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• How can I force the server socket to re-accept a request from a client?

  - by Roman

  For those who does not want to read a long question here is a short version: A server has an opened socket for a client. The server gets a request to open a socket from the same client-IP and client-port. I want to fore the server not to refuse such a request but to close the old socket and open a new one. How can I do ti? And here is a long (original) question: I have the following situation. There is an established connection between a server and client. Then an external software (Bonjour) says to my client the it does not see the server in the local network. Well, client does nothing about that because of the following reasons: If Bonjour does not see the server it does not necessarily means that client cannot see the server. Even if the client trusts the Bonjour and close the socket it does not improve the situation ("to have no open socket" is worser that "to have a potentially bad socket"). So, client do nothing if server becomes invisible to Bonjour. But than the server re-appears in the Bonjour and Bonjour notify the client about that. In this situation the following situations are possible: The server reappears on a new IP address. So, the client needs to open a new socket to be able to communicate with the server. The server reappears on the old IP address. In this case we have two subcases: 2.1. The server was restarted (switched off and then switched on). So, it does not remember the old socket (which is still used by the client). So, client needs to close the old socket and open a new one (on the same server-IP address and the same server-port). 2.2. We had a temporal network problem and the server was running the whole time. So, the old socket is still available for the use. In this case the client does not really need to close the old socket and reopen a new one. But to simplify my life I decide to close and reopen the socket on the client side in any case (in spite on the fact that it is not really needed in the last described situation). But I can have problems with that solution. If I close the socket on the client side and than try to reopen a socket from the same client-IP and client-port, server will not accept the call for a new socket. The server will think that such a socket already exists. Can I write the server in such a way, that it does not refuse such calls. For example, if it (the server) sees that a client send a request for a socket from the same client-IP and client-port, it (server) close the available socket, associated with this client-IP and client-port and than it reopens a new socket.

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• JavaScript (via Greasemonkey) failing to set "title" attributes on <a> tags

  - by rjray

  I have the following (fairly) simple JavaScript snippet that I have wired into Greasemonkey. It goes through a page, looks for <a> tags whose href points to tinyurl.com, and adds a "title" attribute that identifies the true destination of the link. Much of the important code comes from an older (unsupported) Greasemonkey script that quits working when the inner component that held the XPath implementation changed. My script: (function() { var providers = new Array(); providers['tinyurl.com'] = function(link, fragment) { // This is mostly taken from the (broken due to XPath component // issues) tinyurl_popup_preview script. link.title = "Loading..."; GM_xmlhttpRequest({ method: 'GET', url: 'http://preview.tinyurl.com/' + fragment, onload: function(res) { var re = res.responseText.match("<blockquote><b>(.+)</b></blockquote>"); if (re) { link.title = re[1].replace(/\<br \/\>/g, "").replace(/&amp;/g, "&"); } else { link.title = "Parsing failed..."; } }, onerror: function() { link.title = "Connection failed..."; } }); }; var uriPattern = /(tinyurl\.com)\/([a-zA-Z0-9]+)/; var aTags = document.getElementsByTagName("a"); for (i = 0; i < aTags.length; i++) { var data = aTags[i].href.match(uriPattern); if (data != null && data.length > 1 && data[2] != "preview") { var source = data[1]; var fragment = data[2]; var link = aTags[i]; aTags[i].addEventListener("mouseover", function() { if (link.title == "") { (providers[source])(link, fragment); } }, false); } } })(); (The reason the "providers" associative array is set up the way it is, is so that I can expand this to cover other URL-shortening services as well.) I have verified that all the various branches of code are being reached correctly, in cases where the link being examined does and does not match the pattern. What isn't happening, is any change to the "title" attribute of the anchor tags. I've watched this via Firebug, thrown alert() calls in left and right, and it just never changes. In a previous iteration all expressions of the form: link.title = "..."; had originally been: link.setAttribute("title", "..."); That didn't work, either. I'm no newbie to JavaScript OR Greasemonkey, but this one has me stumped!

