Posts by ktsangop

Sorry about the late answer but i had to open the device eventually.
One of the drives was failing now and then, and had to be replaced.

Looks like the default configuration was raid 0 (lame).
Lucky for them i managed to get a full backup of both drives, replaced the faulty one and created a new configuration (raid 1 this time).

Anyway @mechbas, maybe it wasn't clear enough but there is no way to look at the device's bios (if there is such thing in a NAS).
This is the device
http://support.wdc.com/product/install.asp?groupid=107
And you can only access it by a web interface or ssh.

Hello everyone.
I would like to know if there is a factory default configuration for the WD My book world NAS.
I am helping a friend that has one of those in their office and the web interface states that the capacity is 1TB but nowhere in the gui did i find anything about the current raid configuration.

The only option is to change it.
I would like to know if it has 2x1TB disks running raid 1 or 2x500GB disks running raid 0. Nothing found on Western Digital's website or manuals.

Thanks in advance!

UPDATE:

After creating two new server machines, and keeping one that was getting a lot of timeouts, i have the following results :

For 100 thread runs over 20 minutes :

NEW_SERVER1 : 99 successful connections/ 1 timeouts
NEW_SERVER2 : 94 successful connections/ 6 timeouts
OLD_SERVER  : 57 successful connections/ 43 timeouts

Other info :
- I experienced a JRE crash (EXCEPTION_ACCESS_VIOLATION (0xc0000005)) once and had to restart the application.
- I noticed that while the app was running my network connection was struggling as i was browsing the internet. I have no idea if this is expected but i think my having at MAX 15 threads is not that much.

So, fisrt of all my old servers had some kind of problem. No idea what that was, since my new servers were created from the same OS image.

Secondly, although the timeout percentage has dropped dramatically, i still think it is uncommon to get even one timeout in a small LAN like ours. But this could be a server's application part problem.

Finally my point of view is that, apart from the old server's problem (i still cannot beleive i lost so much time with that!), there must be either a server app bug, or a JDK related bug (since i experienced that JRE crash).

p.s. I use Eclipse as IDE and my JRE is the latest.

If any of the above ring any bells to you, please comment.
Thank you.

Thank you ~s.o.s~ for your effort.
I tried almost everything the past 3 days and i too cannot figure something out. I will try to setup another dummy server, to test this.
Seems impossible for an application that has been running since 2010, to show such a strange behaviour, but everything else has been ruled out. It might be the server...
:-(

The server is in C and it uses INADDR_ANY as local address which i always thought was 127.0.0.1 right?
Could this be problematic?

The servers are all identical.

Using SocketSniff i tried to monitor my remote server to see if the packets are arriving there correctly.

What i got was something like this:
(My java app runs on 192.168.1.7, the remote server on 192.168.1.159)
A normal send/receive call (data are not shown here but are correct):

==================================================
Socket            : 0x000006A0
Index             : 3
Type              : TCP
Local Address     : 192.168.1.159
Local Port        : 2223
Remote Address    : 192.168.1.7
Remote Port       : 6376
Send Calls        : 1
Receive Calls     : 1
Sent              : 22
Received          : 12
Closed            : Yes
==================================================

A call which timed out (no data exist here) :

==================================================
Socket            : 0x000006E0
Index             : 5
Type              : TCP
Local Address     : 0.0.0.0
Local Port        : 2223
Remote Address    : 192.168.1.7
Remote Port       : 6403
Send Calls        : 0
Receive Calls     : 1
Sent              : 0
Received          : 0
Closed            : Yes
==================================================

So the obvious difference, is that the local address is presented as 0.0.0.0 . Is this normal?

Could anybody see anything abnormal that i can't?

Thanks.

Just wanted to inform you that an advertisment i clicked on, leads to a non working link. Seems that the forwarded link
is missing the semicolon (:) after http.
I click on ads once a year maybe so i had to report it...
:D
This is the url behind the ad image (i am using chrome):

