TCP Client/Server Whiteboard - Like Netmeeting - Need advice

I won't get into details of the full project, but one part of the project is a whiteboard-like VI that works similar to the whiteboard in Netmeeting. I created a quick server and client VI to establish a TCP connection to allow the whiteboard to run for everyone. Run the server VI first and then the client VI and the whiteboards will open. Normally you would only have one whiteboard running, but this is a demo to allow the client and server to run on the same computer. Please execute the project to understand what the program does so that you understand the concept.
Now for my problem: I spent a several days designing this portion of my project and it is fairly usable, but the problem is that if you continuously draw on the screen for a long time (maybe 1 minute), the arrays will get rather large and will eventually slow the drawing process to a crawl. In a previous version I would draw to the screen, feedback the picture element, and then clear the array, thinking this would be the most efficient. Unfortunately it seemed to be pretty slow also.
I've only been using Labview for a year, so please forgive me if my code is sloppy or if I did things in a weird way. This is why I am posting this code. I'm really looking for advice on optimizing the code and fixing my main problem.
Attachments:
Whiteboard.zip ‏413 KB

Hi Travis,
Thanks for your reply. I saw your post after I already solved the problem otherwise I would look into your suggestions. I thought I would post the solution here so that this code might help someone in the future.
To recap, I had a problem with a drawing slowdown using two different methods. The first method was to draw to a picture element and then loop this around the main while loop and then draw to the picture element again for every pixel movement captured. Reloading the picture element rapidly was a major drag on the CPU. So the second method I used was to store all pixels movements captured in an array and add another array to the second dimension every time the mouse button lifted. I would draw EVERYTHING in this 2D array everytime I looped around. This meant that the array could get rather large after a very short time and bog down the CPU.
So I realized that I could take the best of both methods mentioned and use a nested while loop inside another while loop. The outer while loop shifts the picture element around and the inner loop will continue to build and redraw only one row of the array until the mouse button is up. At this point I stop the inner loop and pass the picture element around null the arrays for the inner loop. Seems to accomplish everything I needed.
Hope this can help somebody else. The new code is attached
Attachments:
Whiteboard.zip ‏515 KB

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can u explain it http://www.catb.org/~esr/faqs/smart-questions.html#writewell
How To Ask Questions The Smart Way
Eric Steven Raymond
Rick Moen
Write in clear, grammatical, correctly-spelled language
We've found by experience that people who are careless and sloppy writers are usually also careless and sloppy at thinking and coding (often enough to bet on, anyway). Answering questions for careless and sloppy thinkers is not rewarding; we'd rather spend our time elsewhere.
So expressing your question clearly and well is important. If you can't be bothered to do that, we can't be bothered to pay attention. Spend the extra effort to polish your language. It doesn't have to be stiff or formal - in fact, hacker culture values informal, slangy and humorous language used with precision. But it has to be precise; there has to be some indication that you're thinking and paying attention.
Spell, punctuate, and capitalize correctly. Don't confuse "its" with "it's", "loose" with "lose", or "discrete" with "discreet". Don't TYPE IN ALL CAPS; this is read as shouting and considered rude. (All-smalls is only slightly less annoying, as it's difficult to read. Alan Cox can get away with it, but you can't.)
More generally, if you write like a semi-literate b o o b you will very likely be ignored. So don't use instant-messaging shortcuts. Spelling "you" as "u" makes you look like a semi-literate b o o b to save two entire keystrokes.

Help with MIDlets - TCP client server program

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Code:
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All,
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Micks80 wrote:
Hi Friends,
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Hello all,
1. We are new in network programming, so please
forgive us for such a dum question.
In our last project we were requested to write a very
simple java server which would handle some "Task
process" state by recieving commands
"start,stop,getStatus".
Although we were able to easily write the code, we
had a doubt that created a team discussion.
Were should the socket connection be stablished ?
Some of us stated that the "Constructor" should
establish the connection to the socket, as the
"Server" can not exists if it is not listening to a
port.
Some others stated that a "Run/Start" method should
do this.
Obviouly either way works, yet I'm hopping that the
Gurus here can help us determine the right answer.
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2. I read about MVC pattern but I can't find a link
to a well explained "Client-Server" pattern. Does
anyone know a good place to find patterns ?
Thanks in advanced for you help !!!
It's great to be part of this community.
Thanks..Do a Google search on writing a multi-threaded server. A number of patterns could apply. Client-server is really an architecture, not a pattern. Any number of patterns (or anti-patterns) could actually implement it.
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We are trying to better understand customer views on social support experience, so your participation in this interview project would be greatly appreciated if you have time. Thanks for helping make community forums a great place.
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greeting
Thomas

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*lost*
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Go to Solution.

