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  • Perl TCP Server handling multiple Client connections

    - by Matt
    I'll preface this by saying I have minimal experience with both Perl and Socket programming, so I appreciate any help I can get. I have a TCP Server which needs to handle multiple Client connections simultaneously and be able to receive data from any one of the Clients at any time and also be able to send data back to the Clients based on information it's received. For example, Client1 and Client2 connect to my Server. Client2 sends "Ready", the server interprets that and sends "Go" to Client1. The following is what I have written so far: my $sock = new IO::Socket::INET { LocalHost => $host, // defined earlier in code LocalPort => $port, // defined earlier in code Proto => 'tcp', Listen => SOMAXCONN, Reuse => 1, }; die "Could not create socket $!\n" unless $sock; while ( my ($new_sock,$c_addr) = $sock->accept() ) { my ($client_port, $c_ip) = sockaddr_in($c_addr); my $client_ipnum = inet_ntoa($c_ip); my $client_host = ""; my @threads; print "got a connection from $client_host", "[$client_ipnum]\n"; my $command; my $data; while ($data = <$new_sock>) { push @threads, async \&Execute, $data; } } sub Execute { my ($command) = @_; // if($command) = "test" { // send "go" to socket1 print "Executing command: $command\n"; system($command); } I know both of my while loops will be blocking and I need a way to implement my accept command as a thread, but I'm not sure the proper way of writing it.

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  • In Asp.net (c#) i'm not able to catch any exception properly????

    - by Anand
    In Asp.net (c#),i'm not able to catch exception(FileNotFoundException) properly... i don't know the reason..Actually File s not there..But catch statement fails to catch the exception.. here is the code.. try { System.Drawing.Image imgg1 = System.Drawing.Image.FromFile(Server.MapPath("").ToString() + "\\images\\img1.jpg"); } catch (FileNotFoundException) { Response.Write("<script>alert('Please Select and upload Student's Photo');</script>"); }

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  • Returning JSON or XML for Exceptions in Jersey

    - by Dominic
    My goal is to have an error bean returned on a 404 with a descriptive message when a object is not found, and return the same MIME type that was requested. I have a look up resource, which will return the specified object in XML or JSON based on the URI (I have setup the com.sun.jersey.config.property.resourceConfigClass servlet parameter so I dont need the Accept header. My JAXBContextResolver has the ErrorBean.class in its list of types, and the correct JAXBContext is returned for this class because I can see in the logs). eg: http://foobar.com/rest/locations/1.json @GET @Path("{id}") @Produces({MediaType.APPLICATION_JSON, MediaType.APPLICATION_XML}) public Location getCustomer(@PathParam("id") int cId) { //look up location from datastore .... if (location == null) { throw new NotFoundException("Location" + cId + " is not found"); } } And my NotFoundException looks like this: public class NotFoundException extends WebApplicationException { public NotFoundException(String message) { super(Response.status(Response.Status.NOT_FOUND). entity(new ErrorBean( message, Response.Status.NOT_FOUND.getStatusCode() ) .build()); } } The ErrorBean is as follows: @XmlRootElement(name = "error") public class ErrorBean { private String errorMsg; private int errorCode; //no-arg constructor, property constructor, getter and setters ... } However, I'm always getting a 204 No Content response when I try this. I have hacked around, and if I return a string and specify the mime type this works fine: public NotFoundException(String message) { super(Response.status(Response.Status.NOT_FOUND). entity(message).type("text/plain").build()); } I have also tried returning an ErrorBean as a resource. This works fine: {"errorCode":404,"errorMsg":"Location 1 is not found!"}

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  • How to pass non-fatal warnings from a library

    - by wRAR
    A library function parses a file and returns an object. If a parser encounters unknown data, missing values etc., it shouldn't throw an exception and stop parsing (because this is not fatal), but there should be a way to pass information about these things to a caller (so that warnings can be displayed in the UI, for example). How can these warning be returned? I'm thinking of passing a callback function/object into the library, are there any other possible solutions?

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  • Java File Handling, what did I do wrong?

