Asynchronous Sockets ERROR

or nakash

I am getting an error in this code:

        public void OnDataReceived(IAsyncResult asyn)
        {
            try
            {
                CSocketPacket theSockId = (CSocketPacket)asyn.AsyncState;
                //end receive...
                int iRx = 0;
                iRx = theSockId.thisSocket.EndReceive(asyn);
                char[] chars = new char[iRx + 1];
                System.Text.Decoder d = System.Text.Encoding.UTF8.GetDecoder();
                int charLen = d.GetChars(theSockId.dataBuffer, 0, iRx, chars, 0);
                System.String szData = new System.String(chars);
                richTextBox1.Text += szData;
                WaitForData(m_socWorker);
            }
            catch (ObjectDisposedException)
            {
                System.Diagnostics.Debugger.Log(0, "1", "\nOnDataReceived: Socket has been closed\n");
            }
            catch (SocketException se)
            {
                MessageBox.Show(se.Message);
            }
        }

THE UNDERLINE CODE GIVES ME THIS ERROR:

Cross-thread operation not valid: Control 'richTextBox1' accessed from a thread other than the thread it was created on.

And one more question, how to do that when I type the string "pw1313" it executes a Console.Beep(); event?

6 Replies

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

Sam Hobbs16y ago
Accepted answer
That's easy. Look at How to: Make Thread-Safe Calls to Windows Forms Controls. Your OnDataReceived function executes asynchronously; in other words, in a separate thread. So you can't directly access the richTextBox1 control from the OnDataReceived function because controls are not thread-safe.

The SetText function in the article is a little confusing. What happens is that the InvokeRequired method determines if the function is being called from a thread different from the thred that the control is in. If the threads are different, then the function gets called again but from within the thread that the control is in.
or nakash16y ago
I tried to do this under ReceiveData :

        private void ReceiveData()
        {
            try
            {
                byte[] buffer = new byte[1024];
                int iRx = m_socClient.Receive(buffer);
                char[] chars = new char[iRx];

                System.Text.Decoder d = System.Text.Encoding.UTF8.GetDecoder();
                int charLen = d.GetChars(buffer, 0, iRx, chars, 0);
                System.String szData = new System.String(chars);
                if(szData == "kuku")
                {
                       Console.Beep();
                }

                string Time = "[" + DateTime.Now.Hour + ":" + DateTime.Now.Minute + ":" + DateTime.Now.Second + "]";
                AppendText(Time+szData+"\n");
            }
            catch (SocketException se)
            {
                //MessageBox.Show(se.Message);
            }
        }

And it didn't work,maybe I did something wrong?
I can't find a good OnDataReceived,but I tried the OnDataRecieved on the server program and it didn't work either.
Sam Hobbs16y ago
Calling Console.Beep when "kuku" is received is so easy to do that perhaps I don't understand the question.
or nakash16y ago
Thank you very much,it works perfectly ;)
I just changed SetText to AppendText,you forgot to change it ;p

One more question, how do I do actions between the client and server?
I want when the client gets the string "kuku" it will make a Console.Beep event.

Sam Hobbs16y ago

private void AppendText(string text)

        {

            // InvokeRequired required compares the thread ID of the

            // calling thread to the thread ID of the creating thread.

            // If these threads are different, it returns true.

            if (this.richTextBox1.InvokeRequired)

            {    

                SetTextCallback d = new SetTextCallback(SetText);

                this.Invoke(d, new object[] { text });

            }

            else

            {

                richTextBox1.Text += text;

            }

        }

Be sure to also use:

delegate void SetTextCallback(string text);

As shown in the MSDN sample. Then call AppendText(szData) instead of:

richTextBox1.Text += szData;

or nakash16y ago
I tried to do that but I faild.
Can you show me how to combine this with my code?