Socket programming

yokzu

Hi.

I am trying to some socket programs. Below, server side program's codes. Its getting the messages from client with no problem. I want to count this messages length and sending again to client. But it doesnt work. Where am I mistaken?

public NetworkStream str;
        public StreamReader str_rdr;
        public StreamWriter str_wrt;
        public Socket clientsoket;

public void Form1_Load(object sender, EventArgs e)
        {
            CheckForIllegalCrossThreadCalls = false;
            Thread thread_listener = new Thread(new ThreadStart(listen));
            thread_listener.Start();
        }

        public void listen()
        {
            TcpListener listener = new TcpListener(30000);

            while (true)
            {
                listener.Start();
                Socket clientsocket = listener.AcceptSocket();


                    NetworkStream str = new NetworkStream(clientsoket);

                    StreamReader str_rdr = new StreamReader(str);
                    string var1 = str_rdr.ReadLine();
                    textBox1.Text = var1; // ----> In here, I am seeing client's message.

                    StreamWriter str_wrt = new StreamWriter(str);
                    str_wrt.WriteLine(textBox1.Text.Length);
                    str_wrt.Flush();
            }
        }

5 Replies

Know the answer? Post it — somebody with the same question will find it here.

Sam Hobbs16y ago
Accepted answer
See: How to: Make Thread-Safe Calls to Windows Forms Controls. The fact that you set CheckForIllegalCrossThreadCalls to false is a big clue. You should not turn off debugging tools such as that just because you don't know how to solve problems that the debugging tool catches. You are accessing the form from the thread directly, which you should not do. Strange things can happen if you do, and that is why something is happening that you don't understand. Based on that article, you can use code such as the following. In your Form class, add the member:
delegate void SetTextCallback(string text);
Then create a method:
private void SetText(string text)
{
if (textBox1.InvokeRequired)
{
SetTextCallback d = new SetTextCallback(SetText);
this.Invoke(d, new object[] { text });
}
else
{
textBox1.Text = text;
}
}
Then instead of:
textBox1.Text = var1;
Do:
SetText(var1);
Also instead of:
str_wrt.WriteLine(textBox1.Text.Length);
Do:
str_wrt.WriteLine(var1.Length);
That works for me! In my version of your code, I re-arranged other things but I don't know if that affected the results. So if you make the above changes and it still does not work, then we can try some more changes.
Sam Hobbs16y ago
Does your program work when you use the changes I provided? If so then please check the box for my reply indicating it helps. If the program is still not working, then please say so.
yokzu16y ago
Thanks for your advice Sam. I'll try this.
yokzu16y ago
I tried Sam but it doesnt work.
Sam Hobbs16y ago
Try calling str_wrt.Close() after str_wrt.Flush().

I think that C# is sloppy; we have to both flush and close, whereas in C++ the destructor would do the equivalent automatically.