http://ad.doubleclick.net/click;h=v8/3e52/c/368/%2a/j;275635761;1-0;0;84203148;4307-300/250;55680243/55569532/1;;~okv=;pc=[TPAS_ID];;~sscs=%3fhttp://adclick.g.doubleclick.net/aclk?sa=l&ai=CgVqoJp0lUurcNfOhiga9n4HACKDO6JsC2LOd1R_UoYyMEhABIABQgMfhxARgrQKCARdjYS1wdWItODQyNjY0MTYzNzEyMzk0NaABrKq78gPIAQngAgCoAwGqBOcBT9CO1ZIg79FSQ10xq2BN15a4OK5MtqkQh7UcgpOpQKF2cOWg1mUj5fuL85_3QY01rkcS8tObm81DD5YzLuelyY5DVqy47RERl31x_BptHoCnVHW8qyYt9wjCMB9q4HhA1GuqdiWWgtztZvyTCnVCEzdbI9A1i38jeEpQ9_n0JjEj-lFEaZSdXRTU2pnl35PMt-MTIMrCQGEwPGLUPSS31M8CekAmu91xJNE5kxnP-0P4zspZgGTXp3XMA8X1jW2_YdBih2NB8GlIf8_CVdMQ5yu3xFvJgv8Oa4SRK6O4z5NBG4KX5Xe24AQBgAab4Zb6-eCm5-IBoAYh&num=1&sig=AOD64_17YCz44trAmF2UHR0NY2S3S0uq1w&client=ca-pub-8426641637123945&adurl=http%3A%2F%2Fbub.px.invitemedia.com%2Fpixel%3FreturnType%3Dredirect%26key%3DClick%26b%3Doho294.ovq.wiz.cebq2%26message%3DeJwNzLEKg0AQBNB_mXqL7Ll7XrYzpEpAtBD7EAgSPW2MEPHf3WKKeTCzg2Hohv79.FT1a5qf23L_D9Wt.bUgKKy46JVQwkJKzIQAE0KERZFQEgoH1iQeL3625m.et.xrgeV1HJ3dg2rk4wRQGBu.%26redirectURL%3Dhttp%3a%2f%2fhttp%3A//www.threadless.com/%3Futm_medium%3Dbanner%26utm_source%3Daod%26utm_campaign%3DLD15_Intl

Hope that helped some way!
:)

You mean you get a TimeOutException before 10 secs on some live PCs?

No, i get a normal timeout after 10 seconds, even though the remote socket is accepting connections.

What happens if the list contains one non-working PC?

Well i'll have to look at it and post back.
EDIT: Just a normal timeout after 10 seconds with a typical timoutexception.

The servers are written by me, but have been working for more than 2 years, without any problem. I'm trying to add extra functionality to my client with those extra threads.

Also, I believe your code needs a bit more logging

I've removed them from my post (to keep it cleaner) but they exist on my source file.

Thanks, i will post back some more results soon enough.

Hello!
I would like some help with a piece of java code that i'm having problem.

I have to make simultaneous tcp socket connections every x seconds to multiple machines, in order to get something like a status update packet.

I use a Callable thread class, which creates a future task that connects to each machine, sends a query packet, and receives a reply which is returned to the main thread that creates all the callable objects.

My socket connection class is :

public class ClientConnect implements Callable<String> 
{
    Connection con = null;
    Statement st = null;
    ResultSet rs = null;
    String hostipp, hostnamee; 
    ClientConnect(String hostname, String hostip)
    {
        hostnamee=hostname;
        hostipp = hostip;
    }
    @Override
    public String call() throws Exception 
    {
        return GetData();
    }
    private String GetData()
    {
            Socket so = new Socket();
            SocketAddress sa =  null;
            PrintWriter out = null;
            BufferedReader in = null;
        try 
        {
            sa = new InetSocketAddress(InetAddress.getByName(hostipp), 2223);
        } 
        catch (UnknownHostException e1) 
        {
            e1.printStackTrace();
        }
        try 
        {
            so.connect(sa, 10000);

            out = new PrintWriter(so.getOutputStream(), true);
            out.println("\1IDC_UPDATE\1");
            in = new BufferedReader(new InputStreamReader(so.getInputStream()));
            String [] response = in.readLine().split("\1");             
            out.close();in.close();so.close(); so = null;

            try{
                Integer.parseInt(response[2]);
            }
            catch(NumberFormatException e)
            {
                System.out.println("Number format exception");
                return hostnamee + "|-1" ;
            }

            return hostnamee + "|" + response[2];

        } 
        catch (IOException e) 
        {
            try {
                if(out!=null)out.close();
                if(in!=null)in.close();
                so.close();so = null;
                return hostnamee + "|-1" ;
            } catch (IOException e1) {
                // TODO Auto-generated catch block
                return hostnamee + "|-1" ;
            }

        }

        }
}

And this is the way i create …

Thanks, i will try to insert some dummy data and test it.
It's just that i've always wondered why we are able to leave a table key-less anyway...

