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• Why calling Process.killProcess(Process.myPid()) is a bad idea?

  - by Tal Kanel

  I've read some posts saying using this method is "not good", shouldn't been use, it's not the right way to "close" the application and it's not how android works... I understand and accept the fact that Android OS knows better then me when it's the right time to terminate the process, but I didn't heard yet a good explanation why it's wrong using the killProcess() method?. after all - it's part of the android API... what I do know is that calling this method while other threads doing in potential an important work (operations on files, writing to DB, HTTP requests, running services..) can be terminated in the middle, and it's clearly not good. also I know I can benefit from the fact that "re-open" the application will be faster, cause the system maybe still "holds" in memory state from last time been used, and killProcess() prevents that. beside this reason, in assumption I don't have such operations, and I don't care my application will load from scratch each run, there are other reasons why not using the killProcess() method? I know about finish() method to close an Activity, so don't write me about that please.. finish() is only for Activity. not to all application, and I think I know exactly why and when to use it... and another thing - I'm developing also games with the Unity3D framework, and exporting the project to android. when I decompiled the generated apk, I was very suprised to find out that the java source code created from unity - implementing Unity's - Application.quit() method, with Process.killProcess(Process.myPid()). Application.quit() is suppose to be the right way to close game according to Unity3d guides (is it really?? maybe I'm wrong, and missed something), so how it happens that the Unity's framework developers which doing a very good work as it seems implemented this in native android to killProcess()? anyway - I wish to have a "list of reasons" why not using the killProcess() method, so please write down your answer - if you have something interesting to say about that. TIA

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• FileNotFoundException when reading .xml file to parse

  - by thechiman

  I'm writing a program in Java where I read in data from an XML file and parse it. The file is imported into a folder named "Resources" in the src directory of my project. I'm using Eclipse. When I run the program, I get the following error: java.io.FileNotFoundException: /Users/thechiman/Dropbox/introcs/PSU SOC Crawler/resources/majors_xml_db.xml (No such file or directory) at java.io.FileInputStream.open(Native Method) at java.io.FileInputStream.<init>(FileInputStream.java:106) at java.io.FileInputStream.<init>(FileInputStream.java:66) ... The relevant code is here: private void parseXML() { //Get a factory DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance(); try { //Use factory to get a new DocumentBuilder DocumentBuilder db = dbf.newDocumentBuilder(); //Parse the XML file, get DOM representation dom = db.parse("resources/majors_xml_db.xml"); } catch(ParserConfigurationException pce) { pce.printStackTrace(); } catch(SAXException se) { se.printStackTrace(); } catch(IOException ioe) { ioe.printStackTrace(); } } I do not understand why I'm getting the FileNotFoundException when the file is there. Thanks for the help.

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• Looking for a smarter way to convert a Python list to a GList?

  - by Kingdom of Fish

  I'm really new to C - Python interaction and am currently writing a small app in C which will read a file (using Python to parse it) and then using the parsed information to execute small Python snippets. At the moment I'm feeling very much like I'm reinventing wheels, for example this function: typedef gpointer (list_func)(PyObject *obj); GList *pylist_to_glist(list_func func, PyObject *pylist) { GList *result = NULL; if (func == NULL) { fprintf(stderr, "No function definied for coverting PyObject.\n"); } else if (PyList_Check(pylist)) { PyObject *pIter = PyObject_GetIter(pylist); PyObject *pItem; while ((pItem = PyIter_Next(pIter))) { gpointer obj = func(pItem); if (obj != NULL) result = g_list_append(result, obj); else fprintf(stderr, "Could not convert PyObject to C object.\n"); Py_DECREF(pItem); } Py_DECREF(pIter); } return result; } I would really like to do this in a easier/smarter way less prone to memory leaks and errors. All comments and suggestions are appreciated.

