a different thread. To modify a GUI element from another thread must use Invoke method of controll (Invoke calls the method from the thread that owns the component)

Example:

Form1.GetInstance.flowLayoutPanel_progress.Invoke(
                new Action(() => Parse0(splited[1], out toReturn)));