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• Which tools to use and how to find file descriptors leaking from Glassfish?

  - by cclark

  We release new code to production every week and Glassfish hasn't had any problems. This weekend we had to move racks at our hosting provider. There were not any code changes (they just powered off, moved, re-racked and powered on) but we're on a new network infrastructure and suddenly we're leaking file descriptors like a sieve. So I'm guessing there is some sort of connection attempting to be made which now fails due to a network change. I'm running Glassfish v2ur2-b04/AS9.1_02 on RHEL4 with an embedded IMQ instance. After the move I started seeing: [#|2010-04-25T05:34:02.783+0000|SEVERE|sun-appserver9.1|javax.enterprise.system.container.web|_ThreadID=33;_ThreadName=SelectorThread-?4848;_RequestID=c4de6f6d-c1d6-416d-ac6e-49750b1a36ff;|WEB0756: Caught exception during HTTP processing. java.io.IOException: Too many open files at sun.nio.ch.ServerSocketChannelImpl.accept0(Native Method) ... [#|2010-04-25T05:34:03.327+0000|WARNING|sun-appserver9.1|javax.enterprise.system.stream.err|_ThreadID=34;_ThreadName=Timer-1;_RequestID=d27e1b94-d359-4d90-a6e3-c7ec49a0f383;|java.lang.NullPointerException at com.sun.jbi.management.system.AutoAdminTask.pollAutoDirectory(AutoAdminTask.java:1031) Using lsof I check the number of file descriptors and I see quite a few entries which look like: java 18510 root 8556u sock 0,4 1555182 can't identify protocol java 18510 root 8557u sock 0,4 1555320 can't identify protocol java 18510 root 8558u sock 0,4 1555736 can't identify protocol java 18510 root 8559u sock 0,4 1555883 can't identify protocol If I do a count of open file descriptors every minute I see it growing by 12 every minute. I have no idea what these sockets are. I've undeployed my application so there is only a plain Glassfish instance running and I still see it leaking 12 file descriptors a minute. So I think this leak is in Glassfish or potentially IMQ. What approach should I take to tracking down these sockets of unknown protocol? What tools can I use (or flags can I pass to lsof) to get more information about where to look? thanks, chuck

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• Problem in accessing Windows shared folder on Ubuntu using terminal

  - by vikramtheone

  Hi Guys, Description I have 2 systems with me, one running on Windows(Host) and one on Ubuntu, both on a LAN. On the Windows(Host) I develop software intended for the Linux system and because the Linux system has little external memory, my idea to overcome this is by making the project folder on the Host side a Shared Folder with full access and access it on Ubuntu over the network. To achieve this, I have installed Samba on Ubuntu, when I go to Places -> Network I can see the shared project folder and I simply mount it. A link appears on the desktop. Next, using Nautilus I open the link and I can access the contents of the shared folder. Problem Even though I mount the shared project folder, I don't see it appearing in the /media or the /mnt folder, as a result of this I don't know what path to use to access this folder, from the terminal. For example: When, I mounted my USB stick, as expected, a link for the device appears on the Desktop and I also see a folder in the media folder. So, similarly, a mounted shared folder should have appeared on the /mnt folder, too. Can anyone suggest what I should do now? There are many posts around, but no solid solution for this problem. Help!!! :) Vikram

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• Is my method for avoiding dynamic_cast<> faster than dynamic_cast<> itself ?

  - by ereOn

  Hi, I was answering a question a few minutes ago and it raised to me another one: In one of my projects, I do some network message parsing. The messages are in the form of: [1 byte message type][2 bytes payload length][x bytes payload] The format and content of the payload are determined by the message type. I have a class hierarchy, based on a common class Message. To instanciate my messages, i have a static parsing method which gives back a Message* depending on the message type byte. Something like: Message* parse(const char* frame) { // This is sample code, in real life I obviously check that the buffer // is not NULL, and the size, and so on. switch(frame[0]) { case 0x01: return new FooMessage(); case 0x02: return new BarMessage(); } // Throw an exception here because the mesage type is unknown. } I sometimes need to access the methods of the subclasses. Since my network message handling must be fast, I decived to avoid dynamic_cast<> and I added a method to the base Message class that gives back the message type. Depending on this return value, I use a static_cast<> to the right child type instead. I did this mainly because I was told once that dynamic_cast<> was slow. However, I don't know exactly what it really does and how slow it is, thus, my method might be as just as slow (or slower) but far more complicated. What do you guys think of this design ? Is it common ? Is it really faster than using dynamic_cast<> ? Any detailed explanation of what happen under the hood when one use dynamic_cast<> is welcome !