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• Getting text between quotes using regular expression

  - by Camsoft

  I'm having some issues with a regular expression I'm creating. I need a regex to match against the following examples and then sub match on the first quoted string: Input strings ("Lorem ipsum dolor sit amet, consectetur adipiscing elit.") ('Lorem ipsum dolor sit amet, consectetur adipiscing elit. ') ('Lorem ipsum dolor sit amet, consectetur adipiscing elit. ', 'arg1', "arg2") Must sub match Lorem ipsum dolor sit amet, consectetur adipiscing elit. Regex so far: \((["'])([^"']+)\1,?.*\) The regex does a sub match on the text between the first set of quotes and returns the sub match displayed above. This is almost working perfectly, but the problem I have is that if the quoted string contains quotes in the text the sub match stops at the first instance, see below: Failing input strings ("Lorem ipsum dolor \"sit\" amet, consectetur adipiscing elit.") Only sub matches: Lorem ipsum dolor ("Lorem ipsum dolor 'sit' amet, consectetur adipiscing elit.") The entire match fails. Notes The input strings are actually php code function calls. I'm writing a script that will scan .php source files for a specific function and grab the text from the first parameter.

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• Python: Seeing all files in Hex.

  - by Recursion

  I am writing a python script which looks at common computer files and examines them for similar bytes, words, double word's. Though I need/want to see the files in Hex, ande cannot really seem to get python to open a simple file in python. I have tried codecs.open with hex as the encoding, but when I operate on the file descriptor it always spits back File "main.py", line 41, in <module> main() File "main.py", line 38, in main process_file(sys.argv[1]) File "main.py", line 27, in process_file seeker(line.rstrip("\n")) File "main.py", line 15, in seeker for unit in f.read(2): File "/usr/lib/python2.6/codecs.py", line 666, in read return self.reader.read(size) File "/usr/lib/python2.6/codecs.py", line 472, in read newchars, decodedbytes = self.decode(data, self.errors) File "/usr/lib/python2.6/encodings/hex_codec.py", line 50, in decode return hex_decode(input,errors) File "/usr/lib/python2.6/encodings/hex_codec.py", line 42, in hex_decode output = binascii.a2b_hex(input) TypeError: Non-hexadecimal digit found def seeker(_file): f = codecs.open(_file, "rb", "hex") for LINE in f.read(): print LINE f.close() I really just want to see files, and operate on them as if it was in a hex editor like xxd. Also is it possible to read a file in increments of maybe a word at a time. No this is not homework.

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• Java Robot key activity seems to stop working while certain software is running

  - by Mike Turley

  I'm writing a Java application to automate character actions in an online game overnight (specifically, it catches fish in Final Fantasy XI). The app makes heavy use of java's Robot class both for emulating user keyboard input and for detecting color changes on certain parts of the screen. It also uses multithreading and a swing GUI. The application seems to work perfectly when I test it without the game running, just using screenshots to trigger the apps responses into notepad. But for some reason, when I actually launch FFXI and start the program, all of my keyboard and mouse manipulations just stop working altogether. The program is still running, and the Robot class is still able to read pixel colors. But Robot.keyPress, Robot.keyRelease, Robot.mouseMove, Robot.mousePress and Robot.mouseRelease all do nothing. It's the strangest thing-- to test it, I wrote a simple loop that just keeps typing letters, and focused notepad. I'd then start the game, refocus notepad, and it would do nothing. Then I'd exit the game, and it'd start working again immediately. Has anyone else come across something like this, where specific software will stop certain functions of java from working? Also, to make this more interesting-- Last year I wrote a very similar program using the same classes and programming techniques to automate healing a party in the game as they fight. Last year, this program worked perfectly. After running into these problems I dug up that old program, ran it without making any changes, and found that it too was having the same problems. The only differences between now and when it was working: I was running Windows Vista and now I'm running Windows 7, and several new Java versions as well as FFXI versions have been released. What the hell is going on? (if anyone needs to see my source code, email me at [email protected]. I'm trying to keep it to myself.)

