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• multiple clients - one server connection with sockets tcp/ip c# .net

  - by jagse

  Hello guys, I need to develop a client server system where I can have multiple clients communicating with one server at the same time. I want to communicate xml serialized objects and also need to send and receive other commands to invoke methods. Now, I am just starting with socket programming in C# and .Net and found that the asynchronous I/O is the way to go so that the methods dont block the execution of code. Also there are many examples of how to make a simple client server system. So I have a basic understanding of how that works. Anyway, what still is not clear to me is how I can set up a server which can manage connections to multiple clients? Can I just create a new socket per connection and then store those in some kind of list? Do I need some kind of multiplexing to achieve this? Do I have to listen at multiple ports? What`s the best way here? And the other thing is if I need to develop my own protocol to differentiate between what I am actually sending over the network -- xml serialized object or a command which might be just a string encoded in ascII or something. Or would I develop my own protocol just to send these commands? Any kind of help is apreciated! If someone knows a good book which covers this sort of stuff, let me know. Cheers I forgot to mention that some of my clients which are supposed to communicate with my server will be pda and I therefore use the compact framework... So this might bring in some restrictions...

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• long running process in asp.net C#

  - by user339323

  Hello All, I have a web application that has a long running (resource intensive) process in the code behind and the end output is a pdf file (images to pdf conversion tool) It runs fine..and since I am on a dedicated server, it is not at all a problem with respect to resources right now. However, I wonder that the system would reach its resource limits if, there are more than 20 users processing at a time. I have seen services online where the user enters their email and the processes are, I suppose, queued in the background and the results emailed with the 1st in 1st out method. Can someone please give me a start on how to implement this kind of logic in asp.net applications using C#? Thanks a lot in advance, Prasad.

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• Time order of messages

  - by Aiden Bell

  Read (skimmed enough to get coding) through Erlang Programming and Programming Erlang. One question, which is as simple as it sounds: If you have a process Pid1 on machine m1 and a billion million messages are sent to Pid1, are messages handled in parallel by that process (I get the impression no) and(answered below) is there any guarantee of order when processing messages? ie. Received in order sent? If so, how is clock skew handled in high traffic situations for ordering? Coming from the whole C/Thread pools/Shared State background ... I want to get this concrete. I understand distributing an application, but want to ensure the 'raw bones' are what I expect before building processes and distributing workload. Also, am I right in thinking the whole world is currently flicking through Erlang texts ;)

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• Passing HttpFileCollectionBase to the Business Layer - Bad?

  - by Terry_Brown

  hopefully there's an easy solution to this one. I have my MVC2 project which allows uploads of files on certain forms. I'm trying to keep my controllers lean, and handle the processing within the business layer of this sort of thing. That said, HttpFileCollectionBase is obviously in the System.Web assembly. Ideally I want to call to something like: UserService.SaveEvidenceFiles(MyUser user, HttpFileCollectionBase files); or something similar and have my business layer handle the logic of how and where these things are saved. But, it feels a little icky to have my models layer with a reference to System.Web in terms of separation of concerns etc. So, we have (that I'm aware of) a few options: the web project handling this, and my controllers getting fatter mapping the HttpFileCollectionBase to something my business layer likes passing the collection through, and accepting that I reference System.Web from my business project Would love some feedback here on best practice approaches to this sort of thing - even if not specifically within the context of the above.

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• CImg compile problems in Codegear 2009

  - by Seth

  I wish to use the CImg library for image processing in my current project. I am using Codegear C++ Builder 2009. I include CImg.h in the source file and put in the following code: int rows =5; int cols = 5; CImg<double> img(rows,cols); I get the following error: [BCC32 Error] CImg.h(39159): E2285 Could not find a match for 'CImg<unsigned char>::move_to<t>(const CImg<unsigned char>)' Does anyone know if there is a #define I should be using when building in Codegear C++ Builder 2009. Or is it simply not compatible?

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• What to beware of reading old Numarray tutorials and examples?