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• How does a client find the port number of a server?

  - by Jonathan

  Hello all, I am currently learning about basic networking in java. I have been playing around with the server and client relationship between two of my computers. However, I cannot figure out how distributed programs (say, a videogame), can not only find the 'host' computer, but also the port number on which the server is running in order to create a Socket between the two computers. The only way I really see to create a Socket is with an already known IP Address, and with a known port number. How do you search a LAN network for another computer (host) searching for clients? How do you determine what port the server is located on without 'pinging' all available ports for a response (which, I understand, is bad form... Something about 'server attack'...)? In such a situation as a video game, there can be any number of computers on the same network, and any number of them might be attempting to host, or otherwise running the application. Any other important information, or perhaps reference to a more detailed tutorial than the one I am using, regarding making connections on so very little information on the client side would be appreciated. Many thanks, Jonathan

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• how to update UI controls in cocoa application from background thread

  - by AmitSri

  following is .m code: #import "ThreadLabAppDelegate.h" @interface ThreadLabAppDelegate() - (void)processStart; - (void)processCompleted; @end @implementation ThreadLabAppDelegate @synthesize isProcessStarted; - (void)awakeFromNib { //Set levelindicator's maximum value [levelIndicator setMaxValue:1000]; } - (void)dealloc { //Never called while debugging ???? [super dealloc]; } - (IBAction)startProcess:(id)sender { //Set process flag to true self.isProcessStarted=YES; //Start Animation [spinIndicator startAnimation:nil]; //perform selector in background thread [self performSelectorInBackground:@selector(processStart) withObject:nil]; } - (IBAction)stopProcess:(id)sender { //Stop Animation [spinIndicator stopAnimation:nil]; //set process flag to false self.isProcessStarted=NO; } - (void)processStart { int counter = 0; while (counter != 1000) { NSLog(@"Counter : %d",counter); //Sleep background thread to reduce CPU usage [NSThread sleepForTimeInterval:0.01]; //set the level indicator value to showing progress [levelIndicator setIntValue:counter]; //increment counter counter++; } //Notify main thread for process completed [self performSelectorOnMainThread:@selector(processCompleted) withObject:nil waitUntilDone:NO]; } - (void)processCompleted { //Stop Animation [spinIndicator stopAnimation:nil]; //set process flag to false self.isProcessStarted=NO; } @end I need to clear following things as per the above code. How to interrupt/cancel processStart while loop from UI control? I also need to show the counter value in main UI, which i suppose to do with performSelectorOnMainThread and passing argument. Just want to know, is there anyother way to do that? When my app started it is showing 1 thread in Activity Monitor, but when i started the processStart() in background thread its creating two new thread,which makes the total 3 thread until or unless loop get finished.After completing the loop i can see 2 threads. So, my understanding is that, 2 thread created when i called performSelectorInBackground, but what about the thrid thread, from where it got created? What if thread counts get increases on every call of selector.How to control that or my implementation is bad for such kind of requirements? Thanks

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• 64-bit Alternative for Microsoft Jet

  - by David Robison

  Microsoft has chosen to not release a 64-bit version of Jet, their database driver for Access. Does anyone know of a good alternative? Here are the specific features that Jet supports that I need: Multiple users can connect to database over a network. Users can use Windows Explorer to copy the database while it is open without risking corruption. Access currently does this with enough reliability for what my customers need. Works well in C++ without requiring .Net. Alternatives I've considered that I do not think could work (though my understanding could be incorrect): SQLite: If multiple users connect to the database over a network, it will become corrupted. Firebird: Copying a database that is in use can corrupt the original database. SQL Server: Files in use are locked and cannot be copied. VistaDB: This appears to be .Net specific. Compile in 32-bit and use WOW64: There is another dependency that requires us to compile in 64-bit, even though we don't use any 64-bit functionality.

