WSACancelBlockingCall exception

Question

Ok, I have a strange exception thrown from my code that\'s been bothering me for ages.

System.Net.Sockets.SocketException: A blocking operation was interrupt         


        

Answer 1

This is my example solution to avoid WSAcancelblablabla: Define your thread as global then you can use invoke method like this:

private void closinginvoker(string dummy)
    {
        if (InvokeRequired)
        {
            this.Invoke(new Action<string>(closinginvoker), new object[] { dummy });
            return;
        }
        t_listen.Abort();
        client_flag = true;
        c_idle.Close();
        listener1.Stop();
    }

After you invoke it, close the thread first then the forever loop flag so it block further waiting (if you have it), then close tcpclient then stop the listener.

Answer 2

Is it possible that the serverSocket is being closed from another thread? That will cause this exception.

Answer 3

Same here! But i figured out, that the ReceiveBuffer on 'server-side' was flooded from the clients! (In my case a bunch of RFID-Scanners, who kept spamming the TagCode, instead of stop sending until next TagCode arrives)

It helped to raise the ReceiveBuffers and reconfigure the scanners...

Answer 4

More recently I saw this exception when using HttpWebRequest to PUT a large file and the Timeout period was passed.

Using the following code as long as your upload time > 3 seconds it will cause this error as far as I could see.

string path = "Reasonably large file.dat";
int bufferSize = 1024;
byte[] buffer = new byte[bufferSize];
System.Net.HttpWebRequest req = (HttpWebRequest)System.Net.HttpWebRequest.Create("Some URL");
req.Method = "PUT";
req.Timeout = 3000; //3 seconds, small timeout to demonstrate
long length = new System.IO.FileInfo(path).Length;
using (FileStream input = File.OpenRead(path))
{
    using (Stream output = req.GetRequestStream())
    {
        long remaining = length;
        int bytesRead = 0;
        while ((bytesRead = input.Read(buffer, 0, (int)Math.Min(remaining, (decimal)bufferSize))) > 0)
        {
            output.Write(buffer, 0, bytesRead);
            remaining -= bytesRead;
        }
        output.Close();
    }
input.Close();
}

Answer 5

This could happen on a serverSocket.Stop(). Which I called whenever Dispose was called.

Here is how my exception handling for the listen thread looked like:

try
{
    //...
}
catch (SocketException socketEx)
{    
    if (_disposed)
        ar.SetAsCompleted(null, false); //exception because listener stopped (disposed), ignore exception
    else
        ar.SetAsCompleted(socketEx, false);
}

Now what happened was, every so often the exception would occur before _disposed was set to true. So the solution for me was to make everything thread safe.