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• Force deletion of slot in boost::signals2

  - by villintehaspam

  Hi! I have found that boost::signals2 uses sort of a lazy deletion of connected slots, which makes it difficult to use connections as something that manages lifetimes of objects. I am looking for a way to force slots to be deleted directly when disconnected. Any ideas on how to work around the problem by designing my code differently are also appreciated! This is my scenario: I have a Command class responsible for doing something that takes time asynchronously, looking something like this (simplified): class ActualWorker { public: boost::signals2<void ()> OnWorkComplete; }; class Command : boost::enable_shared_from_this<Command> { public: ... void Execute() { m_WorkerConnection = m_MyWorker.OnWorkDone.connect(boost::bind(&Command::Handle_OnWorkComplete, shared_from_this()); // launch asynchronous work here and return } boost::signals2<void ()> OnComplete; private: void Handle_OnWorkComplete() { // get a shared_ptr to ourselves to make sure that we live through // this function but don't keep ourselves alive if an exception occurs. shared_ptr<Command> me = shared_from_this(); // Disconnect from the signal, ideally deleting the slot object m_WorkerConnection.disconnect(); OnComplete(); // the shared_ptr now goes out of scope, ideally deleting this } ActualWorker m_MyWorker; boost::signals2::connection m_WorkerConnection; }; The class is invoked about like this: ... boost::shared_ptr<Command> cmd(new Command); cmd->OnComplete.connect( foo ); cmd->Execute(); // now go do something else, forget all about the cmd variable etcetera. the Command class keeps itself alive by getting a shared_ptr to itself which is bound to the ActualWorker signal using boost::bind. When the worker completes, the handler in Command is invoked. Now, since I would like the Command object to be destroyed, I disconnect from the signal as can be seen in the code above. The problem is that the actual slot object is not deleted when disconnected, it is only marked as invalid and then deleted at a later time. This in turn appears to depend on the signal to fire again, which it doesn't do in my case, leading to the slot never expiring. The boost::bind object thus never goes out of scope, holding a shared_ptr to my object that will never get deleted. I can work around this by binding using the this pointer instead of a shared_ptr and then keeping my object alive using a member shared_ptr which I then release in the handler function, but it kind of makes the design feel a bit overcomplicated. Is there a way to force signals2 to delete the slot when disconnecting? Or is there something else I could do to simplify the design? Any comments are appreciated!

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• Is order of parameters for database Command object really important?

  - by nawfal

  I was debugging a database operation code and I found that proper UPDATE was never happening though the code never failed as such. This is the code: condb.Open(); OleDbCommand dbcom = new OleDbCommand("UPDATE Word SET word=?,sentence=?,mp3=? WHERE id=? AND exercise_id=?", condb); dbcom.Parameters.AddWithValue("id", wd.ID); dbcom.Parameters.AddWithValue("exercise_id", wd.ExID); dbcom.Parameters.AddWithValue("word", wd.Name); dbcom.Parameters.AddWithValue("sentence", wd.Sentence); dbcom.Parameters.AddWithValue("mp3", wd.Mp3); But after some tweaking this worked: condb.Open(); OleDbCommand dbcom = new OleDbCommand("UPDATE Word SET word=?,sentence=?,mp3=? WHERE id=? AND exercise_id=?", condb); dbcom.Parameters.AddWithValue("word", wd.Name); dbcom.Parameters.AddWithValue("sentence", wd.Sentence); dbcom.Parameters.AddWithValue("mp3", wd.Mp3); dbcom.Parameters.AddWithValue("id", wd.ID); dbcom.Parameters.AddWithValue("exercise_id", wd.ExID); Why is it so important that the parameters in WHERE clause has to be given the last in case of OleDb connection? Having worked with MySQL previously, I could (and usually do) write parameters of WHERE clause first because that's more logical to me. Is parameter order important when querying database in general? Some performance concern or something? Is there a specific order to be maintained in case of other databases like DB2, Sqlite etc? Update: I got rid of ? and included proper names with and without @. The order is really important. In both cases only when WHERE clause parameters was mentioned last, actual update happened. To make matter worse, in complex queries, its hard to know ourselves which order is Access expecting, and in all situations where order is changed, the query doesnt do its intended duty with no warning/error!!