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• Is there a more easy way to create a WCF/OData Data Service Query Provider?

  - by routeNpingme

  I have a simple little data model resembling the following: InventoryContext { IEnumerable<Computer> GetComputers() IEnumerable<Printer> GetPrinters() } Computer { public string ComputerName { get; set; } public string Location { get; set; } } Printer { public string PrinterName { get; set; } public string Location { get; set; } } The results come from a non-SQL source, so this data does not come from Entity Framework connected up to a database. Now I want to expose the data through a WCF OData service. The only way I've found to do that thus far is creating my own Data Service Query Provider, per this blog tutorial: http://blogs.msdn.com/alexj/archive/2010/01/04/creating-a-data-service-provider-part-1-intro.aspx ... which is great, but seems like a pretty involved undertaking. The code for the provider would be 4 times longer than my whole data model to generate all of the resource sets and property definitions. Is there something like a generic provider in between Entity Framework and writing your own data source from zero? Maybe some way to build an object data source or something, so that the magical WCF unicorns can pick up my data and ride off into the sunset without having to explicitly code the provider?

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• Implementing crossover in genetic programming

  - by Name

  Hi, I'm writing a genetic programming (GP) system (in C but that's a minor detail). I've read a lot of the literature (Koza, Poli, Langdon, Banzhaf, Brameier, et al) but there are some implementation details I've never seen explained. For example: I'm using a steady state population rather than a generational approach, primarily to use all of the computer's memory rather than reserve half for the interim population. Q1. In GP, as opposed to GA, when you perform crossover you select two parents but do you create one child or two, or is that a free choice you have? Q2. In steady state GP, as opposed to a generational system, what members of the population do the children created by crossover replace? This is what I haven't seen discussed. Is it the two parents, or is it two other, randomly-selected members? I can understand if it's the latter, and that you might use negative tournament selection to choose members to replace, but would that not create premature convergence? (After a crossover event the population contains the two original parents plus two children of those parents, and two other random members get removed. Elitism is inherent.) Q3. Is there a Web forum or mailing list focused on GP? Oddly I haven't found one. Yahoo's GP group is used almost exclusively for announcements, the Poli/Langdon Field Guide forum is almost silent, and GP discussions on general/game programming sites like gamedev.net are very basic. Thanks for any help you can provide!

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• How to preprocess text to do OCR error correction

  - by eaglefarm

  Here is what I'm trying to accomplish: I need to get a several large text files from a computer that is not networked and has no other output except a printer. I tried printing the text, then scanning the printout with OCR to recover the text on another computer but the OCR gets lots of errors (1 vs l, o vs 0, O vs D, etc). To solve this I am thinking of writing a program to process (annotate?) the text file, before printing it, so that the errors can be corrected from the text output of the OCR program. For example, for 1 (number one) vs l (letter L), I could change the text like this: sample inserting \nnn after characters that are frequently wrong in the OCR results: sampl\108e Then I can write another program to examine the file, looking for \nnn and check the character before the \nnn (where nnn is the ascii code in decimal) and fix it if necessary. Of course the program will have to recognize that the \nnn may have errors too but at least it knows that the nnn are digits and can easily correct them. I think I would add a CRC on each line so that any line that isn't corrected perfectly can be flagged as having a problem. Has anyone done anything like this? If there is an existing way of doing this I'd rather not reinvent the wheel. Or any suggestions for annotation format that would help solve this problem would be helpful too.

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• Cannot install XML::LibXML module on Windows

  - by Deepak Konidena

  I am trying to use XPath to extract some HTML tags and data and for that I need to use XML::LibXML module. I tried installing it from CPAN shell but it doesn't install. I followed the instructions from CPAN site about the installation, that we need to install libxml2, iconv and zlib wrappers before installing XML::LibXML and it didn't work out. Also, if there is any other simpler module that gets my task done, please let me know. The task at hand: I am searching for a specific <dd> tag on a html page which is really big ( around 5000 - 10000) <dd> and <dt> tags. So, I am writing a script which matches the content within <dd> tag and fetches the content within the corresponding (next) <dt> tag. I wish i could i have been a little more clearer. Any help is greatly appreciated.