  - by DarenW

  Python currently uses Numpy for heavy duty math and image processing. The earlier Numeric and Numarray are obsolete, but still today there are many tutorials, notes, sample code and other documentation using them. Some of these cover special topics of interest, some are well written but haven't been updated or replaced, or are otherwise of use. Quite a bit is the same between Numeric, Numarray and Numpy, so I usually get good mileage out these older docs. Ocassionaly, though, I run into a line of code that results in error. Not often enough to remember how to get around it, but usually I figure it out at the cost of some time. What are the main things to watch out for when relying on such older documentation for current Numpy use? Is there a list of how to translate the differences that exist?

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• What do we need for flash 10 development?

  - by user246114

  Hi, I'm looking to do some development in flash 10, specifically for the new file api (reading/writing files on the user's local machine). What do I need to develop for flash 10, just Flash cs4?: http://tryit.adobe.com/us/cs4/flash/c/?sdid=ETJMX& or is there some other ide? All I'm really interested in doing is: Make a small swf file which reads a file on the user's machine I will host it in an html file When file read is done, I just want to send its contents as a string to a javascript function for further processing. Not sure if I can get away with the free adobe air thing for this? I need it to run in a webpage but I don't intend to do any more development outside of the above, Thanks

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• JAVA: 500 Worker Threads, what kind of thread pool?

  - by Submerged

  I am wondering if this is the best way to do this. I have about 500 threads that run indefinitely, but Thread.sleep for a minute when done one cycle of processing. ExecutorService es = Executors.newFixedThreadPool(list.size()+1); for (int i = 0; i < list.size(); i++) { es.execute(coreAppVector.elementAt(i)); //coreAppVector is a vector of extends thread objects } I do need a separate threads for each running task, so changing the architecture isn't an option. I tried making my threadPool size equal to Runtime.getRuntime().availableProcessors() which attempted to run all 500 threads, but only let 8 (4xhyperthreading) of them execute. The other threads wouldn't surrender and let other threads have their turn. I tried putting in a wait() and notify(), but still no luck. If anyone has a simple example or some tips, I would be grateful!

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• Using exponential smoothing with NaN values

  - by Eric

  I have a sample of some kind that can create somewhat noisy output. The sample is the result of some image processing from a camera, which indicates the heading of a blob of a certain color. It is an angle from around -45° to +45°, or a NaN, which means that the blob is not actually in view. In order to combat the noisy data, I felt that exponential smoothing would do the trick. However, I'm not sure how to handle the NaN values. On the one hand, involving them in the math would result in a NaN average, which would then prevent any meaningful results. On the other hand, ignoring NaN values completely would mean that a "no-detection" scenario would never be reported. And just to complicate things, the data is also noisy in that it can get false NaN value, which ideally would be smoothed somehow to prevent random noise. Any ideas about how I could implement such an exponential smoother?

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• Sending a list of mails with SmtpClient

  - by Malcolm Frexner

  I use SendCompletedEventHandler of SmtpClient when sending a list of emails. The SendCompletedEventHandler is only called when have already sent all emails in the list. I expexted, that SendCompletedEventHandler is called one an email is send. Is there something wrong in my code? public void SendAllNewsletters(List<string> recipients) { string mailText = "My Tex"; foreach(string recipient in recipients) { //if this loop takes 10min then the first call to //SendCompletedCallback is after 10min SendNewsletter(mailText,recipient); } } public bool SendNewsletter(string mailText , string emailaddress) { SmtpClient sc = new SmtpClient(_smtpServer, _smtpPort); System.Net.NetworkCredential SMTPUserInfo = new System.Net.NetworkCredential(_smtpuser, _smtppassword); sc.Credentials = SMTPUserInfo; sc.SendCompleted += new SendCompletedEventHandler(SendCompletedCallback); MailMessage mm = null; mm = new MailMessage(mailText, emailaddress); mm.IsBodyHtml = true; mm.Priority = MailPriority.Normal; mm.Subject = "Something"; mm.Body = "Something"; mm.SubjectEncoding = Encoding.UTF8; mm.BodyEncoding = Encoding.UTF8; //Mail string userState = emailaddress; sc.SendAsync(mm, userState); return true; } public void SendCompletedCallback(object sender, AsyncCompletedEventArgs e) { // Get the unique identifier for this asynchronous operation. String token = (string)e.UserState; if (e.Error != null) { _news.SetNewsletterEmailsisSent(e.UserState.ToString(), _newslettername, false, e.Error.Message); } else { _news.SetNewsletterEmailsisSent(e.UserState.ToString(), _newslettername, true, string.Empty); } }