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• Command Not working in separate thread in J2me.

  - by RishiPatel

  I am creating a bluetooth application. I created a simple midlet with a exit command and i create a thread for finding the service and discovering the device. While doing so it displays a animated screen on which i added the parent commandListener for exit command. After successful connection both user is represented with greetings(Current screen calls the parent Display method setCurrent for displaying itself). This screen also have CommandListener set to the parent. Now i want to add few more commands. I Implemented the CommandLIstener Interface in this class, added few commands but the commands are not working. I dont whats wen wrong. I am giving u Code snippets to fully describle my issue : - package name Imports here public class MyMidlet extends MIDlet implements CommandListener { public CommandListener theListener; public Display theDisplay; public Command exitCommand; public MyMidlet() { // Retrieve the display for this MIDlet //Create the initial screen } public void startApp() throws MIDletStateChangeException { } public void pauseApp() { } public void destroyApp(boolean unconditional) { } public void commandAction(Command c, Displayable d) { // Determine if the exit command was selected if (c == exitCommand) { //End application here notifyDestroyed(); } else { //Start the new thread here } } } Now here is the code for the class which is invoked by the above midlet in a separate thread; package here; imports here public class MyService implements Runnable, CommandListener { private MyMidlet parent; private StreamConnection conn; private OutputStream output; private InputStream input; public Command sendCommand; private TextField messageToSend Form form; public BChatService(boolean isServer, BChatMidlet parent) { //some stuff here this.parent = parent; } public void run() { //functino for showing animation here try { input = conn.openInputStream(); output = conn.openOutputStream(); } catch (IOException e) { displayError("IO Error", "An error occurred while opening " + "the input and output streams" + "(IOException: " + e.getMessage() + ")"); try { conn.close(); } catch (Exception ex) { } return; } // Create the Form here when service is discoverd and greets the users Command sendCommand = new Command("Send", Command.ITEM, 2); exitCommand = new Command("Exit", Command.EXIT, 1); form.addCommand(exitCommand); form.addCommand(sendCommand); parent.theDisplay.setCurrent(form); form.setCommandListener(this); public void commandAction(Command c, Displayable d) { if (c == exitCommand) { // End the game parent.destroyApp(true); parent.notifyDestroyed(); } if(c == sendCommand) { form.append("SOme text here"); } } } When i select the Send command, the string doesnt append in form neither exit command works. What can be the possible cause for it?? I need to implement this functionality...Is there any other way to achieve this??

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• Getting this error while reading excel