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• Common JNDI resources in Tomcat

  - by Lehane

  Hi, I’m running a couple of servlet applications in Tomcat (5.5). All of the servlets use a common factory resource that is shared out using JNDI. At the moment, I can get everything working by including the factory resource as a GlobalNamingResource in the /conf/server.xml file, and then having each servlet’s META-INF/context.xml file include a ResourceLink to the resource. Snippets from the XML files are included below. NOTE: I’m not that familiar with tomcat, so I’m not saying that this is a good configuration!!! However, I now want to be able install these servlets into multiple tomcat instances automatically using an RPM. The RPM will firstly copy the WARs to the webapps directory, and the jars for the factory into the common/lib directory (which is fine). But it will also need to make sure that the factory resource is included as a resource for all of the servlets. What is the best way add the resource globally? I’m not too keen on writing a script that goes into the server.xml file and adds in the resource that way. Is there any way for me to add in multiple server.xml files so that I can write a new server-app.xml file and it will concatenate my settings to server.xml? Or, better still to add this JNDI resource to all the servlets without using server.xml at all? p.s. Restarting the server will not be an issue, so I don’t mind if the changes don’t get picked up automatically. Thanks Snippet from server.xml <!-- Global JNDI resources --> <GlobalNamingResources> <Resource name="bean/MyFactory" auth="Container" type="com.somewhere.Connection" factory="com.somewhere.MyFactory"/> </GlobalNamingResources> The entire servlet’s META-INF/context.xml file <?xml version="1.0" encoding="UTF-8"?> <Context> <ResourceLink global="bean/MyFactory" name="bean/MyFactory" type="com.somewhere.MyFactory"/> </Context>

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• Can this method to convert a name to proper case be improved?

  - by Kelsey

  I am writing a basic function to convert millions of names (one time batch process) from their current form, which is all upper case, to a proper mixed case. I came up with the following so far: public string ConvertToProperNameCase(string input) { TextInfo textInfo = new CultureInfo("en-US", false).TextInfo; char[] chars = textInfo.ToTitleCase(input.ToLower()).ToCharArray(); for (int i = 0; i + 1 < chars.Length; i++) { if ((chars[i].Equals('\'')) || (chars[i].Equals('-'))) { chars[i + 1] = Char.ToUpper(chars[i + 1]); } } return new string(chars);; } It works in most cases such as: JOHN SMITH - John Smith SMITH, JOHN T - Smith, John T JOHN O'BRIAN - John O'Brian JOHN DOE-SMITH - John Doe-Smith There are some edge cases that do no work like: JASON MCDONALD - Jason Mcdonald (Correct: Jason McDonald) OSCAR DE LA HOYA - Oscar De La Hoya (Correct: Oscar de la Hoya) MARIE DIFRANCO - Marie Difranco (Correct: Marie DiFranco) These are not captured and I am not sure if I can handle all these odd edge cases. Can anyone think of anything I could change or add to capture more edge case? I am sure there are tons of edge cases I am not even thinking of as well. All casing should following North American conventions too meaning that if certain countries expect a specific capitalization format, and that differs from the North American format, then the North American format takes precedence.

