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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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• What is the impact/limitation of oracle select with large number of bind variables?

  - by Igal Serban

  We had our oracle server chocking during processing a select statement with close to 3500(!!) bind variables. This select is, obviously, build dynamically by code that we can't change. During the execution of this select the db server went to 100% cpu usage and our system almost halted. We know how to reproduce this problem. So we can prevent this specific condition. But I am wondering if there is a way to protect the db ( by configuration) from this type of problems.

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• Practical Python-based visual programming environment?

  - by Who8MyLunch

  I am looking for a practical visual programming environment based on Python. My primary application is algorithm development for processing remote-sensing imagery. I was initially inspired by LabVIEW from National Instruments, but that is more geared towards laboratory measurements and simulations. I write a lot of prototype code in Python and do a lot of interactive analysis with IPython. Does there exist a visual framework where a "program" is represented by connected nodes which each read data, do some work, and output data to the next node? I would like to use Python to write the code residing in each node. So far the best I've seen is Orange http://www.ailab.si/orange/, but it does not have the ability to start/stop individual nodes.

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• How to Communicate between minifb and a GAE-Hosted Silverlight Client

  - by Nick Gotch

  I have a minifb app (technically gminifb) running on Google App Engine with a bunch of handlers for processing all kinds of requests from a Silverlight client. What's the recommended approach for adding the FB GET variables, such as fb_sig, to the HTTP requests? I believe I can technically pass the session key and uid directly and get things to work but it seems there's probably a much better way to do this. I was reading about FBJS AJAX and I'm trying to figure out how I can use it to proxy the HTTP requests from the Silverlight client through it. Is this a good way to do it? And if so, how would I go about doing so? Any other recommendations would be appreciated too. Thanks,

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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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• How can I request local pages in the background of an ASP.NET MVC app?

  - by flipdoubt

  My ASP.NET MVC app needs to run a set of tasks at startup and in the background at a regular interval. I have implemented each task as a controller action and listed the app-relative path to the action in the database. I implemented a TaskRunner process that gets the urls from the database and requests each one at a regular interval using WebRequest.Create, but this throws a UriFormatException. I cannot use this answer or any code that plucks values from HttpContext.Current.Request without getting an HttpException with the message "Request is not available in this context". The Request object is not available because my code uses System.Threading.Timer to do background processing, as recommended here. Here are my questions: Is there really no way to make local web requests within an ASP.NET web app? Is there really no way to dynamically ascertain the root path to the web app even using static dependencies in ASP.NET? I was trying to avoid storing the app's root path in the database (as FogBugz does with its "Maintenance Path"), but is this best option?

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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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• Can getAttribute() method of Tomcat ServletContext implementation be called without synchronization?

  - by oo_olo_oo

  I would like to read some parameters during servlet initializtion (in init() method), and store them among servlet context attributes (using getServletContext().setAttribute()). I would like to read these parameters later - during some request processing (using getServletContext().getAttribute()). So, the multiple threads could do this simultaneously. My question is if such an attempt is safe? Could I be sure that multi threaded calls to the getAttribute() don't mess up any internal state of the servlet context? Please take into account that I'm not going to call the setAttribute() anywhere besides the initialization. So, only calls to the getAttribute() are going to be done from multiple threads. But depending on the internal implementation, this also could be dangerous. So, any information about Tomcat's implementation would be appreciated.

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• How to set a __str__ method for all ctype Structure classes?

  - by Reuben Thomas

  [Since asking this question, I've found: http://www.cs.unc.edu/~gb/blog/2007/02/11/ctypes-tricks/ which gives a good answer.] I just wrote a __str__ method for a ctype-generated Structure class 'foo' thus: def foo_to_str(self): s = [] for i in foo._fields_: s.append('{}: {}'.format(i[0], foo.\_\_getattribute__(self, i[0]))) return '\n'.join(s) foo.\_\_str__ = foo_to_str But this is a fairly natural way to produce a __str__ method for any Structure class. How can I add this method directly to the Structure class, so that all Structure classes generated by ctypes get it? (I am using the h2xml and xml2py scripts to auto-generate ctypes code, and this offers no obvious way to change the names of the classes output, so simply subclassing Structure, Union &c. and adding my __str__ method there would involve post-processing the output of xml2py.)

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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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• Determining Excel spreadsheet format before Data Flow Task

  - by Josh Larsen

  I'm working on an SSIS package which uses a for each loop to iterate through excel files in a directory and a data flow task to import them. The issue I'm having is that the project manager I'm working with doesn't think the users will always follow the structure. So if a file is in the folder and the package tries to import it but the spreadsheet is missing columns or has extra columns it generates and error of course. Even though I have the task set to not fail the package; the package does indeed fail and then the other files aren't imported. So, I'm wondering what is the easiest way to either determine the spreadsheet is incorrectly formatted, or stop the error from failing the package execution? After taking said step I would just use a file copy task to move the file to a "Failure" folder. Then continue on processing the spreadsheets.