  - by Lalit

  I have code string conn = @"Provider=Microsoft.ACE.OLEDB.12.0;DSN=Excel Files;DBQ=" + strSheetPath + @";DriverId=1046;FIL=excel 12.0;MaxBufferSize=2048;PageTimeout=5;"; //string conn = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + strSheetPath +";Extended Properties=Excel 12.0 Xml;HDR=YES;IMEX=1"; string destinationConnectionString = ConfigurationManager.ConnectionStrings["KGD6DBConnectionString"].ConnectionString; string query = "Select * From [Sheet1$]"; using (var myConnection = new OleDbConnection(conn)) using (var destinationConnection = new SqlConnection(destinationConnectionString)) using (var bulkCopy = new SqlBulkCopy(destinationConnection)) { //Map first column in source to second column in sql table (skipping the ID column). //Excel schema[CompanyName,Phone] Table schema[ShipperID, CompanyName, Phone] bulkCopy.ColumnMappings.Add(0, 1); bulkCopy.ColumnMappings.Add(1, 2); bulkCopy.ColumnMappings.Add(2, 3); bulkCopy.ColumnMappings.Add(3, 4); bulkCopy.ColumnMappings.Add(4, 5); bulkCopy.ColumnMappings.Add(5, 6); bulkCopy.ColumnMappings.Add(6, 7); bulkCopy.ColumnMappings.Add(7, 8); bulkCopy.ColumnMappings.Add(8, 9); bulkCopy.ColumnMappings.Add(9, 10); bulkCopy.ColumnMappings.Add(10, 11); bulkCopy.ColumnMappings.Add(11, 12); bulkCopy.ColumnMappings.Add(12, 13); bulkCopy.ColumnMappings.Add(13, 14); bulkCopy.ColumnMappings.Add(14, 15); bulkCopy.ColumnMappings.Add(15, 16); bulkCopy.ColumnMappings.Add(16, 17); bulkCopy.ColumnMappings.Add(17, 18); bulkCopy.ColumnMappings.Add(18, 19); bulkCopy.ColumnMappings.Add(19, 20); bulkCopy.ColumnMappings.Add(20, 21); bulkCopy.ColumnMappings.Add(21, 22); bulkCopy.ColumnMappings.Add(22, 23); bulkCopy.ColumnMappings.Add(23, 24); bulkCopy.DestinationTableName = "dbo.sampleInventory"; using (var myCommand = new OleDbCommand(query, myConnection)) { myConnection.Open(); destinationConnection.Open(); var myReader = myCommand.ExecuteReader(); while (myReader.Read()) { bulkCopy.WriteToServer(myReader); } } } return (new DataTable()); getting error on connection opening line. Error: Could not find installable ISAM.

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• Binding on a port with netpipes/netcat

  - by mindas

  I am trying to write a simple bash script that is listening on a port and responding with a trivial HTTP response. My specific issue is that I am not sure if the port is available and in case of bind failure I fall back to next port until bind succeeds. So far to me the easiest way to achieve this was something like: for (( i=$PORT_BASE; i < $(($PORT_BASE+$PORT_RANGE)); i++ )) do if [ $DEBUG -eq 1 ] ; then echo trying to bind on $i fi /usr/bin/faucet $i --out --daemon echo test 2>/dev/null if [ $? -eq 0 ] ; then #success? port=$i if [ $DEBUG -eq 1 ] ; then echo "bound on port $port" fi break fi done Here I am using faucet from netpipes Ubuntu package. The problem with this is that if I simply print "test" to the output, curl complains about non-standard HTTP response (error code 18). That's fair enough as I don't print HTTP-compatible response. If I replace echo test with echo -ne "HTTP/1.0 200 OK\r\n\r\ntest", curl still complains: user@server:$ faucet 10020 --out --daemon echo -ne "HTTP/1.0 200 OK\r\n\r\ntest" ... user@client:$ curl ip.of.the.server:10020 curl: (56) Failure when receiving data from the peer I think the problem lies in how faucet is printing the response and handling the connection. For example if I do the server side in netcat, curl works fine: user@server:$ echo -ne "HTTP/1.0 200 OK\r\n\r\ntest\r\n" | nc -l 10020 ... user@client:$ curl ip.of.the.server:10020 test user@client:$ I would be more than happy to replace faucet with netcat in my main script, but the problem is that I want to spawn independent server process to be able to run client from the same base shell. faucet has a very handy --daemon parameter as it forks to background and I can use $? (exit status code) to check if bind succeeded. If I was to use netcat for a similar purpose, I would have to fork it using & and $? would not work. Does anybody know why faucet isn't responding correctly in this particular case and/or can suggest a solution to this problem. I am not married neither to faucet nor netcat but would like the solution to be implemented using bash or it's utilities (as opposed to write something in yet another scripting language, such as Perl or Python).