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• How to receive Email in JEE application

  - by Hank

  Obviously it's not so difficult to send out emails from a JEE application via JavaMail. What I am interested in is the best pattern to receive emails (notification bounces, mostly)? I am not interested in IMAP/POP3-based approaches (polling the inbox) - my application shall react to inbound emails. One approach I could think of would be Keep existing MTA (postfix on linux in my case) - ops team already knows how to configure / operate it For every mail that arrives, spawn a Java app that receives the data and sends it off via JMS. I could do this via an entry in /etc/aliases like myuser: "|/path/to/javahelper" with javahelper calling the Java app, passing STDIN along. MDB (part of JEE application) receives JMS message, parses it, detects bounce message and acts accordingly. Another approach could be Open a listening network socket on port 25 on the JEE application container. Associate a SessionBean with the socket. Bean is part of JEE application and can parse/detect bounces/handle the messages directly. Keep existing MTA as inbound relay, do all its security/spam filtering, but forward emails to myuser (that pass the filter) to the JEE application container, port 25. The first approach I have done before (albeit in a different language/setup). From a performance and (perceived) cleanliness point of view, I think the second approach is better, but it would require me to provide a proper SMTP transport implementation. Also, I don't know if it's at all possible to connect a network socket with a bean... What is your recommendation? Do you have details about the second approach?

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• How can i get rid of 'ORA-01489: result of string concatenation is too long' in this query?

  - by core_pro

  this query gets the dominating sets in a network. so for example given a network A<----->B B<----->C B<----->D C<----->E D<----->C D<----->E F<----->E it returns B,E B,F A,E but it doesn't work for large data because i'm using string methods in my result. i have been trying to remove the string methods and return a view or something but to no avail With t as (select 'A' as per1, 'B' as per2 from dual union all select 'B','C' from dual union all select 'B','D' from dual union all select 'C','B' from dual union all select 'C','E' from dual union all select 'D','C' from dual union all select 'D','E' from dual union all select 'E','C' from dual union all select 'E','D' from dual union all select 'F','E' from dual) ,t2 as (select distinct least(per1, per2) as per1, greatest(per1, per2) as per2 from t union select distinct greatest(per1, per2) as per1, least(per1, per2) as per1 from t) ,t3 as (select per1, per2, row_number() over (partition by per1 order by per2) as rn from t2) ,people as (select per, row_number() over (order by per) rn from (select distinct per1 as per from t union select distinct per2 from t) ) ,comb as (select sys_connect_by_path(per,',')||',' as p from people connect by rn > prior rn ) ,find as (select p, per2, count(*) over (partition by p) as cnt from ( select distinct comb.p, t3.per2 from comb, t3 where instr(comb.p, ','||t3.per1||',') > 0 or instr(comb.p, ','||t3.per2||',') > 0 ) ) ,rnk as (select p, rank() over (order by length(p)) as rnk from find where cnt = (select count(*) from people) order by rnk ) select distinct trim(',' from p) as p from rnk where rnk.rnk = 1`

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• Upload using python script takes very long on one laptop as compared to another