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• SQL database problems with addressbook table design

  - by Sebastian Hoitz

  Hello! I am writing a addressbook module for my software right now. I have the database set up so far that it supports a very flexible address-book configuration. I can create n-entries for every type I want. Type means here data like 'email', 'address', 'telephone' etc. I have a table named 'contact_profiles'. This only has two columns: id Primary key date_created DATETIME And then there is a table called contact_attributes. This one is a little more complex: id PK #profile (Foreign key to contact_profiles.id) type VARCHAR describing the type of the entry (name, email, phone, fax, website, ...) I should probably change this to a SET later. value Text (containing the value for the attribute). I can now link to these profiles, for example from my user's table. But from here I run into problems. At the moment I would have to create a JOIN for each value that I want to retrieve. Is there a possibility to somehow create a View, that gives me a result with the type's as columns? So right now I would get something like #profile type value 1 email [email protected] 1 name Sebastian Hoitz 1 website domain.tld But it would be nice to get a result like this: #profile email name website 1 [email protected] Sebastian Hoitz domain.tld The reason I do not want to create the table layout like this initially is, that there might always be things to add and I want to be able to have multiple attributes of the same type. So do you know if there is any possibility to convert this dynamically? If you need a better description please let me know. Thank you!

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• WCF Custom Delegation/Authentication without Kerberos

  - by MichaelGG

  I'm building a simple WCF service, probably exposed via HTTPS, using NTLM security. Since not all users are going to be capable of using the service directly, we're writing a simple web front-end for the service. Users will auth with HTML to the web front-end. What we want is a way to delegate the user of the web site all the way to the WCF service. I understand Kerberos delegation can do this, but that's not available to us. What I want to do is make the web front-end account a specially trusted account, so that if a request hits the WCF service authenticated as "DOMAIN\WebApp", we read a WCF message header containing the real identity, then switch the principal to that and continue as normal. Is there any "simple" way of achieving this? Should I give up entirely on this idea, and instead make users "sign-in" to the WCF app and then do complete custom auth? The WCF extensibility and security options seem so vast, I'd like to get a heads up on which path to start heading down.

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• Why do Unicode characters show up properly in database, but as ? when printed in Java via Hibernate?

  - by lupefiasco

  I'm writing a webapp, and interfacing with MySQL using Hibernate 3.5. Using "?????? ?????????" as my test string, I can input the string and see that it is properly persisted into the database. However, when I later pull the value out of the database and print to the console as a String, I see "?????? ?????????". If I use new OutputStreamWriter(System.out,"UTF-8"); then I get "„Éá„Çp„ÇØ„Éà„ÉÉ„Éó ·Éò·Éú·Éí·Éö·Éò·É°·É£·É†·Éò"". Why don't I see the original string? These are my hibernate.cfg.xml settings: <property name="hibernate.connection.useUnicode"> true </property> <property name="hibernate.connection.characterEncoding"> UTF-8 </property> <property name="hibernate.connection.charSet"> UTF-8 </property> and this is my database connection string: hibernate.connection.url = jdbc:mysql://localhost/mydatabase?autoReconnect=true&amp;useUnicode=true&amp;characterEncoding=UTF-8

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• Simple, fast SQL queries for flat files.

  - by plinehan

  Does anyone know of any tools to provide simple, fast queries of flat files using a SQL-like declarative query language? I'd rather not pay the overhead of loading the file into a DB since the input data is typically thrown out almost immediately after the query is run. Consider the data file, "animals.txt": dog 15 cat 20 dog 10 cat 30 dog 5 cat 40 Suppose I want to extract the highest value for each unique animal. I would like to write something like: cat animals.txt | foo "select $1, max(convert($2 using decimal)) group by $1" I can get nearly the same result using sort: cat animals.txt | sort -t " " -k1,1 -k2,2nr And I can always drop into awk from there, but this all feels a bit awkward (couldn't resist) when a SQL-like language would seem to solve the problem so cleanly. I've considered writing a wrapper for SQLite that would automatically create a table based on the input data, and I've looked into using Hive in single-processor mode, but I can't help but feel this problem has been solved before. Am I missing something? Is this functionality already implemented by another standard tool? Halp!

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• PostgreSQL: Rolling back a transaction within a plpgsql function?