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• -[NSConcreteMutableData release]: message sent to deallocated instance

  - by kamibutt

  Dear members, I am facing a problem of -[NSConcreteMutableData release]: message sent to deallocated instance, i have attached my sample code as well. - (IBAction)uploadImage { NSString *urlString = @"http://192.168.1.108/iphoneimages/uploadfile.php?userid=1&charid=23&msgid=3"; //if(FALSE) for (int i=0; i<[imgArray count]; i++) { // setting up the request object now NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init]; [request setURL:[NSURL URLWithString:urlString]]; [request setHTTPMethod:@"POST"]; /* add some header info now we always need a boundary when we post a file also we need to set the content type You might want to generate a random boundary.. this is just the same as my output from wireshark on a valid html post */ NSString *boundary = [NSString stringWithString:@"---------------------------14737809831466499882746641449"]; NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@",boundary]; [request addValue:contentType forHTTPHeaderField: @"Content-Type"]; /* now lets create the body of the post */ NSMutableData *body = [[NSMutableData data] autorelease]; NSString *str = [NSString stringWithFormat:@"Content-Disposition: form-data; name=\"userfile\"; filename=\"ipodfile%d.jpg\"\r\n",i]; [body appendData:[[NSString stringWithFormat:@"\r\n--%@\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]]; [body appendData:[[NSString stringWithString:str] dataUsingEncoding:NSUTF8StringEncoding]]; [body appendData:[[NSString stringWithString:@"Content-Type: application/octet-stream\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]]; NSData *imageData = UIImageJPEGRepresentation([imgArray objectAtIndex:i], 90); [body appendData:[NSData dataWithData:imageData]]; [body appendData:[[NSString stringWithFormat:@"\r\n--%@--\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]]; // setting the body of the post to the reqeust [request setHTTPBody:body]; // now lets make the connection to the web [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil]; //NSString *returnString = [[NSString alloc] initWithData:returnData encoding:NSUTF8StringEncoding]; //NSLog(@"%@",returnString); [imageData release]; [request release]; //[body release]; } } It successfully upload the images to the folder and there is no any error in the execution but when it complete it process and try to go back it give error -[NSConcreteMutableData release]: message sent to deallocated instance Please help me out. Thanks

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• Creating a mySQL query using PHP form dropdowns - If user ignores dropdown, do not filter by that pa

  - by user303043

  Hello, I am creating a simple MySQL query that will be built from the user selecting options from 2 dropdowns. The issue I am having is that I would like each drop down to default that if they do not actually choose an option, do not filter by that dropdown parameter. So, if they come in, and simply hit submit without choosing from a dropdown they should see everything. If they come in and pick from only one of the dropdowns, the query will basically ignore filtering by the other dropdown. I tried making <OPTION VALUE='any'>Choose but my query didn't know what to do with the 'any' and just shows no results. Here is my code. Thank you very much for whatever help you can provide. FORM <form method="POST" action="<?php echo $_SERVER['REQUEST_URI']; ?>"> <select name="GameType"> <OPTION VALUE='any'>Choose Game Type <option value="Game1">Option 1</option> <option value="Game2">Option 2</option> <option value="Game3">Option 3</option> </select> <select name="Instructor"> <OPTION VALUE='any'>Choose Instructor <option VALUE="InstructorA">Instructor A</option> <option value="InstructorB">Instructor B</option> <option value="InstructorC">Instructor C</option> </select> <input type='submit' value='Search Videos'> </form> MYSQL <?PHP connection stuff $db_handle = mysql_connect($server, $user_name, $password); $db_found = mysql_select_db($database, $db_handle); if ($db_found) { $SQL = "SELECT * FROM Videos WHERE GameType=\"{$_POST['GameType']}\" AND Instructor=\"{$_POST['Instructor']}\""; $result = mysql_query($SQL); while ($db_field = mysql_fetch_assoc($result)) { echo $db_field['ShortDescription'] . ", "; echo $db_field['LongDescription'] . ", "; echo $db_field['GameType'] . ", "; echo $db_field['NumberOfPlayers'] . ", "; echo $db_field['Instructor'] . ", "; echo $db_field['Stakes'] . ", "; echo $db_field['UserPermissionLevel'] . ", "; echo $db_field['DateCreated'] . "<BR>"; } mysql_close($db_handle); } else { print "Database NOT Found "; mysql_close($db_handle); } ?>