  - by Engr Am

  I have a python 2.7 code which uses STORBINARY function for uploading files to an ftp server and RETRBINARY for downloading from this server. However, the issue is the upload is taking a very long time on three laptops from different brands as compared to a Dell laptop. The strange part is when I manually upload any file, it takes the same time on all the systems. The manual upload rate and upload rate with the python script is the same on the Dell Laptop. However, on every other brand of laptop (I have tried with IBM, Toshiba, Fujitsu-Siemens) the python script has a very low upload rate than the manual attempt. Also, on all these other laptops, the upload rate using the python script is the same (1Mbit/s) while the manual upload rate is approx. 8 Mbit/s. I have tried to vary the filesize for the upload to no avail. TCP Optimizer improved the download rate on all the systems but had no effect on the upload rate. Download rate using this script on all the systems is fine and same as the manual download rate. I have checked the server and it has more than 90% free space. The network connection is the same for all the laptops, and I try uploading only with one laptop at a time. All the laptops have almost the same system configurations, same operating system and approximately the same free drive space. If anything the Dell laptop is a little less in terms of processing power and RAM than 2 of the others, but I suppose this has no effect as I have checked many times to see how much was the CPU usage and network usage during these uploads and downloads, and I am sure that no other virus or program has been eating up my bandwidth. Here is the code ('ftp' and 'file_path' are inputs to the function): path,filename=os.path.split(file_path) filesize=os.path.getsize(file_path) deffilesize=(filesize/1024)/1024 f = open(file_path, "rb") upstart = time.clock() print ftp.storbinary("STOR "+filename, f) upende = time.clock()-upstart outname="Upload " f.close() return upende, deffilesize, outname

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• UIActivityIndicatorView in a class without a view

  - by Structurer

  Hi I have defined a class that does a lengthy task and I call it from several other classes. Now I want to show an Activity Indicator while this task is doing it's thing, and then remove it once it's done. Since this is just a boring background task, this class doesn't have a view, and I guess that is where I run into my problem. I can't get this thing to show. This is what I have done in my class: UIActivityIndicatorView *activityIndicator = [[UIActivityIndicatorView alloc] initWithFrame:CGRectMake(0.0f, 0.0f, 32.0f, 32.0f)]; [activityIndicator setCenter:CGPointMake(160.0f, 208.0f)]; activityIndicator.activityIndicatorViewStyle = UIActivityIndicatorViewStyleWhite; UIView *contentView = [[UIView alloc]initWithFrame:[[UIScreen mainScreen] applicationFrame]]; [contentView addSubview:activityIndicator]; [activityIndicator startAnimating]; // Do the class lengthy task that takes several seconds..... [contentView release]; [activityIndicator release]; I guess I do something wrong when I get the contentView, but how should I get it properly? Thanks for any advices...

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• Analyzing Web Application Speed

  - by Amy

  I'm a bit confused because the logical/programmer brain in me says that if all things are constant, the speed of a function must be constant. I am working on a PHP web application with jqGrid as a front end for showing the data. I am testing on my personal computer, so network traffic does not apply. I make an HTTP request to a PHP function, it returns the data, and then jqGrid renders it. What has me befuddled is that sometimes, Firebug reports that this is taking 300-600 milliseconds sometimes, and sometimes, it's taking 3.68 seconds. I can run the request over and over again, with very radically different response times. The query is the same. The number of users on the system is the same. No network latency. Same code. I'm not running other applications on the computer while testing. I could understand query caching improving performance on subsequent requests, but the speed is just fluctuating wildly with no rhyme or reason. So, my question is, what else can cause such variability in the response time? How can I determine what's doing it? More importantly, is there any way to get things more consistent?

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• ASP .NET page runs slow in production

  - by Brandi

  I have created an ASP .NET page that works flawlessly and quickly from Visual Studio. It does a very large database read from a database on our network to load a gridview inside of an update panel. It displays progress in an Ajax modalpopupextender. Of course I don't expect it to be instant what with the large db reads, but it takes on the order of seconds, not on the order of minutes. This is all working great until I put it up on the server - it is very, VERY slow when I access it via the internet - takes several minutes to load the database information into the gridview. I'm baffled why it would not perform the exact same as it had from Visual Studio. (It is in release mode and I have taken off the debug flag) I have since been trying things like eliminating unneeded update panels and throwing out the ajax tool. Nothing has made it any faster on production. It is not the database as far as I know, since it has been consistently fast from my computer (from visual studio) and consistently slow from the server. I am wondering, where do I look next? Has anyone else had this problem before? Could this be caused by update panels or Ajax modalpopupextenders in different parts of the application? Why would the live behaviour differ so much from the localhost behaviour? Both the server with the ASP .NET page and the server with the database are servers on our network. I'm using Visual Studio 2008. Thank you in advance for any insight or advice.