  - by jamieb

  Coming from the MS SQL world, I tend to make heavy use of stored procedures. I'm currently writing an application uses a lot of PostgreSQL plpgsql functions. What I'd like to do is rollback all INSERTS/UPDATES contained within a particular function if I get an exception at any point within it. I was originally under the impression that each function is wrapped in it's own transaction and that an exception would automatically rollback everything. However, that doesn't seem to be the case. I'm wondering if I ought to be using savepoints in combination with exception handling instead? But I don't really understand the difference between a transaction and a savepoint to know if this is the best approach. Any advice please? CREATE OR REPLACE FUNCTION do_something( _an_input_var int ) RETURNS bool AS $$ DECLARE _a_variable int; BEGIN INSERT INTO tableA (col1, col2, col3) VALUES (0, 1, 2); INSERT INTO tableB (col1, col2, col3); VALUES (0, 1, 'whoops! not an integer'); -- The exception will cause the function to bomb, but the values -- inserted into "tableA" are not rolled back. RETURN True; END; $$ LANGUAGE plpgsql;

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• Sending Email through Gmail

  - by persistence

  I am writing a program that send an email through GMail but I have serious Operation timeout error. What is the likely cause. class Mailer { MailMessage ms; SmtpClient Sc; public Mailer() { Sc = new SmtpClient("smtp.gmail.com"); //Sc.Credentials = CredentialCache.DefaultNetworkCredentials; Sc.EnableSsl = true; Sc.Port =465; Sc.Timeout = 900000000; Sc.DeliveryMethod = SmtpDeliveryMethod.Network; Sc.UseDefaultCredentials = false; Sc.Credentials = new NetworkCredential("uid", "mypss"); } public void MailTodaysBirthdays(List<Celebrant> TodaysCelebrant) { int i = TodaysCelebrant.Count(); foreach (Celebrant cs in TodaysCelebrant) { //if (IsEmail(cs.EmailAddress.ToString().Trim())) //{ ms = new MailMessage(); ms.To.Add(cs.EmailAddress); ms.From = new MailAddress("uid","Developers",System.Text.Encoding.UTF8); ms.Subject = "Happy Birthday "; String EmailBody = "Happy Birthday " + cs.FirstName; ms.Body = EmailBody; ms.Priority = MailPriority.High; try { Sc.Send(ms); } catch (Exception ex) { Sc.Send(ms); BirthdayServices.LogEvent(ex.Message.ToString(),EventLogEntryType.Error); } //} } } }

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• Write a compiler for a language that looks ahead and multiple files?

  - by acidzombie24

  In my language I can use a class variable in my method when the definition appears below the method. It can also call methods below my method and etc. There are no 'headers'. Take this C# example. class A { public void callMethods() { print(); B b; b.notYetSeen(); public void print() { Console.Write("v = {0}", v); } int v=9; } class B { public void notYetSeen() { Console.Write("notYetSeen()\n"); } } How should I compile that? what i was thinking is: pass1: convert everything to an AST pass2: go through all classes and build a list of define classes/variable/etc pass3: go through code and check if there's any errors such as undefined variable, wrong use etc and create my output But it seems like for this to work I have to do pass 1 and 2 for ALL files before doing pass3. Also it feels like a lot of work to do until I find a syntax error (other than the obvious that can be done at parse time such as forgetting to close a brace or writing 0xLETTERS instead of a hex value). My gut says there is some other way. Note: I am using bison/flex to generate my compiler.