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Attachments:
TCP Comm.zip ‏47 KB

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private TcpListener tcpListener;
private bool isStarted;
public event Action<string> NewMessage;
public async Task Start(int port)
this.tcpListener = TcpListener.Create(port);
this.tcpListener.Start();
this.isStarted = true;
while (this.isStarted)
var tcpClient = await this.tcpListener.AcceptTcpClientAsync();
var cts = new CancellationTokenSource();
this.cancellationTokens.Add(cts);
await Task.Factory.StartNew(() => this.Process(cts.Token, tcpClient), cts.Token, TaskCreationOptions.LongRunning, TaskScheduler.Default);
public void Stop()
this.isStarted = false;
foreach (var cancellationTokenSource in this.cancellationTokens)
cancellationTokenSource.Cancel();
foreach (var tcpClient in this.clients.Values)
tcpClient.GetStream().Close();
tcpClient.Close();
this.clients.Clear();
public async Task SendMessage(string message, IPEndPoint endPoint)
try
var tcpClient = this.clients[endPoint];
await this.Send(tcpClient.GetStream(), Encoding.ASCII.GetBytes(message));
catch (Exception exception)
private async Task Process(CancellationToken cancellationToken, TcpClient tcpClient)
try
var stream = tcpClient.GetStream();
this.clients.Add((IPEndPoint)tcpClient.Client.RemoteEndPoint, tcpClient);
while (!cancellationToken.IsCancellationRequested)
var data = await this.Receive(stream);
this.NewMessage.SafeInvoke(Encoding.ASCII.GetString(data));
catch (Exception exception)
private async Task Send(NetworkStream stream, byte[] buf)
await stream.WriteAsync(BitConverter.GetBytes(buf.Length), 0, 4);
await stream.WriteAsync(buf, 0, buf.Length);
private async Task<byte[]> Receive(NetworkStream stream)
var lengthBytes = new byte[4];
await stream.ReadAsync(lengthBytes, 0, 4);
var length = BitConverter.ToInt32(lengthBytes, 0);
var buf = new byte[length];
await stream.ReadAsync(buf, 0, buf.Length);
return buf;
Client
public class Client
private TcpClient tcpClient;
private NetworkStream stream;
public event Action<string> NewMessage;
public async void Connect(string host, int port)
try
this.tcpClient = new TcpClient();
await this.tcpClient.ConnectAsync(host, port);
this.stream = this.tcpClient.GetStream();
this.Process();
catch (Exception exception)
public void Disconnect()
try
this.stream.Close();
this.tcpClient.Close();
catch (Exception exception)
public async void SendMessage(string message)
try
await this.Send(Encoding.ASCII.GetBytes(message));
catch (Exception exception)
private async void Process()
try
while (true)
var data = await this.Receive();
this.NewMessage.SafeInvoke(Encoding.ASCII.GetString(data));
catch (Exception exception)
private async Task Send(byte[] buf)
await this.stream.WriteAsync(BitConverter.GetBytes(buf.Length), 0, 4);
await this.stream.WriteAsync(buf, 0, buf.Length);
private async Task<byte[]> Receive()
var lengthBytes = new byte[4];
await this.stream.ReadAsync(lengthBytes, 0, 4);
var length = BitConverter.ToInt32(lengthBytes, 0);
var buf = new byte[length];
await this.stream.ReadAsync(buf, 0, buf.Length);
return buf;

Hi,
Have you debug these two applications? Does it go into the catch exception block when you close the client or the server?
According to my test, it will throw an exception when the client or the server is closed, just log the exception message in the catch block and then you'll get it:
private async void Process()
try
while (true)
var data = await this.Receive();
this.NewMessage.Invoke(Encoding.ASCII.GetString(data));
catch (Exception exception)
Console.WriteLine(exception.Message);
Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host.
By the way, I don't know what the SafeInvoke method is, it may be an extension method, right? I used Invoke instead to test it.
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Need help in desigining Client/Server Application using Java

Hi,
I am new to Java and no sooner that I started studing it I have been given a project - client server java Application that allows a user to do a property search based on critiras (eg location, price) and display the results. I am stuck because I don't know where I need to start. Have to use IDE (Netbeans or Eclipse) but not sure about dev frameworks.
Can someone give me an outline of what I should do / where I should start? What will be the best solution?
Thanks in adance

http://java.sun.com/docs/books/tutorial/networking/index.html
That's Sun's networking tutorial series. Live it, learn it, love it. You'll need to decide if you want to use connected sockets or datagrams. You'll need details like, can multiple clients connect simultaneously?
The tutorials are the first step though.

TCP Client/Server Whiteboard - Like Netmeeting - Need advice

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