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• C++ return a "NULL" object if search result not found

  - by aduric

  I'm pretty new to C++ so I tend to design with a lot of Java-isms while I'm learning. Anyway, in Java, if I had class with a 'search' method that would return an object T from a Collection< T that matched a specific parameter, I would return that object and if the object was not found in the collection, I would return a NULL. Then in my calling function I would just check if(T != NULL) { ... } In C++, I'm finding out that I can't return a NULL if the object doesn't exist. I just want to return an 'indicator' of type T that notifies the calling function that no object has been found. I don't want to throw an exception because it's not really an exceptional circumstance. class Node { .... Attr& getAttribute(const string& attribute_name) const { //search collection //if found at i return attributes[i]; //if not found return NULL; } private: vector<Attr> attributes; }

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• Sending Email over VPN SmtpException net_io_connectionclosed

  - by Holy Christ

  I am sending an email from a WPF application. When sending as a domain user on the network, the emails sends as expected. However, when I attempt to send email over a VPN connection, I get the following exception: Exception: System.Net.Mail.SmtpException: Failure sending mail. --- System.IO.IOException: Unable to read data from the transport connection: net_io_connectionclosed. at System.Net.Mail.SmtpReplyReaderFactory.ProcessRead(Byte[] buffer, Int32 offset, Int32 read, Boolean readLine) at System.Net.Mail.SmtpReplyReaderFactory.ReadLines(SmtpReplyReader caller, Boolean oneLine) at System.Net.Mail.SmtpReplyReaderFactory.ReadLine(SmtpReplyReader caller) at System.Net.Mail.SmtpConnection.GetConnection(String host, Int32 port) at System.Net.Mail.SmtpTransport.GetConnection(String host, Int32 port) at System.Net.Mail.SmtpClient.GetConnection() at System.Net.Mail.SmtpClient.Send(MailMessage message) I have tried using impersonation as well as setting the Credentials on the SmtpClient. Neither seem to work: using (new ImpersonateUser("myUser", "MYDOMAIN", "myPass")) { var client = new SmtpClient("myhost.com"); client.UseDefaultCredentials = true; client.Credentials = new NetworkCredential("myUser", "myPass", "MYDOMAIN"); client.Send(mailMessage); } I've also tried using Wireshark to view the message over the wire, but I don't know enough about SMTP to know what I'm looking for. One other variable is that the machine I'm using on the VPN is Vista Business and the machine on the network is Win7. I don't think it's related, but then I wouldn't be asking if I knew the issue! :) Any ideas?

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• Alternative or succesor to GDBM

  - by Anon Guy

  We a have a GDBM key-value database as the backend to a load-balanced web-facing application that is in implemented in C++. The data served by the application has grown very large, so our admins have moved the GDBM files from "local" storage (on the webservers, or very close by) to a large, shared, remote, NFS-mounted filesystem. This has affected performance. Our performance tests (in a test environment) show page load times jumping from hundreds of milliseconds (for local disk) to several seconds (over NFS, local network), and sometimes getting as high as 30 seconds. I believe a large part of the problem is that the application makes lots of random reads from the GDBM files, and that these are slow over NFS, and this will be even worse in production (where the front-end and back-end have even more network hardware between them) and as our database gets even bigger. While this is not a critical application, I would like to improve performance, and have some resources available, including the application developer time and Unix admins. My main constraint is time only have the resources for a few weeks. As I see it, my options are: Improve NFS performance by tuning parameters. My instinct is we wont get much out of this, but I have been wrong before, and I don't really know very much about NFS tuning. Move to a different key-value database, such as memcachedb or Tokyo Cabinet. Replace NFS with some other protocol (iSCSI has been mentioned, but i am not familiar with it). How should I approach this problem?

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• Approaches to replace cursor in pure AS3 / Flare project?