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• Where would async calls make sense in an ASP.net (MVC) Web Application?

  - by Michael Stum

  I'm just wondering, if I have an ASP.net Web Application, either WebForms or MVC, is there any situation where doing stuff asynchronously would make sense? The Web Server already handles threading for me in that it spins up multiple threads to handle requests, and most request processing is rather simple and straight forward. I see some use for when stuff truly is a) expensive and b) can be parallelized. but these are the minority cases (at least from what I've encountered). Is there any gain from async in the simple "Read some input, do some CRUD, display some output" scenario?

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• Ref to map vs. map to refs vs. multiple refs

  - by mikera

  I'm working on a GUI application in Swing+Clojure that requires various mutable pieces of data (e.g. scroll position, user data, filename, selected tool options etc.). I can see at least three different ways of handling this set of data: Create a ref to a map of all the data: (def data (ref { :filename "filename.xml" :scroll [0 0] })) Create a map of refs to the individual data elements: (def datamap { :filename (ref "filename.xml") :scroll (ref [0 0]) })) Create a separate ref for each in the namespace: (def scroll (ref [0 0])) (def filename (ref "filename.xml")) Note: This data will be accessed concurrently, e.g. by background processing threads or the Swing event handling thread. However there probably isn't a need for consistent transactional updates of multiple elements. What would be your recommended approach and why?

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• Problem with detecting phone orientation change in Symbian/Qt

  - by trex279

  I want to do some custom processing when the orientation of the phone changes. I have re-implemented the resizeEvent(QResizeEvent*) virtual function in my class. The strange thing is, for the first one time when the phone orientation is changed, this function is actually called, and works fine. But all subsequent orientation changes, this function isn't even called? Why does this happen? Are there any other ways to detect phone orientation change? Thanks.

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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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• In html <a href> tag, how to call servlet before opening file dialog for download (save as)?

  - by deepthinker121

  Hi All, I am developing a web-app where I want to provide a download link to users - so they can download a zip file from my server. Now, my requirement is that I want to execute some processing logic contained in a servlet before displaying the file dialog to the user for 'zip' files. So If I write <a href="abc.zip".......> then it opens a file dialog asking the user to select the location where this file can be saved But if I want a servlet's doGet method to do some preprocessing - say like building the zip file , then how can I first call the servlet and then open the file dialog. Will the following snippet work? <a href="MyHandlerServlet;abc.zip".......> Thanks for your help !!

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• how to test if a string is a valid UTF16 string?

  - by superb

  I am using mongodb and javascript to do some string processing. Now I got some error like: Sun May 23 07:42:20 Assertion failure JS_EncodeCharacters( _context , s , srclen , dst , &len) scripting/engine_spidermonkey.cpp 152 0x80f4f7e 0x80f8794 0x811525b 0x811a953 0x8119fc4 0x8111bc5 0x81b408e 0x81c4ee7 0x81b4a10 0x817a881 0x817a7d8 0x817a6e2 0x811e1bb 0x80a777b 0x80a8f8a 0xb7cb2455 0x80a37a1 mongodb-linux-i686-1.4.2/bin/mongo(_ZN5mongo12sayDbContextEPKc+0xfe) [0x80f4f7e] After doing some google, I find that JS_EncodeCharacters return false if the input is not a valid UTF16 string. (if spidermonkey is build with UTF-8 enabled) So I was wondering how to test if the input string if a proper UTF16 string? so I can skip such kind of string to avoid problem ... Thanks

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• How to read GPU (graphic card) temperature?

  - by mr.b

  I am interested in a way how to read GPU temperature (graphics processing unit, main chip of graphic card), by using some video card driver API? Everyone knows that there two different chip manufacturers (popular ones, at least) - ATI and nVIDIA - so there are two different kinds of drivers to read temperature from. I'm interested in learning how to do it for each different card driver. Language in question is irrelevant - it could be C/C++, .NET platform, Java, but let's say that .NET is preferred. Anyone been doing this before?

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• Letting Wcf data service implement another contract

  - by Wasim

  Hi all , I have a wcf data service with the standart configuration . I want to add another functionality to it , so I built a contract interface and let my wcf data service implements it . Now I see in the service the InitializeService method , and the contract interface methods . When I come to connect the service , I get an error , that there is no end point declared to the contract I added . How can do that ? examples ? links ? I choosed to add the contract interface to the wcf data service and not adding another service , because the client application uses the wcf data service generated objects , and I want to use the same obkject to make operations not related to data , for more coplex processing . If I do the methods in another service , then I have types incompatibility . Thanks in advance ...