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• How to return the full file path in a C# / ASP.NET web application?

  - by salvationishere

  This should be really simple, but I have tried many solutions posted on the internet so I thought I'd give this a try here. I have a VS 2008 web application that I need to capture the full file path (directories and file name) from the selected file. So user selects a file and then clicks on one of the buttons which transfers control to my code for processing. So how do I get the file path? I can get the file name, but not the path. Thanks!

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• How can I asynchronously monitor a file in Perl?

  - by Hussain

  I am wondering if it is possible, and if so how, one could create a perl script that constantly monitors a file/db, and then call a subroutine to perform text processing if the file is changed. I'm pretty sure this would be possible using sockets, but this needs to be used for a webchat application on a site running on a shared host, and I'm not so sure sockets would be allowed on it. The basic idea is: create a listener for a chat file/database when the file is updated with a new message, call a subroutine the called subroutine will send the new message back to the browser to be displayed Thanks in advance.

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• Matlab: How to find the right-most point of a white line within the imrect?

  - by mchlfchr

  i've got a question regarding the imrect() function, which is part of the image processing toolbox in MatLab. I'd like to find a starting point within an image. I use the imrect function for setting a region to limit and specify the lookup area, but I can't get the point where the ROI mask is getting back mapped to the original size of the image. As you can see on the image there is a specified rectangle (cyan-colored), which I want to inspect for the white line, especially the nearest point to the right edge of the rectangle. I experimentated with only looking up on the last column of the rectangle, but as I mentioned before, the re-mapping onto the global image coordinates failed. So in this example, the white point I'd like to get would be around (98,302) The original (x,y) coordinates are relevant, so a cropping of the image to the rectangle is not acceptable. So, do you have any ideas? Thanks for any helping comments. Kind regards,

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• ContextSwitchDeadlock Was Detected error in C#

  - by assassin

  Hi, I am running a C# application, and during run-time I get the following error: The CLR has been unable to transition from COM context 0x20e480 to COM context 0x20e5f0 for 60 seconds. The thread that owns the destination context/apartment is most likely either doing a non pumping wait or processing a very long running operation without pumping Windows messages. This situation generally has a negative performance impact and may even lead to the application becoming non responsive or memory usage accumulating continually over time. To avoid this problem, all single threaded apartment (STA) threads should use pumping wait primitives (such as CoWaitForMultipleHandles) and routinely pump messages during long running operations. Can anyone please help me out with the problem here? Thanks a lot.

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• Batch file writing to log then ending process

  - by Andrew Service

  I have a batch file that calls a process and in that process I have: IF %ERRORLEVEL% NEQ 0 EXIT /B %ERRORLEVEL% Now I wanted to upgrade this a bit and give some meaningful message to an output log when if the process fails, also I do not want the main batch to continue processing because the next processes are dependent on data from previous calls; I wonder if this would be correct but not sure: CALL Process 1 IF %ERRORLEVEL% NEQ 0 GOTO ErrorInfirstProcess /B %ERRORLEVEL% :ErrorInfirstProcess ECHO Process 1 Failed on %Date% at %Time%. >>C:\Log.txt" CALL Process 2 IF %ERRORLEVEL% NEQ 0 GOTO ErrorInSecondProcess /B %ERRORLEVEL% :ErrorInSecondProcess ECHO Process 2 Failed on %Date% at %Time%. >>C:\Log.txt" I also want to know if I still need the /B or do I need to put an EXIT command after the echo? Thanks A