  - by peteorpeter

  Hi there good lookin, I've got a pure AS3 (no Flex) project that uses Flare to display and interact with a data visualization. I just implemented some panning behavior, so you can click and drag the visualization around, and now I'd like to give the user a visual indicator that this is possible, by switching the arrow cursor with a nice grabby-looking hand icon. The user can click and drag at any time except when the mouse is over a clickable node (at which time the cursor swaps to a pointer - this behavior is already in place). So... 1) Do I need to create my own custom bitmap/sprite or is there a palette of built-in cursors I can use? (I'm not using Flex.) 2) Is there a way to simply replace the default arrow with the pan cursor project-wide, or do I need to attach the swapping to mouse events on display objects? Can I use the stage object to make this behavior apply everywhere? 3) How do I perform the swap? Do I use the Cursor object directly or do I need to get involved with the CursorManager? Any guidance, pseudo-code, or words of wisdom is greatly appreciated!

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• Setup SVN/LAMP/Test Server/ on linux, where to start?

  - by John Isaacks

  I have a ubuntu machine I have setup. I installed apache2 and php5 on it. I can access the web server from other machines on the network via http://linux-server. I have subversion installed on it. I also have vsftpd installed on it so I can ftp to it from another computer on the network. Myself and other users currently use dreamweaver to checkin-checkout files directly from our live site to make changes. I want the connect to the linux server from pc. make the changes on the test server until ready and then pushed to the live site. I want to use subversion also into this workflow as well. but not sure what the best workflow is or how to set this up. I have no experience with linux, svn, or even using a test server, the checkin/out we are currently doing is the way I have always done it. I have hit many snags already just getting what I have setup because of my lack of knowledge in the area. Dreamweaver 5 has integration with subversion but I can't figure out how to get it to work. I want to setup and create the best workflow possible. I dont expect anyone to be able to give me an answer that will enlighten me enough to know everthing I need to know to do what I want to do (altough if possible that would be great) instead I am looking for maybe a knowledge path like answer. Like a general outline of what I need to do accompanied with links to learn how to do it. like read this book to learn linux, then read this article to learn svn, etc., then you should know what to do. I would be happy just getting it all setup, but I would like to know what I am actually doing while setting it up too.

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• Django: Applying Calculations To A Query Set

  - by TheLizardKing

  I have a QuerySet that I wish to pass to a generic view for pagination: links = Link.objects.annotate(votes=Count('vote')).order_by('-created')[:300] This is my "hot" page which lists my 300 latest submissions (10 pages of 30 links each). I want to now sort this QuerySet by an algorithm that HackerNews uses: (p - 1) / (t + 2)^1.5 p = votes minus submitter's initial vote t = age of submission in hours Now because applying this algorithm over the entire database would be pretty costly I am content with just the last 300 submissions. My site is unlikely to be the next digg/reddit so while scalability is a plus it is required. My question is now how do I iterate over my QuerySet and sort it by the above algorithm? For more information, here are my applicable models: class Link(models.Model): category = models.ForeignKey(Category, blank=False, default=1) user = models.ForeignKey(User) created = models.DateTimeField(auto_now_add=True) modified = models.DateTimeField(auto_now=True) url = models.URLField(max_length=1024, unique=True, verify_exists=True) name = models.CharField(max_length=512) def __unicode__(self): return u'%s (%s)' % (self.name, self.url) class Vote(models.Model): link = models.ForeignKey(Link) user = models.ForeignKey(User) created = models.DateTimeField(auto_now_add=True) def __unicode__(self): return u'%s vote for %s' % (self.user, self.link) Notes: I don't have "downvotes" so just the presence of a Vote row is an indicator of a vote or a particular link by a particular user.

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• How Would a Newborn Baby Learn Web Programming?