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• Getting this error while reading excel from c#

  - by Lalit

  Hello all, I have code string conn = @"Provider=Microsoft.ACE.OLEDB.12.0;DSN=Excel Files;DBQ=" + strSheetPath + @";DriverId=1046;FIL=excel 12.0;MaxBufferSize=2048;PageTimeout=5;"; //string conn = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + strSheetPath +";Extended Properties=Excel 12.0 Xml;HDR=YES;IMEX=1"; string destinationConnectionString = ConfigurationManager.ConnectionStrings["KGD6DBConnectionString"].ConnectionString; string query = "Select * From [Sheet1$]"; using (var myConnection = new OleDbConnection(conn)) using (var destinationConnection = new SqlConnection(destinationConnectionString)) using (var bulkCopy = new SqlBulkCopy(destinationConnection)) { //Map first column in source to second column in sql table (skipping the ID column). //Excel schema[CompanyName,Phone] Table schema[ShipperID, CompanyName, Phone] bulkCopy.ColumnMappings.Add(0, 1); bulkCopy.ColumnMappings.Add(1, 2); bulkCopy.ColumnMappings.Add(2, 3); bulkCopy.ColumnMappings.Add(3, 4); bulkCopy.ColumnMappings.Add(4, 5); bulkCopy.ColumnMappings.Add(5, 6); bulkCopy.ColumnMappings.Add(6, 7); bulkCopy.ColumnMappings.Add(7, 8); bulkCopy.ColumnMappings.Add(8, 9); bulkCopy.ColumnMappings.Add(9, 10); bulkCopy.ColumnMappings.Add(10, 11); bulkCopy.ColumnMappings.Add(11, 12); bulkCopy.ColumnMappings.Add(12, 13); bulkCopy.ColumnMappings.Add(13, 14); bulkCopy.ColumnMappings.Add(14, 15); bulkCopy.ColumnMappings.Add(15, 16); bulkCopy.ColumnMappings.Add(16, 17); bulkCopy.ColumnMappings.Add(17, 18); bulkCopy.ColumnMappings.Add(18, 19); bulkCopy.ColumnMappings.Add(19, 20); bulkCopy.ColumnMappings.Add(20, 21); bulkCopy.ColumnMappings.Add(21, 22); bulkCopy.ColumnMappings.Add(22, 23); bulkCopy.ColumnMappings.Add(23, 24); bulkCopy.DestinationTableName = "dbo.sampleInventory"; using (var myCommand = new OleDbCommand(query, myConnection)) { myConnection.Open(); destinationConnection.Open(); var myReader = myCommand.ExecuteReader(); while (myReader.Read()) { bulkCopy.WriteToServer(myReader); } } } return (new DataTable()); getting error on connection opening line. Error: Could not find installable ISAM.

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• Object relationships

  - by Hammerstein

  This stems from a recent couple of posts I've made on events and memory management in general. I'm making a new question as I don't think the software I'm using has anything to do with the overall problem and I'm trying to understand a little more about how to properly manage things. This is ASP.NET. I've been trying to understand the needs for Dispose/Finalize over the past few days and believe that I've got to a stage where I'm pretty happy with when I should/shouldn't implement the Dispose/Finalize. 'If I have members that implement IDisposable, put explicit calls to their dispose in my dispose method' seems to be my understanding. So, now I'm thinking maybe my understanding of object lifetimes and what holds on to what is just wrong! Rather than come up with some sample code that I think will illustrate my point, I'm going to describe as best I can actual code and see if someone can talk me through it. So, I have a repository class, in it I have a DataContext that I create when the repository is created. I implement IDisposable, and when my calling object is done, I call Dispose on my repository and explicitly call DataContext.Dispose( ). Now, one of the methods of this class creates and returns a list of objects that's handed back to my front end. Front End - Controller - Repository - Controller - Front End. (Using Redgate Memory Profiler, I take a snapshot of my software when the page is first loaded). My front end creates a controller object on page load and then makes a request to the repository sending back a list of items. When the page is finished loading, I call Dispose on the controller which in turn calls dispose on the context. In my mind, that should mean that my connection is closed and that I have no instances of my controller class. If I then refresh the page, it jumps to two 'Live' instances of the controller class. If I look at the object retention graph, the objects I created in my call to the list are being held onto ultimately by what looks like Linq. The controller/repository aside, if I create a list of objects somewhere, or I create an object and return it somewhere, am I safe to just assume that .NET will eventually come and clean things up for me or is there a best practice? The 'Live' instances suggest to me that these are still in memory and active objects, the fact that RMP apparently forces GC doesn't mean anything?

