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I tried to make a little UWP card game to learn how to use TCP, but my server always stops responding to the client after a few connections.

The client sends different messages to the server, like "DrawCard;(name of card)". Interestingly, the first 30-40 messages always reach the server without a problem, but after certain types of messages the server just stops accepting any new ones: For instance, I can draw as many cards as I like, but when I play one, the server stops listening.

I have tried to solve this problem for a few hours now, so I hope someone can help me.

When the app starts, this function is called:

public async static Task StartListening()
    {
        Windows.Networking.Sockets.StreamSocketListener socketListener = new Windows.Networking.Sockets.StreamSocketListener();
            socketListener.ConnectionReceived += SocketListener_ConnectionReceived;

            await socketListener.BindServiceNameAsync("1337");

            //If I leave this line out, it doesn´t even start listening for connections. Any idea why?
            await System.Threading.Tasks.Task.Delay(500);
}

This is the event that gets triggered when a connection is received:

public async static void SocketListener_ConnectionReceived(Windows.Networking.Sockets.StreamSocketListener sender,
Windows.Networking.Sockets.StreamSocketListenerConnectionReceivedEventArgs args)
    {
            Stream inStream = args.Socket.InputStream.AsStreamForRead();
            StreamReader reader = new StreamReader(inStream);
            string request = await reader.ReadLineAsync();

            HandleData(request);

            ////Send the line back to the remote client.
            Stream outStream = args.Socket.OutputStream.AsStreamForWrite();
            StreamWriter writer = new StreamWriter(outStream);
            await writer.WriteLineAsync(request);
    }

HandleData() uses 

await CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(CoreDispatcherPriority.Normal,
                    () =>
                    {
                         /...
                    });

to edit some ObservableCollections that are bound to UI elements.

The client code is:

public async Task SendDataToServer(string data)
    {
        Windows.Networking.Sockets.StreamSocket socket = new Windows.Networking.Sockets.StreamSocket();

            Windows.Networking.HostName serverHost = new Windows.Networking.HostName(hostname);

            string serverPort = "1337";
            await socket.ConnectAsync(serverHost, serverPort);

            //Write data to the server.
            Stream streamOut = socket.OutputStream.AsStreamForWrite();
            StreamWriter writer = new StreamWriter(streamOut);
            await writer.WriteLineAsync(data);

            //Read data from the server.
            Stream streamIn = socket.InputStream.AsStreamForRead();
            StreamReader reader = new StreamReader(streamIn);
            string response = await reader.ReadLineAsync();
        }
    }

In my test scenario, the client app runs on my Windows Mobile phone and the server runs on my PC. The PC doesn´t send any data back to the client apart from returning the received message to make sure it was received correctly.

Thank you very much for any help you can offer. I have tried everything I could find on the Internet, but I didn´t find anything that worked for me.

LinusWP
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  • using wireshark, can you see your client app sending packets when the server stops responding? also, in your code, you should always dispose of socket, Streams, DataWriters, DataReaders, StreamWriters, objects when you are done with them. let me know how you go after you try that. – MrCSharp Apr 03 '17 at 05:24
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    For StreamSocket, you can refer to the official [StreamSocket sample](https://github.com/Microsoft/Windows-universal-samples/tree/master/Samples/StreamSocket) and also [Sockets](https://learn.microsoft.com/en-us/windows/uwp/networking/sockets). If you still have problem, please share a [mcve] that can reproduce your issue. – Jay Zuo Apr 03 '17 at 08:09
  • @Rafeal Thank you very much for your reply. Unfortunately, Disposing doesn't change the behaviour. The client does send its data, the server doesn't respond. – LinusWP Apr 03 '17 at 17:17
  • @Jay Zuo Thank you very much for the links. I'm going to look at them tomorrow. – LinusWP Apr 03 '17 at 17:19
  • @JayZuo-MSFT - I found the solution in the StreamSocket sample. I added it as an answer. Thanks both of you! – LinusWP Apr 04 '17 at 18:21

1 Answers1

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Thank you very much @Jay Zuo - MSFT! I looked at the official samples and found out that I missed the following line of code:

CoreApplication.Properties.Add("listener", socketListener);

According to the MS sample, this "save[s] the socket, so subsequent steps can use it." The app works as intended now. Thank you very much for your help, @Rafael and @Jay Zuo - MSFT !

LinusWP
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