  - by Mugatu

  Hello all, I chose that title because I equate my knowledge of web programming and web development with that of a newborn. Here's the shortest version of my story and what I'm looking to do: A friend and I have been coming up with website ideas for a couple years, mostly just jotting them down whenever we come up with a good, useful idea when browsing the web. For the past 6 months we've hired a couple different programmers to make a couple of the sites for us, but have been disappointed with how it's gone. Been too slow and too many miscommunications for our liking. So like the saying goes if you want something done right do it yourself, we're going to do it ourselves. I know nothing about programming, I've never written a line of code in my life. I consider myself very good with math and about as logical as you can get, but I have zero real-life programming knowledge. The sites we want to make are all pretty 'Web 2.0'ish', meaning user-generated content, commenting on posts, pages that change on the fly, etc. So here are some of my questions for anyone who's been there before: Is there a language you'd recommend learning first? Something that is a good indicator how most other languages work? What web programming languages do you recommend learning first based on popularity both now and the future. I don't want to learn a language that's going to be outdated by the time I'm an expert at it. Any specific books you'd recommend? Any general advice you'd give to someone literally starting at square zero for coding who plans on being in it for the long haul? Thanks in advance for the help

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• How to find an embedded platform?

  - by gmagana

  I am new to the locating hardware side of embedded programming and so after being completely overwhelmed with all the choices out there (pc104, custom boards, a zillion option for each board, volume discounts, devel kits, ahhh!!) I am asking here for some direction. Basically, I must find a new motherboard and (most likely) re-implement the program logic. Rewriting this in C/C++/Java/C#/Pascal/BASIC is not a problem for me. so my real problem is finding the hardware. This motherboard will have several other devices attached to it. Here is a summary of what I need to do: Required: 2 RS232 serial ports (one used all the time for primary UI, the second one not continuous) 1 modem (9600+ baud ok) [Modem will be in simultaneous use with only one of the serial port devices, so interrupt sharing with one serial port is OK, but not both] Minimum permanent/long term storage: Whatever O/S requires + 1 MB (executable) + 512 KB (Data files) RAM: Minimal, whatever the O/S requires plus maybe 1MB for executable. Nice to have: USB port(s) Ethernet network port Wireless network Implementation languages (any O/S I will adapt to): First choice Java/C# (Mono ok) Second choice is C/Pascal Third is BASIC Ok, given all this, I am having a lot of trouble finding hardware that will support this that is low in cost. Every manufacturer site I visit has a lot of options, and it's difficult to see if their offering will even satisfy my must-have requirements (for example they sometimes list 3 "serial ports", but it appears that only one of the three is RS232, for example, and don't mention what the other two are). The #1 constraint is cost, #2 is size. Can anyone help me with this? This little task has left me thinking I should have gone for EE and not CS :-). EDIT: A bit of background: This is a system currently in production, but the original programmer passed away, and the current hardware manufacturer cannot find hardware to run the (currently) DOS system, so I need to reimplement this in a modern platform. I can only change the programming and the motherboard hardware.

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• How can someone with no experience learn how to program?

  - by Mugatu

  A friend and I have been coming up with website ideas for a couple years, mostly just jotting them down whenever we come up with a good, useful idea when browsing the web. For the past 6 months we've hired a couple different programmers to make a couple of the sites for us, but have been disappointed with how it's gone. Been too slow and too many miscommunications for our liking. So like the saying goes if you want something done right do it yourself, we're going to do it ourselves. I know nothing about programming, I've never written a line of code in my life. I consider myself very good with math and about as logical as you can get, but I have zero real-life programming knowledge. The sites we want to make are all pretty 'Web 2.0'ish', meaning user-generated content, commenting on posts, pages that change on the fly, etc. So here are some of my questions for anyone who's been there before: Is there a language you'd recommend learning first? Something that is a good indicator how most other languages work? What web programming languages do you recommend learning first based on popularity both now and the future. I don't want to learn a language that's going to be outdated by the time I'm an expert at it. Any specific books you'd recommend? Any general advice you'd give to someone literally starting at square zero for coding who plans on being in it for the long haul?

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• How do I connect to SQL Server with VB?

