WPF async await TcpClient/TcpListener sample

Question

I want to build a robust and highly scalable client server system. Here what I have so far(an echo server as my base of implementation)

My Server

 private void startServer_Click(object sender, RoutedEventArgs e)
 {
 if (anyIP.IsChecked == true)
 {
 listener = new TcpListener(IPAddress.Any, Int32.Parse(serverPort.Text));
 Logger.Info("Ip Address : " + IPAddress.Any + " Port : " + serverPort.Text);
 }
 else
 {
 listener = new TcpListener(IPAddress.Parse(serverIP.Text), Int32.Parse(serverPort.Text));
 Logger.Info("Ip Address : " + serverIP.Text + " Port : " + serverPort.Text);
 }
 try
 {
 listener.Start();
 Logger.Info("Listening");
 HandleConnectionAsync(listener, cts.Token);
 }
 //finally
 //{
 //cts.Cancel();
 //listener.Stop();
 //Logger.Info("Stop listening");
 //}
 //cts.Cancel();
 }
 async Task HandleConnectionAsync(TcpListener listener, CancellationToken ct)
 {
 while (!ct.IsCancellationRequested)
 {
 Logger.Info("Accepting client");
 //TcpClient client = await listener.AcceptTcpClientAsync();
 TcpClient client = await listener.AcceptTcpClientAsync();
 Logger.Info("Client accepted");
 EchoAsync(client, ct);
 }
 }
 async Task EchoAsync(TcpClient client, CancellationToken ct)
 {
 var buf = new byte[4096];
 var stream = client.GetStream();
 while (!ct.IsCancellationRequested)
 {
 var amountRead = await stream.ReadAsync(buf, 0, buf.Length, ct);
 Logger.Info("Receive " + stream.ToString());
 if (amountRead == 0) break; //end of stream.
 await stream.WriteAsync(buf, 0, amountRead, ct);
 Logger.Info("Echo to client");
 }
 }
 private void stopServer_Click(object sender, RoutedEventArgs e)
 {
 cts.Cancel();
 listener.Stop();
 Logger.Info("Stop listening");
 }

My Client

 private void connect_Click(object sender, System.Windows.RoutedEventArgs e)
 {
 IPAddress ipAddress;
 int port;
 //TODO Check if ip address is valid
 ipAddress = IPAddress.Parse(serverIP.Text);
 //TODO port range is 0-65000
 port = int.Parse(serverPort.Text);
 StartClient(ipAddress, port);
 }
 private static async void StartClient(IPAddress serverIpAddress, int port)
 {
 var client = new TcpClient();
 //can i try/catch to catch await exception?
 try
 {
 await client.ConnectAsync(serverIpAddress, port);
 }
 catch (Exception e)
 {
 Logger.Info(e); 
 }
 Logger.Info("Connected to server");
 using (var networkStream = client.GetStream())
 using (var writer = new StreamWriter(networkStream))
 using (var reader = new StreamReader(networkStream))
 {
 writer.AutoFlush = true;
 for (int i = 0; i < 10; i++)
 {
 Logger.Info("Writing to server");
 await writer.WriteLineAsync(DateTime.Now.ToLongDateString());
 Logger.Info("Reading from server");
 var dataFromServer = await reader.ReadLineAsync();
 if (!string.IsNullOrEmpty(dataFromServer))
 {
 Logger.Info(dataFromServer);
 }
 }
 }
 if (client != null)
 {
 client.Close();
 Logger.Info("Connection closed");
 }
 }

Answer 1

1. The general issue with your code is that your client and server implementations reside in your control's code-behind. It is always a good idea to separate business logic from UI.

2. This is copy-paste:

   if (anyIP.IsChecked == true)
   {
    listener = new TcpListener(IPAddress.Any, Int32.Parse(serverPort.Text));
    Logger.Info("Ip Address : " + IPAddress.Any + " Port : " + serverPort.Text);
   }
   else
   {
    listener = new TcpListener(IPAddress.Parse(serverIP.Text), Int32.Parse(serverPort.Text));
    Logger.Info("Ip Address : " + serverIP.Text + " Port : " + serverPort.Text);
   }
   

   can be refactored to:

   var ip = anyIP.IsChecked == true ? IPAddress.Any : IPAddress.Parse(serverIP.Text);
   var port = Int32.Parse(serverPort.Text);
   listener = new TcpListener(ip, port);
   Logger.Info(String.Format("Ip Address : {0} Port : {1}", ip, port));
   

3. Its a good style to prefix fields with underscore, so they can be distinguished from local variables. So it should be _listener instead of listener.

4. You should shut down your server on exit.

5. Yes, as long, as you await the call you can catch exceptions.

• Syaiful Nizam Yahya: Thank you. 1 and 2. I write it as fast as i can and i know its ugly. 3. I didnt know that. Thanks. 4. Youre right. 5. Thank you for that confirmation.