That's working just fine!

This is probably another thread's question but would there be a problem in large data sets, considering that there is no primary key, and the "ELSE" condition could contain a lot of un-indexed rows?

Thank you!

Hello everyone!
Is it possible to write a query which does the following :

UPDATE db.table 
SET col1 = 1 
WHERE col2='something' AND col3 IN ('a','b','c')
ELSE SET col1 = 0

Meaning that the rows that don't match the where conditions will also be updated to another value.
Note that db.table has no primary key, but foreign key only.
:S

edit : I am looking for a single query of course!

Thanks in advance!

Nice to know. I should read about iterator invalidation rules i suppose... my STL knowledge needs to be refreshed as it seems like i forgot everything...
:D

Thank you Gonbe!

Awww! Why didn't i think of that???!!
:)
Thanks a lot that seems to work!

By the way is there any reason that someone should use an iterator for this? Would it be more secure or fast?

Thanks again!

Hello everyone!
I would like your help regarding this:
I have a tuple vector which i must iterate through, and accessing the vector data to decide wether to erase or not the current vector element.
My code :

typedef tuple <int, CString, int, int> pc_data;
vector <pc_data> pc_vec;

//Assume that pc_vec is filled with elements somewhere here...


//This code is not working. 
//Exception : vector subject out of range because of the size dynamically changing i suppose
for (int i=0; i<num_of_pcs; i++)
{
    if(std::get<2>(pc_vec[i])==0)
        pc_vec.erase(pc_vec.begin()+i);
}

//second try
//No exception here but the dynamic size of the vector again won't let me access all elements sequentially
for (size_t i = 0; i < pc_vec.size(); i++)
{
    if(std::get<2>(pc_vec[i])==0)
        pc_vec.erase(pc_vec.begin()+i);
}

//third try
//use iterator
vector<pc_data>::iterator it = pc_vec.begin();
//I don't know how to access the current element data in this situation..(?)
for ( ; it != pc_vec.end(); ) 
{
    if(std::get<2>(/*WHAT SHOULD I USE TO ACCESS THE CURRENT ELEMENT HERE??*/)==0)
    {
        it = pc_vec.erase(it);
    } 
    else 
    {
        ++it;
    }
}

Could you please suggest me a way to do it?
Thanks in advance and hope my question is clear enough.

Sorry i didn't post any code, i was in a hurry and wanted a suggestion because i was stuck.
In the end, i worked it over last night and managed to do it.

The key was to use setTimeout function with a variable timeout parameter. Timeout should be calculated on each call, using the previous and current value, and then passed to the next setTimeout call.

Thanks anyway.

Hi everyone.

I would like to implement a counter using ajax that will act like this:
The script will send a XMLHttpRequest every x seconds which will return a value from a mysql database.
Using the current and previous value retrieved from the server, the script will increase the counter, in order to reach the new value in the x second interval between the server requests.

The value will be decimal (two decimal digits are enough), it will always icrease (until it resets) and my main concern is to make it increase with variable speed, to give a more interesting visual effect. Meaning that if the (current value - previous value) is big the counter will speed up to "catch up".

I already have code that reads a value from a database and just prints it to a html div element every x seconds.
So i would like a suggestion on the counter increase algorithm.

Hope i made it clear... :)

Thanks in advance.

Looks like i 've misunderstood the whole idea here.
I had the answer in front of my eyes from the beginning :

ssh -nNT -R :5000:localhost:3389 username@server-ip

I simply changed port 22 to 3389, which is the rdp server port..

I thought that the ssh tunnel was supposed to work between two ssh servers and then i would be able to forward any ports someway. But the truth is that you can directly forward any port since the tunnel is ready.

Cheers!

I've been working with Cygwin for years now, and i may say that it is one of the most robust "applications" i've ever seen. The ssh server of Cygwin is the last service that i would expect to crash, even if all of the operating system is unresponsive.

In addition to that, i don't think that there will be any difference since both of them just implement the ssh server which is quite the same in all the platforms i ever used it.

I found the answer to my first question.
I changed the first code line to :

ssh -nNT -R :5000:localhost:22 username@server-ip

The empty ip before :5000 indicates that a connection can be established from any external ip.

and added this line in my linux server's sshd_config file which enables port 5000 to be a gateway for incoming connections

GatewayPorts yes

And now i am able to connect to the windows pc using the following command from any computer with internet access :

ssh username@server-ip -p 5000

Now the second question remains unanswered. I read a lot of guides and i am pretty confused.
Is there anyway i can forward the rdp port (3389) to the ssh tunnel so i can connect from any pc?