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• Smack API giving error while logging into Tigase Server setup locally

  - by Ameya Phadke

  Hi, I am currently developing android XMPP client to communicate with the Tigase server setup locally.Before starting development on Android I am writing a simple java code on PC to test connectivity with XMPP server.My XMPP domain is my pc name "mwbn43-1" and administrator username and passwords are admin and tigase respectively. Following is the snippet of the code I am using class Test { public static void main(String args[])throws Exception { System.setProperty("smack.debugEnabled", "true"); XMPPConnection.DEBUG_ENABLED = true; ConnectionConfiguration config = new ConnectionConfiguration("mwbn43-1", 5222); config.setCompressionEnabled(true); config.setSASLAuthenticationEnabled(true); XMPPConnection con = new XMPPConnection(config); // Connect to the server con.connect(); con.login("admin", "tigase"); Chat chat = con.getChatManager().createChat("aaphadke@mwbn43-1", new MessageListener() { public void processMessage(Chat chat, Message message) { // Print out any messages we get back to standard out. System.out.println("Received message: " + message); } }); try { chat.sendMessage("Hi!"); } catch (XMPPException e) { System.out.println("Error Delivering block"); } String host = con.getHost(); String user = con.getUser(); String id = con.getConnectionID(); int port = con.getPort(); boolean i = false; i = con.isConnected(); if (i) System.out.println("Connected to host " + host + " via port " + port + " connection id is " + id); System.out.println("User is " + user); con.disconnect(); } } When I run this code I get following error Exception in thread "main" Resource binding not offered by server: at org.jivesoftware.smack.SASLAuthentication.bindResourceAndEstablishSession(SASLAuthenticatio n.java:416) at org.jivesoftware.smack.SASLAuthentication.authenticate(SASLAuthentication.java:331) at org.jivesoftware.smack.XMPPConnection.login(XMPPConnection.java:395) at org.jivesoftware.smack.XMPPConnection.login(XMPPConnection.java:349) at Test.main(Test.java:26) I found this articles on the same problem but no concrete solution here Could anyone please tell me the solution for this problem.I checked the XMPPConnection.java file in the Smack API and it looks the same as given in the link solution. Thanks, Ameya

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• Linux System Programming

  - by AJ

  I wanted to get into systems programming for linux and wanted to know how to approach that and where to begin. I come from a web development background (Python, PHP) but I also know some C and C++. Essentially, I would like to know: Which language(s) to learn and pursue (I think mainly C and C++)? How/Where to learn those languages specific to Systems Programming? Books, websites, blogs, tutorials etc. Any other good places where I can start this from basics? Any good libraries to begin with? What environment setup (or approx.) do I need? Assuming linux has to be there but I have a linux box which I rarely log into using GUI (always use SSH). Is GUI a lot more helpful or VI editor is enough? (Please let me know if this part of the question should go to serverfault.com) PS: Just to clarify, by systems programming I mean things like writing device drivers, System tools, write native applications which are not present on Linux platform but are on others, play with linux kernel etc.

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• python: how to design a container with elements that must reference their container

  - by Luke404

  (the title is admittedly not that great. Please forgive my English, this is the best I could think of) I'm writing a python script that will manage email domains and their accounts, and I'm also a newby at OOP design. My two (related?) issues are: the Domain class must do special work to add and remove accounts, like adding/removing them to the underlying implementation how to manage operations on accounts that must go through their container To solve the former issue I'd add a factory method to the Domain class that'll build an Account instance in that domain, and a 'remove' (anti-factory?) method to handle deletions. For the latter this seems to me "anti-oop" since what would logically be an operation on an Account (eg, change password) must always reference the containing Domain. Seems to me that I must add to the Account a reference back to the Domain and use that to get data (like the domain name) or call methods on the Domain class. Code example (element uses data from the container) that manages an underlying Vpopmail system: class Account: def __init__(self, name, password, domain): self.name = name self.password = password self.domain = domain def set_password(self, password): os.system('vpasswd %s@%s %s' % (self.name, self.domain.name, password) self.password = password class Domain: def __init__(self, domain_name): self.name = domain_name self.accounts = {} def create_account(self, name, password): os.system('vadduser %s@%s %s' % (name, self.name, password)) account = Account(name, password, self) self.accounts[name] = account def delete_account(self, name): os.system('vdeluser %s@%s' % (name, self.name)) del self.accounts[name] another option would be for Account.set_password to call a Domain method that would do the actual work - sounds equally ugly to me. Also note the duplication of data (account name also as dict key), it sounds logical (account names are "primary key" inside a domain) but accounts need to know their own name.