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• Windows Platform Installer fails during Orchard Installation

  - by nullnvoid

  I'm attempting to install Orchard 1.0 on a Windows 7 box. It has only just been released. I downloaded and installed the Windows Platform Installer and attempted to install Orchard. The error message is just that the application has stopped working and asks if I want to debug or close the application. The event log contains a single error: "The event logging service encountered an error while processing an incoming event published from Microsoft-Windows-Security-Auditing." I tried installing MVC3 and it worked without issue. Has anyone experienced a similar problem?

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• Can I prevent a Linux user space pthread yielding in critical code?

  - by KermitG

  I am working on an user space app for an embedded Linux project using the 2.6.24.3 kernel. My app passes data between two file nodes by creating 2 pthreads that each sleep until a asynchronous IO operation completes at which point it wakes and runs a completion handler. The completion handlers need to keep track of how many transfers are pending and maintain a handful of linked lists that one thread will add to and the other will remove. // sleep here until events arrive or time out expires for(;;) { no_of_events = io_getevents(ctx, 1, num_events, events, &timeout); // Process each aio event that has completed or thrown an error for (i=0; i<no_of_events; i++) { // Get pointer to completion handler io_complete = (io_callback_t) events[i].data; // Get pointer to data object iocb = (struct iocb *) events[i].obj; // Call completion handler and pass it the data object io_complete(ctx, iocb, events[i].res, events[i].res2); } } My question is this... Is there a simple way I can prevent the currently active thread from yielding whilst it runs the completion handler rather than going down the mutex/spin lock route? Or failing that can Linux be configured to prevent yielding a pthread when a mutex/spin lock is held?

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• How HID devices work when programming?

  - by user1008476

  I have a barcode scanner works as HID device. Everytime a barcode scans it goes directly to windows keyboard, for example if I open notepad I can see the barcode typed there. As far as I know programmatically is it possible to to read HID data from your HID devices. But what happens if the user is already on a form with a text edit control? The scanned code will go inside the text box. Can you block incoming text and make a background-only processing? Can you explain the theory please?

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• Improving the join of two wave file?

  - by kaki

  I have written a code for joining two wave files.It works fine when i am joining larger segments but as i need to join very small segments the clarity is not good. I have learned that the signal processing technique such a windowed join can be used to improve the joining of file. y[n] = w[n]s[n] Multiply value of signal at sample number n by the value of a windowing function hamming window w[n]= .54 - .46*cos(2*Pi*n)/L 0 I am not understanding how to get the value to signal at sample n and how to implement this?? the code i am using for joining is import wave m=['C:/begpython/S0001_0002.wav', 'C:/begpython/S0001_0001.wav'] i=1 a=m[i] infiles = [a, "C:/begpython/S0001_0002.wav", a] outfile = "C:/begpython/S0001_00367.wav" data= [] data1=[] for infile in infiles: w = wave.open(infile, 'rb') data1=[w.getnframes] data.append( [w.getparams(), w.readframes(w.getnframes())] ) #data1 = [ord(character) for character in data1] #print data1 #data1 = ''.join(chr(character) for character in data1) w.close() output = wave.open(outfile, 'wb') output.setparams(data[0][0]) output.writeframes(data[0][1]) output.writeframes(data[1][1]) output.writeframes(data[2][1]) output.close()

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• classic asp & .net 2 site not working on windows 7

  - by alexander2116

  I am receiving the following error message: An error occurred on the server when processing the URL. Please contact the system administrator. If you are the system administrator please click here to find out more about this error. I have my site in the inetpub directory in a subfolder called website. I have also gone to add/remove windows compononents and had asp installed. In iss manager I have asp listed with defult settings. The initial website page is a classic asp page Has anyone else encountered this issue? Please help! I'm having to develop through vpn/remote desktop combo which is painfully slow!! thanks so much for anyone who can help!