I think it is possible but i can't figure out how to do it.

Hi everyone!
I am trying to set up a reverse ssh tunnel from a windows machine using Cygwin (openssh) , to a Linux server machine with static ip, so i can access the windows pc directly through the server from any other machine.
My ultimate goal is to be able to connect through remote desktop (rdp) to the windows pc from any other pc through the ubuntu server.

I managed to take the first step which is setup a ssh server in cygwin and to open a reverse ssh tunnel from windows pc to the server using the following command in cygwin :

ssh -nNT -R server-ip:5000:localhost:22 username@server-ip

So with tunnel running i can connect from any other pc to the windows pc with the following two steps:
1) connect to the linux server

ssh username@server-ip

2) connect to the windows pc using the tunnel created earlier

ssh username@localhost -p 5000

My first question is this :
Why can't i use directly the following command from any PC to connect directly to the tunnel:

ssh username@server-ip -p 5000
ssh: connect to host server-ip port 5000: Connection refused

Is there anyway to set this up?

Secondly, if i manage to do this, is there a way to forward rdp port so i can connect directly from any pc to the windows client using remote desktop protocol?
Using something like :

ssh -L 3390:localhost:3389 username@server-ip

Thanks in advance.

I did it another way eventually.
I made my own modal jdialog class like the following page suggests :
http://stackoverflow.com/a/4089370

Thanks.

First suggestion worked as expected. The dialog appears in the center of the parent.
For the second i did the following :

    public int confirmationBox(String infoMessage, String location)
    {
        JOptionPane a = new JOptionPane();
        a.setLocation(100,100);

        int response = a.showConfirmDialog(null, infoMessage, "Confirmation : " + location, JOptionPane.INFORMATION_MESSAGE);
        return response;
    }

but it didn't work. Neither with null as parent nor with the actual parent window.

Could you please elaborate on this?

Hello everyone!
Just as the title suggests, i would like to know if it's possible to set the position of a dialog box.
The default behaviour, is to appear in the center of the screen
I use it this way :

    public static int confirmationBox(String infoMessage, String location)
    {
        int response = JOptionPane.showConfirmDialog(null, infoMessage, "Confirmation : " + location, JOptionPane.INFORMATION_MESSAGE);
        return response;
    }

Thanks in advance!

Being familiar with callbacks, it was easier for me to understand it that way!
Java's abstraction is really great, but it takes sometime to get used to it i suppose, specially if you are used to old-school winapi development!

Thanks James, i've read about the BlockingQueue, and it seems like a nice and clean solution for message passing, but it is not event driven and it leaves the implementation of the dispatching to you.

This seems like a more transparent way to implement it :
http://www.javaworld.com/javatips/jw-javatip10.html
Do you have any experience on this subject?
Would you suggest it?

Thanks again.

Thanks for the insight.
I am not trying to apply the exact same model. All i want is a suggestion on which thread communication model is closer to the one i described. I am going to learn java eventually, but i just need to implement something based on a model i allready know.
For instance this article only suggests 8 different thread communication approaches.
http://bighai.com/ppjava/?p=140
So all i need is someone who has experience in both languages to tell me which way is going to be easier for me to understand and implement.

I know it's wrong but i don't have the time to read entire books and get in depth knowledge of java.
I find it more helpful to try developing something and getting to know each concept on its own.

Thanks.

Hi everyone,

I am a C/C++ winapi developer and have to rewrite a "Dialog based" application in java, so that it will execute as an applet in any browser.

My java skills are very few, since my knowledge is limited to past college classes.

The application is not a large scale one, since it only implements a GUI, with a few screen interactions, which are driven by data from udp network connections.

In a windows development model, i would create worker threads wich handle the network communication and feed the gui with data through the window message queue, probably using SendMessage or PostMessage functions.

So my question is, how do i implement this kind of model in java?
I am not interested, for the time being, in learning another model of thread communication, i just want to know if there is anyway to apply the same model in java, because i am quite familiar with it.

Thanks in advance!

hi,i am a windows user ,but itf it were doing it to me i would rest the router ,should be a small button on the bottom or back ,you need to use a pointed object to push and hold it in till all the lights start flashing on the router

I would if i could go there, but i wouldn't recommend my novice friend that, fearing that it would loose any settings.