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• Socket errors of 10048 on the client? Possible causes?

  - by Earlz

  Hello, I'm writing a custom TCP server and client and on doing a ton of requests (60,000 to be exact) I begin to get this socket error of 10048, which should mean "the address is already in use." The error keeps happening unless I pause the process for like 2 or 3 minutes and then begin it again, and then it begins to bring up the same error a short while after restarting it. If I pause the client process and restart the server process, I still get the same error on the client. So it is a complete client side problem. This does not make sense though, this error only usually occurs when binding and this error happens on the client and not the server. What could be the possible reasons for it? A small excerpt of my initialization: TcpClient client = new TcpClient(); client.Connect("XXXXX -- some ip", 25000); client.NoDelay = true; NetworkStream clientStream = client.GetStream(); Also, everything else seems to be working fine(including the amount of time it takes to send back and forth) and this works perfectly when using 127.0.0.1 but when putting it on another LAN computer I begin to get the 10048 error. Is there something wrong with how I initialize it? What else could cause this error on the client side?

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• How to get forkpty to handle redirection and other bash-isms?

  - by Jeremy Friesner

  Hi all, I've got a GUI C++ program that takes a shell command from the user, calls forkpty() and execvp() to execute that command in a child process, while the parent (GUI) process reads the child process's stdout/stderr output and displays it in the GUI. This all works nicely (under Linux and MacOS/X). For example, if the user enters "ls -l /foo", the GUI will display the contents of the /foo folder. However, bash niceties like output redirection aren't handled. For example, if the user enters "echo bar /foo/bar.txt", the child process will output the text "bar /foo/bar.txt", instead of writing the text "bar" to the file "/foo/bar.txt". Presumably this is because execvp() is running the executable command "echo" directly, instead of running /bin/bash and handing it the user's command to massage/preprocess. My question is, what is the correct child process invocation to use, in order to make the system behave exactly as if the user had typed in his string at the bash prompt? I tried wrapping the user's command with a /bin/bash invocation, like this: /bin/bash -c the_string_the_user_entered, but that didn't seem to work. Any hints?

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• Perl XML SAX parser emulating XML::Simple record for record

  - by DVK

  Short Q summary: I am looking a fast XML parser (most likely a wrapper around some standard SAX parser) which will produce per-record data structure 100% identical to those produced by XML::Simple. Details: We have a large code infrastructure which depends on processing records one-by-one and expects the record to be a data structure in a format produced by XML::Simple since it always used XML::Simple since early Jurassic era. An example simple XML is: <root> <rec><f1>v1</f1><f2>v2</f2></rec> <rec><f1>v1b</f1><f2>v2b</f2></rec> <rec><f1>v1c</f1><f2>v2c</f2></rec> </root> And example rough code is: sub process_record { my ($obj, $record_hash) = @_; # do_stuff } my $records = XML::Simple->XMLin(@args)->{root}; foreach my $record (@$records) { $obj->process_record($record) }; As everyone knows XML::Simple is, well, simple. And more importantly, it is very slow and a memory hog - due to being a DOM parser and needing to build/store 100% of data in memory. So, it's not the best tool for parsing an XML file consisting of large amount of small records record-by-record. However, re-writing the entire code (which consist of large amount of "process_record"-like methods) to work with standard SAX parser seems like an big task not worth the resources, even at the cost of living with XML::Simple. What I'm looking for is an existing module which will probably be based on a SAX parser (or anything fast with small memory footprint) which can be used to produce $record hashrefs one by one based on the XML pictured above that can be passed to $obj->process_record($record) and be 100% identical to what XML::Simple's hashrefs would have been.

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