  - by Wayne Werner

  Hi, I'm trying to connect to a SQL server from VB. The SQL server is across the network uses my windows login for authentication. I can access the server using the following python code: import odbc conn = odbc.odbc('SignInspection') c = conn.cursor() c.execute("SELECT * FROM list_domain") c.fetchone() This code works fine, returning the first result of the SELECT. However, I've been trying to use the SqlClient.SqlConnection in VB, and it fails to connect. I've tried several different connection strings but this is the current code: Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Dim conn As New SqlClient.SqlConnection conn.ConnectionString = "data source=signinspection;initial catalog=signinspection;integrated security=SSPI" Try conn.Open() MessageBox.Show("Sweet Success") 'Insert some code here, woo Catch ex As Exception MessageBox.Show("Failed to connect to data source.") MessageBox.Show(ex.ToString()) Finally conn.Close() End Try End Sub It fails miserably, and it gives me an error that says "A network-related or instance-specific error occurred... (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server) I'm fairly certain it's my connection string, but nothing I've found has given me any solid examples (server=mySQLServer is not a solid example) of what I need to use. Thanks! -Wayne

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• LDAP/AD Integrated Group/Membership Management Package suitable for embedding in an application

  - by Ernest

  In several web applications, it is often necessary to define groups of users for purposes of membership as well as role management. For example, in one of our applications we would like to user a group of "Network Engineers" and another group that consists of "Managers" of such Network Engineers. The information we need is contact details of members of each group. So far, we have written our own tools to allow the administrator of the application to add/delete/move groups and their memberships and either store them in a XML file or a database. Increasingly, companies already have the groups we want defined in LDAP/AD, so it would be best to create a pointer in our application to the correspoding group in LDAP. Although there are a number of LDAP libraries and LDAP browsers available and we could code this and provide a web front end to get a list of available groups and their members, we are wondering if there is already a "component framework" available that would readily provide this LDAP browsing functionality that we could just embed this into our application. Something between a library and a full LDAP browser product ? (To clarify, the use case is for an admin of our web application to create a locally relevant group name and then map it to an exiting LDAP group. To enable this in the UI, we would like to present a way for the admin to browse available groups in the company LDAP server, view their membership, and select the LDAP group they would like to map to the locally relevant group name. In a second step, we would then synchronize the members of that LDAP group and their contact details to a store in our application ) Appreciate any pointers.

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• Should I close sockets from both ends?

  - by Roman

  I have the following problem. My client program monitor for availability of server in the local network (using Bonjour, but it does not rally mater). As soon as a server is "noticed" by the client application, the client tries to create a socket: Socket(serverIP,serverPort);. At some point the client can loose the server (Bonjour says that server is not visible in the network anymore). So, the client decide to close the socket, because it is not valid anymore. At some moment the server appears again. So, the client tries to create a new socket associated with this server. But! The server can refuse to create this socket since it (server) has already a socket associated with the client IP and client port. It happens because the socket was closed by the client, not by the server. Can it happen? And if it is the case, how this problem can be solved? Well, I understand that it is unlikely that the client will try to connect to the server from the same port (client port), since client selects its ports randomly. But it still can happen (just by chance). Right?

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• Ruby On Rails with HTML5 offline apps - Firefox does not cache the application.manifest but Safari does

  - by hoitomt

  I'm working off of this Railscast tutorial: episode 247 I’m up to this point in the tutorial: added the rack-offline gem, added the application.manifest route, and added a reference to the manifest in the html tag. Right before it starts talking about problems with caching. Safari works as intended – When the server is running the page is served. From the server logs I can see that Safari is making a single request to the server every time for the items page. When I turn off the server the page displays as well, even after shutting down the browser and restarting. It appears to be pulling from the application.manifest (cache manifest). Firefox does not work as intended – When accessing the page for the first time, Firefox lets me know that the web page wants to store something locally, I allow. After clicking on allow, Firefox makes 5 requests to the server for the page (from the server log). The hash is different in every request. Is it is possible that the changing hash is triggering Firefox to keep trying to get the new manifest until it reaches some maximum (5 attempts)? Then, after the server is stopped, Firefox will not show the page at all. It looks like it isn’t caching the application.manifest. Firefox also gives you a way to see what sites are storing stuff locally by going to Tools/Options/Advanced/Network (Firefox/Preferences/Advanced/Network on Apple). I see localhost there but the size is 0 bytes. So for some reason, Firefox is not downloading my application.manifest along with the files

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