Check the time and date on her laptop. As well make sure she doesn't have any blocked ports or sites on her router. This all sounds like SSH acting up, so might as well check into any settings related to that as well.

This was the first thing i did since it happened to me a couple of times too. It was not the case...

Anyway i cannot imagine a way that the router could prevent access to certain websites from a specific operating system. Isn't it supposed to be transparent in the way it handles requests?
Do home routers have any kind of blacklisting policy that i am not aware of?

On the other hand it seems as the most possible point of failure so i am going to have to reset it.
I am just asking cause i would love to know what really goes on.
I am a geek...
:)

Hi everyone.
I am trying to help a friend with her macbook which faces a mysterious problem.
The macbook cannot access certain sites like facebook and pinterest when my friend uses her home wifi connection.
The problem appears both on safari and chrome.
When she came to my home using my wifi router both sites loaded perfectly so i assumed It was just a random problem. When she went back to hers, it happened again.
Sometimes the browser will pop a certificate error message and oher times just a blank page not loading anything.

The strange thing is that it happens only when using her home router and only on those websites, as far as i know.

I tried to clear browser cache and forcefully accept not valid certificates but no luck...

Any ideas?
Thanks.

This is a very good tutorial for mfc dialog based application beginers
http://www.codeproject.com/Articles/589/A-Beginners-Guide-to-Dialog-Based-Applications-Par

It's a 15 minute read and once you complete it i am sure you will be able to create a dialog with a button that executes some code. Also how to parse input from textboxes.

You could use your existing ascii drawing inside a textbox to create the feel of visual interaction, but if you want to use real images you will have to dig a little deeper by reading something like this:

http://www.codeproject.com/Articles/356/Bitmap-Basics-A-GDI-tutorial

Hope that helped.

C++ code seems ok, tested it my self and works without any exceptions. Of course my client is :
http://www.drk.com.ar/builder.php (you can download and check it with this one also)

Don't know about java, but you should ensure that your server's ip address is the one you typed and there is not a firewall in any of the machines that blocks port 8888.

Hope that helped!

I am not sure if this will help but take a look at this function as well:
http://msdn.microsoft.com/en-us/library/windows/desktop/aa385449(v=vs.85).aspx

Also if you are willing to sacrifice a little bit of modularity you could store all names in an array and remove the names which you are sure that are not neccessary.

Anyway i don't think that there's a way of instructing this api function to return specified results.

I have no idea of OpenGL but i think you should consider that adding an external monitor changes the hardware capabilities of your platform, thus changing the way that OpenGl "accesses" it.
Which might mean that either your OpenGl initialization is incorrect, or your hardware is not capable of handling the opengl settings you provide.
Of course that's what might happen in DirectX so this is just a shot in the dark...

Debug your application step by step and watch for any warnings when initalizing the opengl components.

Good luck!

p.s. If you plug your monitor and use "extended desktop mode" (you can see output on both monitors), try to change it to external monitor mode only, to see if that helps.

I would like you to check out a sample i made and give me any instructions of how i can increase performance.

Open this link :
http://www.psygnus.t15.org/reels_test.html

It simulates a slot machine reel spinning with the help of TweenJS library.

In the PC i am working right now (core 2 duo, 2GB RAM) it is tearing and flickers quite much.
Is there anyway to improve performance and eliminate (as much as possible) the flickering?

Can i use something like double buffering in HTML5/javascript or any other technique?

Any suggestions would be great!

Thanks!

It seems that using only javascript/html5 is not enough for producing high quality motion graphics.
It handles sprite animations quite impressively but it really struggles with moving objects.

BTW i used EASELJS library.

P.S. I mangaged to code 3 animations in a couple of hours without any previous knowledge, and i remember doing the same for the first time in DirectX... it took me almost a week...
:)

I have to try WebGL i suppose.. but i remember OpenGL being more difficult than DirectX and i am afraid of it..!

Thanks for the links!
Very useful for start.

So if use html5/javascript without WebGL (not supported by older Graphics Cards), do you think i will be able to produce a commercially acceptable product?

Because all i could find was experimental stuff.
Perhaps it is too soon to pick it as a proffessional solution...(?)

Thanks again!

Hello everyone!

I would like some suggestions on picking a game development technology/language.

