Question

Situation:
1. Linux TCP server
2 Windows C# client application

The server receives messages from client, but when I try to send messages from server to the client nothing happens. When I disconnect I get the error:

“Unable to read data from the transport connection: A blocking operation was interrupted by a call to WSACancelBlockingCall.” and it points to the line —> string Response = swRead.ReadLine();

Here is the Client code:

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

namespace AsynClient
{
    public partial class Form1 : Form
    {

        private TcpClient client;
        private StreamWriter swSend;
        private StreamReader swRead;

        private bool connected = false;
        string bojaTekst = "", bojaPoz = "";


        private delegate void UpdateLogCallback(string strMessage);

        private Thread thrMessag;

        public Form1()
        {
            Application.ApplicationExit += new EventHandler(OnApplicationExit);
            InitializeComponent();
      }

        private void btnConnect_Click(object sender, EventArgs e)
        {
            if (connected == false)
            {
                InitializeConnection();
            }
            else
                MessageBox.Show("Vec je uspostavljenja konekcija.");
        }


        private void InitializeConnection()
        {
            client = new TcpClient();
            client.Connect("192.168.100.82", 3456);
            swSend = new StreamWriter(client.GetStream()); //prvo mora da se             konektuje, pa onda ova komanda



            thrMessag = new Thread(new ThreadStart(ReceiveMessages));
            thrMessag.Start();

            connected = true;
            btnSend.Enabled = true;
            btnDisconnect.Enabled = true;
            txtMsg.Enabled = true;
            btnConnect.Enabled = false;

        }

        private void UpdateLog(string strMessage)
        {

            txtServ.AppendText(strMessage + "\r\n");

        }

        private void ReceiveMessages()
        {
            swRead = new StreamReader(client.GetStream());

            string Response = swRead.ReadLine();

            while (connected)
            {

                // Show the messages in the log TextBox

                this.Invoke(new UpdateLogCallback(this.UpdateLog), new object[] {         swRead.ReadLine() });

            }
        }

        private void btnSend_Click(object sender, EventArgs e)
        {

            if (listBoxTekst.SelectedIndex == -1)
                listBoxTekst.SelectedIndex = 0;

            if (listBoxPozadina.SelectedIndex == -1)
                listBoxPozadina.SelectedIndex = 0;

            bojaTekst = listBoxTekst.Text;
        bojaPoz = listBoxPozadina.Text;


        SendMessage();
    }

    private void SendMessage()
    {
     txtMsg.Text);

        if (txtMsg.Lines.Length >= 1)
        {
            swSend.WriteLine(bojaPoz + "\t" + bojaTekst + "\t" + txtMsg.Text + "\t"); 
            swSend.Flush();                     
            txtMsg.Lines = null;                
        }                                       
        txtMsg.Text = "";
    }

    private void btnDisconnect_Click(object sender, EventArgs e)
    {
        char[] quit = new char[5];
        quit[0] = 'q'; quit[1] = 'w'; quit[2] = 'w'; quit[3] = 'w'; quit[4] = '\0';
        connected = false;

        btnConnect.Enabled = true;
        btnSend.Enabled = false;
        btnDisconnect.Enabled = false;
        txtMsg.Enabled = false;

        swSend.WriteLine(quit);
        swSend.Flush();

        swSend.Close();
        client.Close();
    }

    public void OnApplicationExit(object sender, EventArgs e)
    {
        if (connected == true)
        {
            connected = false;

            swSend.WriteLine("qwww"); //proveri da li radi f-ja kako treba
            swSend.Flush();

            swSend.Close();
            client.Close();
        }
    }      
}

}

The server side receives the messages with the read() function and it works fine, but when it sends with write() the C# client doesn’t receive the message.

Answer 1

Just one thing (there mioght be other problems):
You have a connected variable, which value you set to true, after you start your listening thread. The loop within the thread doesnt even run once.

thrMessag = new Thread(new ThreadStart(ReceiveMessages));   
thrMessag.Start();              
connected = true; //here is your first bug, should come before the previos line