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• Integrating Prolog with C#

  - by TK

  Does anyone know of a nice (and preferably free) way to integrate Prolog and C#? Im looking to create a Prolog dll or similar to call from my managed code, and retrieve an answer once all the processing has been complete. Im looking for it to be predominantly one sided (c# calls Prolog). I have seen this question which talks about Prologs real world usage but I was wondering if anyone had either any experience with c# & Prolog? or a nice tutorial/article?

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• Threading calls to web service in a web service - (.net 2.0)

  - by Ryan Ternier

  Got a question regarding best practices for doing parallel web service calls, in a web service. Our portal will get a message, split that message into 2 messages, and then do 2 calls to our broker. These need to be on separate threads to lower the timeout. One solution is to do something similar to (pseudo code): XmlNode DNode = GetaGetDemoNodeSomehow(); XmlNode ENode = GetAGetElNodeSomehow(); XmlNode elResponse; XmlNode demResponse; Thread dThread = new Thread(delegate { //Web Service Call GetDemographics d = new GetDemographics(); demResponse = d.HIALRequest(DNode); }); Thread eThread = new Thread(delegate { //Web Service Call GetEligibility ge = new GetEligibility(); elResponse = ge.HIALRequest(ENode); }); dThread.Start(); eThread.Start(); dThread.Join(); eThread.Join(); //combine the resulting XML and return it. //Maybe throw a bit of logging in to make architecture happy Another option we thought of is to create a worker class, and pass it the service information and have it execute. This would allow us to have a bit more control over what is going on, but could add additional overhead. Another option brought up would be 2 asynchronous calls and manage the returns through a loop. When the calls are completed (success or error) the loop picks it up and ends. The portal service will be called about 50,000 times a day. I don't want to gold plate this sucker. I'm looking for something light weight. The services that are being called on the broker do have time out limits set, and are already heavily logged and audited, so I'm not worried on that part. This is .NET 2.0 , and as much as I would love to upgrade I can't right now. So please leave all the goodies of 2.0 out please.

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• What does MySqlDataAdapter.Fill return when the results are empty?

  - by Brian

  I have a 'worker' function that will be processing any and all sql queries in my program. I will need to execute queries that return result sets and ones that just execute stored procedures without any results. Is this possible with MySqlDataAdapter.Fill or do I need to use the MySqlCommand.ExecuteNonQuery() method? Here is my 'worker' function for reference: private DataSet RunQuery(string SQL) { MySqlConnection connection; MySqlCommand command; MySqlDataAdapter adapter; DataSet dataset = new DataSet(); lock(locker) { connection = new MySqlConnection(MyConString); command = new MySqlCommand(); command = connection.CreateCommand(); command.CommandText = SQL; adapter = new MySqlDataAdapter(); adapter.Fill(dataset); } return dataset; }

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• Python: Unpack arbitary length bits for database storage

  - by sberry2A

  I have a binary data format consisting of 18,000+ packed int64s, ints, shorts, bytes and chars. The data is packed to minimize it's size, so they don't always use byte sized chunks. For example, a number whose min and max value are 31, 32 respectively might be stored with a single bit where the actual value is bitvalue + min, so 0 is 31 and 1 is 32. I am looking for the most efficient way to unpack all of these for subsequent processing and database storage. Right now I am able to read any value by using either struct.unpack, or BitBuffer. I use struct.unpack for any data that starts on a bit where (bit-offset % 8 == 0 and data-length % 8 == 0) and I use BitBuffer for anything else. I know the offset and size of every packed piece of data, so what is going to be the fasted way to completely unpack them? Many thanks.

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• How to avoid exceptions catches copy-paste in .NET

  - by Budda

  Working with .NET framework I have a service with a set of methods that can generates several types of exceptions: MyException2, MyExc1, Exception... To provide proper work for all methods, each of them contains following sections: void Method1(...) { try { ... required functionality } catch(MyException2 exc) { ... process exception of MyException2 type } catch(MyExc1 exc) { ... process exception of MyExc1 type } catch(Exception exc) { ... process exception of Exception type } ... process and return result if necessary } It is very boring to have exactly same stuff in EACH service method with exactly same exceptions processing functionality... Is there any possibility to "group" these catch-sections and use only one line (something similar to C++ macros)? Probably something new in .NET 4.0 is related to this topic? Thanks. P.S. Any thoughts are welcome.

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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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