    - by Urda
    Wrote up a basic file handler for a Java Homework assignment, and when I got the assignment back I had some notes about failing to catch a few instances: Buffer from file could have been null. File was not found File stream wasn't closed Here is the block of code that is used for opening a file: /** * Create a Filestream, Buffer, and a String to store the Buffer. */ FileInputStream fin = null; BufferedReader buffRead = null; String loadedString = null; /** Try to open the file from user input */ try { fin = new FileInputStream(programPath + fileToParse); buffRead = new BufferedReader(new InputStreamReader(fin)); loadedString = buffRead.readLine(); fin.close(); } /** Catch the error if we can't open the file */ catch(IOException e) { System.err.println("CRITICAL: Unable to open text file!"); System.err.println("Exiting!"); System.exit(-1); } The one comment I had from him was that fin.close(); needed to be in a finally block, which I did not have at all. But I thought that the way I have created the try/catch it would have prevented an issue with the file not opening. Let me be clear on a few things: This is not for a current assignment (not trying to get someone to do my own work), I have already created my project and have been graded on it. I did not fully understand my Professor's reasoning myself. Finally, I do not have a lot of Java experience, so I was a little confused why my catch wasn't good enough.

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  • Dynamic control click event not firing properly

    - by Wil
    I'm creating a next/previous function for my repeater using pageddatasource. I added the link button control dynamically in my oninit using the following code. LinkButton lnkNext = new LinkButton(); lnkNext.Text = "Next"; lnkNext.Click += new EventHandler(NextPage); if (currentPage != objPagedDataSource.PageCount) { pnlMain.Controls.Add(lnkNext); } So in my initial page_load, the next link comes up fine. There are 5 pages in my objPagedDataSource. currentPage variable is 1. The "NextPage" event handler looks like this public void NextPage(object sender, EventArgs e) { if (HttpContext.Current.Request.Cookies["PageNum"] == null) { HttpCookie cookie = new HttpCookie("PageNum"); cookie.Value = "1"; } else { HttpCookie cookie = HttpContext.Current.Request.Cookies["PageNum"]; cookie.Value = (Convert.ToInt32(cookie.Value) + 1).ToString(); } this.BindRepeater(); } So I am incrementing the cookie I am using to track the page number and then rebinding the repeater. Here is the main issue. The first time I click Next, it works, it goes to Page 2 without any problems. When on Page 2, I click Next, it goes back to Page 1. Seems like the Next event is not wiring up properly. Not sure why, any ideas?

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  • Questions Regarding Handling of Received SMS

    - by Edwin
    Hi, i have managed to successfully write a little test app that can receive and send SMS, but got a couple of questions. (That's 'cos part of the code i copied from elsewhere and i would like to understand better). In my AndroidManifest as well as the sub-class of BroadcastReceiver, there is reference to the string literal "android.provider.Telephony.SMS_RECEIVED". However, i couldn't find any reference in the API that mentions this. Could someone point me to some reference that lists/explains these? As part of getting the message from the Intent, i did this: Object[] pdus = (Object[]) intent.getExtras().get("pdus"); Again this question is related to the use of hardcoded string literal. Where is the string "pdus" listed and described? Thanks in advance!

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  • Ruby Methods: return an usage string when insufficient arguments are given

    - by Shyam
    Hi, After creating a serious bunch of classes, with initialize methods, loading them in IRb requires to look back at the code. However, I think it should be easy enough to return a usage message, instead of: ArgumentError: wrong number of arguments (0 for 9) So I prefer to return a string with the human readable arguments, by example using "puts" or just a return of a string. Now I have seen the rescue keyword inside begin-end code, but I wonder how I could catch the ArgumentError when the initialize method is called. Thank you for your answers, feedback and comments!

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  • Correct Exceptions in C++

    - by Dr.Ackula
    I am just learning how to handle errors in my C++ code. I wrote this example that looks for a text file called some file, and if its not found will throw an exception. #include <iostream> #include <fstream> using namespace std; int main() { int array[90]; try { ifstream file; file.open("somefile.txt"); if(!file.good()) throw 56; } catch(int e) { cout<<"Error number "<<e<<endl; } return 0; } Now I have two questions. First I would like to know if I am using Exceptions correctly. Second, (assuming the first is true) what is the benefit to using them vs an If else statement?

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  • How to handle touch events on UI Controls

    - by Sreelatha
    Hi, I have a query related to Touch events on the UI controls. I have 4 controls on the screen ( UITextField, UISlider, UISwitch, UIButton ). If the user touches any of the control on the screen, I want to fire touchesBegan and touchesEnded events on those controls in which I would implement some code. Please let me know how to fire these events. Thanks in advance, Sreelatha.

