CODEWITHSUNDEEP
c#asynchronousnetwork-programmingwindows-phone-7.1windows-phone
Switchice
Switchice

Reputation: 63

How to (really) cancel a ConnectAsync request on Windows Phone?

I'm developing a Windows Phone application that will connect to my server. It does this by using ConnectAsync when you push the login button. But if the server is down and you want to cancel the connecting attempt, what to do?

Here is is the current client code complete with my latest try at shutting the socket connection down. It is to be assumed that you can easily implement a timeout once you know how to turn the connection off.

    private IPAddress ServerAddress = new IPAddress(0xff00ff00); //Censored my IP
    private int ServerPort = 13000;
    private Socket CurrentSocket;
    private SocketAsyncEventArgs CurrentSocketEventArgs;
    private bool Connecting = false;

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        try
        {
            if (Connecting)
            {
                CurrentSocket.Close();
                CurrentSocket.Dispose();
                CurrentSocketEventArgs.Dispose();
                CurrentSocket = null;
                CurrentSocketEventArgs = null;
            }
            UserData userdata = new UserData();
            userdata.Username = usernameBox.Text;
            userdata.Password = passwordBox.Password;

            Connecting = ConnectToServer(userdata);
        }
        catch (Exception exception)
        {
            Dispatcher.BeginInvoke(() => MessageBox.Show("Error: " + exception.Message));
        }
    }

    private bool ConnectToServer(UserData userdata)
    {
        CurrentSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

        //Create a new SocketAsyncEventArgs
        CurrentSocketEventArgs = new SocketAsyncEventArgs();
        CurrentSocketEventArgs.RemoteEndPoint = new IPEndPoint(ServerAddress, ServerPort);
        CurrentSocketEventArgs.Completed += ConnectionCompleted;
        CurrentSocketEventArgs.UserToken = userdata;
        CurrentSocketEventArgs.SetBuffer(new byte[1024], 0, 1024);

        CurrentSocket.ConnectAsync(CurrentSocketEventArgs);
        return true;
    }

Edit: A thought that struck me is that perhaps it's the server computer that stacks up on requests even though the server software isn't on? Is that possible?

Upvotes: 5

Views: 2173

Answers (3)

fishingpole
fishingpole

Reputation: 43

What's going on here is that you are specifying a buffer in the argument to ConnectAsync.

CurrentSocketEventArgs.SetBuffer(new byte[1024], 0, 1024);

The documentation says:

Optionally, a buffer may be provided which will atomically be sent on the socket after the ConnectAsync method succeeds.

So your server is going to see the connection and data at once. Your cancellation code is just fine, it's just that the data is sent before you get a chance to cancel anything.

Upvotes: 0

Soonts
Soonts

Reputation: 21936

Your code looks OK. As already said by Marc, closing the socket cancels all pending operations.

Yes, it's sometimes possible that you connect OK and nothing happens. To verify, in the command line

telnet 192.168.1.44 31337 where 192.168.1.44 is ServerAddress (name is OK as well) and 31337 is ServerPort. You might first enable a "Telnet client" using Control Panel/Programs and Features/Turn Windows features on and off. If you see "Could not open connection" = your WinForms application shouldn't be able to connect. If you see a black screen with blinking cursor = your WinForms application should connect OK.

Upvotes: 0

MarcF
MarcF

Reputation: 3299

I believe

socket.Close()

should cancel the async connection attempt. There may be some exceptions that need to be caught as a consequence.

Upvotes: 3

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