My requirements are :
1) On line / Web based game only
2) 2d animation only (for the time being). Using mostly sprites and modelling only simple 2d shapes.
3) No need for an advanced physics engine. I am starting a slot machine game like http://www.youtube.com/watch?v=ZYOvcPnBi-A
4) Game should run on a browser only and not require a client side application to be installed.
5) Will run on windows OS machines exclusively.

My experience is :
1) More than 3 years experience of system/interface programming using C/C++/Visual C++/python
2) Basic knowledge of web programming PHP/HTML/CSS/MySQL
3) Little knowledge of DirectX programming.

I know that there are 2 basic rivals when it comes to on-line gaming. Flash/Actionscript and JAVA.
The company i work for has developed Flash and Java games. So there is code i can reuse/study.
But they abandoned Flash because it added too much overhad and was CPU intensive (at least 5 years ago).
So Java is my only choise now that i will start game development.
Or is it not????

Which brings me to my question:
Is there an alternative way to go in web based game development?
Is it worth the trouble?

I was thinking of a more open source way to go such as using only HTML5/Javasctipt, but i have no clue if there are any kind …

No problem..
I'm glad i helped!

You are correct. Forget about std library, it's c++ not c.
You can look here for a c library reference :
http://www.acm.uiuc.edu/webmonkeys/book/c_guide/

You can look here too
http://www.cplusplus.com/
This is one of the most complete c++ reference websites which of course contains most if not all of C language functions.

All you need to know about is the string library <string.h> and file streams <stdio.h>

You can use the following functions :
1. strtok to parse strings seperated by a token (';' in your case).
2. strcmp to compare if two strings are the same.

In a while loop you can use strtok to get each of your records' data and use a counter variable which will be increased every time you find the newline character ('\n').
Using strcmp you can compare each token with the string you are searching. The loop counter will have the line you are positioned in that case.
As for the column of the line you could use strlen on each token and add the lengths of the strings to get the column you are trying to alter.

Hope that helped!

Those two are open source projects which might help you getting started :
http://virtuawin.sourceforge.net/

http://virt-dimension.sourceforge.net/

as for screen sharing you could try :

http://obsproject.com/index
and of course :
http://www.videolan.org/vlc/

I have no previous experience personally but i am sure that you will get some help from those guys

For what it's worth both parts of a project like this are quite large, so doing it all by yourself might be a challenging task.
But that's why open source software is great!

I think it works like this.

They software is in fact a virtual desktop multi screen application
http://en.wikipedia.org/wiki/Virtual_desktop#Windows
combined with a screen sharing application
http://en.wikipedia.org/wiki/Desktop_sharing

The server side of the application captures the non-primary virtual desktops and sends a network stream to the clients, which are of course the other computers to which the desktop "extends" it self.

So in my opinion there is no "magic" graphics driver of any kind.

Hope this helps.

I don't have Borland installed but this might help you :

http://www.cplusplus.com/forum/beginner/3485/

Thanks a lot!
That's a really thorough explanation.

It seems like i will have to re-check my algorithmic design so... good luck to me!
:)

Thanks again!

So what about this case for example :

http://www.cs.umd.edu/~shankar/417-F01/Slides/chapter3b/sld007.htm

This is supposed to be a scenario of retransmission (?)

Ok thanks a lot JorgeM.

If anyone else has anything to contribute...

Otherwise i'm marking this as solved

Thanks JorgeM.

So could i suppose that tcp retransmission is a feature that i should deal programatically? Because i never thought of a scenario like that.

It seems that the client receives the packet, his ACK is not received by the server, and the server retransmits the packet. So the client receives 2 identical packets which is probably not handled well by my application.

Is the above scenario plausible in tcp connections or is this my misundestanding?

Hello everyone!

I have a server/client application running in 4 internet cafes, and i have a packet duplication problem in one of them.

I have thoroughly examined my code and tested it in my lab and cannot find any bugs whatsoever.
So on rare conditions some of the clients seems to receive duplicate packets. (I installed wireshark to investigate the problem in the specific shop).
I am not sure if this is causing my application to crash but i have nothing else to blame!
:)

So the question :

**Is there any chance that faulty hardware (router, switches, NICs) or bad drivers can cause packet duplication or packet corruption?? I even thought of viruses but firewall and antivirus software is enabled in all machines.
**
I am in a dead end and cannot think of anything here... If the problem wasn't in a specific shop only, i would re-examine my code but..

Thanks in advance!