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• Best option for Google App Engine Datastore and external database?

  - by Alex

  I need to get an App Engine app talking to and sharing data with an external database, The best option i can come up with is outputting the external database data to an xml file and then processing this in my app engine app and storing it inside the datastore, although the data being shared is sensitive data such as login details so outputting this to an xml file is not exactly a great idea, is it possible for the app engine app to directly query the database? or is there a secure option for using xml files? oh and im using python/django and the external database will be hosted on another domain

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• How do I control script execution time in PHP

  - by mathew

  for example I do have 5 PHP functions on a page which execute when loading. each functions has its own processing time and some of them take more time sometimes to complete the task. hence the total loading time of the said page is slow. my question is how do I control execution time for each script and set time limit for the same. I am aware that there is an in built function in PHP called set_time_limit(); but it gives fatal error if time is beyond the maximum limit...

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• how to set style through javascript in IE immediately

  - by rezna

  Hi, recently I've encountered a problem with IE. I have a function function() { ShowProgress(); DoSomeWork(); HideProgress(); } where ShowProgress and HideProgress just manipulate the 'display' CSS style using jQuery's css() method. In FF everything is OK, and at the same time I change the display property to block, progress-bar appears. But not in IE. In IE the style is applied, once I leave the function. Which means it's never shown, because at the end of the function I simply hide it. (if I remove the HideProgress line, the progress-bar appears right after finishing executing the function (more precisely, immediately when the calling functions ends - and so there's nothing else going on in IE)). Has anybody encountered this behavior? Is there a way to get IE to apply the style immediately? I've prepared a solution but it would take me some time to implement it. My DoSomeWork() method is doing some AJAX calls, and these are right now synchronous. I assume that making them asynchronous will kind of solve the problem, but I have to redesign the code a bit, so finding a solution just for applying the style immediately would much simplier. Thanks rezna

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• how to write silverlight threading function in another file or project

  - by Piyush

  I am using three tier architecture.I have SilverlightUI and UIController two projects.SilverlightUI contains only UI pages and controls while UIController contains all proxies of WCF services. Now I have created threads to update my controls dynamically and to do processing parallel.AS the requirement I want to define all functionality of threads in UIController projects.What should I do? Currenty what I am doing - private void Button_Click(object sender, RoutedEventArgs e) { StartThreads(); } private void StartThreads() { private Thread _thread1; _thread1 = new Thread(DoThread1); _thread1.Start(); } public static void DoThread1() { _data1.Dispatcher.BeginInvoke(delegate() { _data1.Text = _count1.ToString(); }); System.Threading.Thread.Sleep(1000); } I Want to write DoThread1() method in UIController project and call that function from here button_click()

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• Communication between lexer and parser

  - by FredOverflow

  Every time I write a simple lexer and parser, I stumble upon the same question: how should the lexer and the parser communicate? I see four different approaches: The lexer eagerly converts the entire input string into a vector of tokens. Once this is done, the vector is fed to the parser which converts it into a tree. This is by far the simplest solution to implement, but since all tokens are stored in memory, it wastes a lot of space. Each time the lexer finds a token, it invokes a function on the parser, passing the current token. In my experience, this only works if the parser can naturally be implemented as a state machine like LALR parsers. By contrast, I don't think it would work at all for recursive descent parsers. Each time the parser needs a token, it asks the lexer for the next one. This is very easy to implement in C# due to the yield keyword, but quite hard in C++ which doesn't have it. The lexer and parser communicate through an asynchronous queue. This is commonly known under the title "producer/consumer", and it should simplify the communication between the lexer and the parser a lot. Does it also outperform the other solutions on multicores? Or is lexing too trivial? Is my analysis sound? Are there other approaches I haven't thought of? What is used in real-world compilers? It would be really cool if compiler writers like Eric Lippert could shed some light on this issue.

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