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  • Handling large datasets with PHP/Drupal

    - by jo
    Hi all, I have a report page that deals with ~700k records from a database table. I can display this on a webpage using paging to break up the results. However, my export to PDF/CSV functions rely on processing the entire data set at once and I'm hitting my 256MB memory limit at around 250k rows. I don't feel comfortable increasing the memory limit and I haven't got the ability to use MySQL's save into outfile to just serve a pre-generated CSV. However, I can't really see a way of serving up large data sets with Drupal using something like: $form = array(); $table_headers = array(); $table_rows = array(); $data = db_query("a query to get the whole dataset"); while ($row = db_fetch_object($data)) { $table_rows[] = $row->some attribute; } $form['report'] = array('#value' => theme('table', $table_headers, $table_rows); return $form; Is there a way of getting around what is essentially appending to a giant array of arrays? At the moment I don't see how I can offer any meaningful report pages with Drupal due to this. Thanks

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  • errorPage directive works, but error-page in web.xml doesn't?

    - by danb
    I get jsp exceptions causing a forward to my error page when I put this at the top of my JSPs... <%@ page errorPage="/error.page" %> but when I try to do it globally with web.xml like so: <error-page> <exception-type>java.lang.Throwable</exception-type> <location>/error.page</location> </error-page> I just get a blank page... I've also tried putting /error.jsp in the location element.. but no love with that either.. I am triggering an exception with a jsp that just contains this: <%if(true)throw new RuntimeException("test exception");%> I do see the exception in the console from tomcat but I just can't get that error page to show without a directive on every jsp... am I missing something simple here?

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  • Flexible string handling in Visual Studio 2008 C++

    - by David
    I'm slowly starting to get the hang of the _T stuff in Visual Studio 2008 c++, but a few things still elude me. I can see the benefit of the flexibility, but if I can't get the basics soon, I think I'll go back to the standard way of doing this - much less confusing. The idea with the code below is that it scans the parameters for -d and then stores the text that follows that in the string variable fileDir. It also ignores any other parameters. Any help is appreciated. //Console application Parameters::Parameters(int argc, _TCHAR* argv[]) { _Tstring fileDir; // Is there some kind of _t variable to use here for a string? for (int i = 0; i < argc; i = i + 1) { if (_tccmp(argv[i], _T("-d")) == 0) // this appeared to accept anything starting with - { i = i + 1; fileDir = argv[i] } } _tprintf("Parameter value found: %s\n", fileDir); }

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  • Strange exception phenomenon in Windows 7

    - by Level 2
    I spot some interesting articles about exception handle in CodeProject http://www.codeproject.com/KB/cpp/seexception.aspx After reading, I decided to do some experiment. The first time I try to execute the following code char *p; p[0] = 0; The program died without question. But After several times when I executed the same problem binary code, it magically did fine. Even the following code is doing well. Any clue or explanation? char *p p[1000] = 'd'; cout<<p[1000]<<endl; My O/S is Windows 7 64bit and compiler is VS2008 rc1.

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  • What is a good "Error Checking" Pattern (Java)?

    - by Jack
    I'll explain what I mean by input error checking. Say you have a function doSomething(x). If the function completes successfully doSomething does something and returns nothing. However, if there are errors I'd like to be notified. That is what I mean by error checking. I'm looking for, in general, the best way to check for errors. I've thought of the following solutions, each with a potential problem. Flag error checking. If doSomething(x) completes successfully return null. Otherwise, it returns a boolean or an error string. Problem: Side effects. Throwing an exception. Throw an exception if doSomething(x) encounters an error. Problem: If you are performing error checking for parameters only, throwing an IllegalArgumentExceptionseems inappropriate. Validating input prior to function call. If the error checking is only meant for the parameters of the function, then you can call a validator function before calling the doSomething(x) function. Problem: What if a client of the class forgets to call the validator function before calling doSomething(x)? I often encounter this problem and any help or a point in the right direction would be much appreciated.

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  • Why does "return ERROR" only work with exceptions?

    - by ThreaT
    In the struts.xml I use: <result name="error">error</result> Then in my action I use: addActionError("ERROR RETURNED"); return ERROR; When I submit the form then it just goes to a blank page and does nothing. However, if I FORCE an exception to be thrown in the action then it goes to the error page and shows the ActionError message. So am I doing this wrong? If so, how should I tell struts to show an error page using "if statements" instead of relying solely on expensive try catches? EDIT 1: I'm using struts 2 version: 2.1.8.1 EDIT 2: For example, here is my action code that I'm using to test: String test = ""; int number = 0; try { if (number == 1) { System.out.println("number 1: " + number); test = SUCCESS; } else if (number == 2) { System.out.println("number 2: " + number); addActionError("ERROR RETURNED?"); addActionMessage("TESTTEST"); test = ERROR; } else if (number == 3) { System.out.println("number 3: " + number); addActionError("ERROR RETURNED?"); addActionMessage("TESTTEST"); test = INPUT; } else { System.out.println("number 4: " + number); test = LOGIN; } } catch (Exception e) { addActionError("ERROR RETURNED? " + e); } return test; And here is my JSP code: <s:form action="number_save" method="post"> <s:textfield name="number" label="Enter number" /> </s:form> <s:actionerror /> <s:fielderror /> <s:actionmessage /> EDIT 3: Here is a longer version of my struts.xml: <action name="number" method="numberCreate" class="NumberActionBean"> <result>number.jsp</result> </action> <action name="error"> <result>error.jsp</result> </action> <action name="number_save" method="numberSave" class="NumberActionBean"> <interceptor-ref name="defaultStack"></interceptor-ref> <result name="success" type="redirect">index</result> <result name="input" type="redirect">number</result> <result name="error">error</result> <result name="login" type="redirect">login</result> <result name="none">number</result> </action> EDIT 4: My error.jsp is simply a <s:actionerror /> tag with the general taglibs and html tags...

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  • Firing PropertyChanged event in a complex, nested type in WPF

    - by John
    Hey I have a question about the PropertyChanged vent firing in WPF whne it is used in a complex type. I have a class called DataStore and a list of Departments (an ObservableCollection), and each department again has a list of Products. Properties in the Product class that are changed also affect properties in the Department and DataStore class. How does each Product notify the Department it belongs to, and the DataStore (which is the mother class of all) that one or more of its properties have changed their values? Example: a product has a property NumberSoldToday and is bound. The Department has a property called TotalNumberOfProductsSold: public int TotalNumberOfProductsSold { get { int result = 0; foreach(Product p in this.products) result += p.NumberSoldToday; return result; } } And the data store has a property TotalProductsSold (for all departments): public int TotalProductsSold { get { int result = 0; foreach(Product p in this.deparments) result += p.TotalNumberOfProductsSold; return result; } } If all these properties are bound, and the innermost property changes, it must somehow notify that the value of the other 2 changed as well. How? The only way I can see this happening is to hook up the PropertyChanged event in each class. Th event must also fire when deleting, adding to the collection of products and deparments, respectively. Is there a better, more clever way to do this?

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  • Best practices for handling binary data in Ruby?

    - by StackedCrooked
    What are the best practices for reading and writing binary data in Ruby? In the code sample below I needed to send a binary file using over HTTP (as POST data): f = File.new("resp.der", "r") # binary file begin while true out.syswrite(f.sysread(1)) # out is an output stream (type IO) end rescue EOFError => err puts "Sent response." end While this code seems to do a good job, it probably isn't very idiomatic. How can I improve it?

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  • related to list and file handling?

    - by kaushik
    i have file with contents in list form such as [1,'ab','fgf','ssd'] [2,'eb','ghf','hhsd'] [3,'ag','rtf','ssfdd'] i want to read that file line by line using f.readline and assign thn to a list so as to use it is the prog as a list for using list properties tried like k=[ ] k=f.readline() print k[1] i xpected a result to show 2nd element in the list in first line but it showed the first bit and gave o/p as '1' how to get the xpected output.. please suggest

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  • Handling primary key duplicates in a data warehouse load

    - by Meff
    I'm currently building an ETL system to load a data warehouse from a transactional system. The grain of my fact table is the transaction level. In order to ensure I don't load duplicate rows I've put a primary key on the fact table, which is the transaction ID. I've encountered a problem with transactions being reversed - In the transactional database this is done via a status, which I pick up and I can work out if the transaction is being done, or rolled back so I can load a reversal row in the warehouse. However, the reversal row will have the same transaction ID and so I get a primary key violation. I've solved this for now by negating the primary key, so transaction ID 1 would be a payment, and transaction ID -1 (In the warehouse only) would be the reversal. I have considered an alternative of generating a BIT column, where 0 is normal and 1 is reversal, then making the PK the transaction ID and the BIT column. My question is, is this a good practice, and has anyone else encountered anything like this? For reference, this is a payment processing system, so values will not be modified, so there will only ever be transactions and reversals.

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  • Neural Network: Handling unavailable inputs

    - by Mike
    Hopefully the last NN question you'll get from me this weekend, but here goes :) Is there a way to handle an input that you "don't always know"... so it doesn't affect the weightings somehow? Soo... if I ask someone if they are male or female and they would not like to answer, is there a way to disregard this input? Perhaps by placing it squarely in the centre? (assuming 1,0 inputs at 0.5?) Thanks

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