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• Device drivers and Windows

  - by b-gen-jack-o-neill

  Hi, I am trying to complete the picture of how the PC and the OS interacts together. And I am at point, where I am little out of guess when it comes to device drivers. Please, don´t write things like its too complicated, or you don´t need to know when using high programming laguage and winapi functions. I want to know, it´s for study purposes. So, the very basic structure of how OS and PC (by PC I mean of course HW) is how I see it is that all other than direct CPU commands, which can CPU do on itself (arithmetic operation, its registers access and memory access) must pass thru OS. Mainly becouse from ring level 3 you cannot use in and out intructions which are used for acesing other HW. I know that there is MMIO,but it must be set by port comunication first. It was not like this all the time. Even I am bit young to remember MSDOS, I know you could access HW directly, becouse there ws no limitation, no ring mode. So you could to write string to diplay use wheather DOS function, or directly acess video card memory and write it by yourself. But as OS developed, there is no longer this possibility. But it is fine, since OS now handles all the HW comunication, and frankly it more convinient and much more safe (I would say the only option) in multitasking environment. So nowdays you instead of using int instructions to use BIOS mapped function or DOS function you call dll which internally than handles everything you don´t need to know about. I understand this. I also undrstand that device drivers is the piece of code that runs in ring level 0, so it can do all the HW interactions. But what I don´t understand is connection between OS and device driver. Let´s take a example - I want to make a sound card make a sound. So I call windows API to acess sound card, but what happens than? Does windows call device drivers to do so? But if it does call device driver, does it mean, that all device drivers which can be called by winAPI function, must have routines named in some specific way? I mean, when I have new sound card, must its drivers have functions named same as the old one? So Windows can actually call the same function from its perspective? But if Windows have predefined sets of functions requored by device drivers, that it cannot use new drivers that doesent existed before last version of OS came out. Please, help me understand this mess. I am really getting mad. Thanks.

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• What is wrong with this attempt of sending a break-signal?

  - by Jook

  I have quite a headache about this seemingly easy task: send a break signal to my device, like the wxTerm (or any similar Terminal application) does. This signal has to be 125ms long, according to my tests and the devices specification. It should result in a specific response, but what I get is a longer response than expected, and the transmitted date is false. e.g.: what it should respond 08 00 81 00 00 01 07 00 what it does respond 08 01 0A 0C 10 40 40 07 00 7F What really boggles me is, that after I have used wxTerm to look at my available com-ports (without connecting or sending anything), my code starts to work! I can send then as many breaks as I like, I get my response right from then on. I have to reset my PC in order to try it again. What the heck is going on here?! Here is my code for a reset through a break-signal: minicom_client(boost::asio::io_service& io_service, unsigned int baud, const string& device) : active_(true), io_service_(io_service), serialPort(io_service, device) { if (!serialPort.is_open()) { cerr << "Failed to open serial port\n"; return; } boost::asio::serial_port_base::flow_control FLOW( boost::asio::serial_port_base::flow_control::hardware ); boost::asio::serial_port_base::baud_rate baud_option(baud); serialPort.set_option(FLOW); serialPort.set_option(baud_option); read_start(); std::cout << SetCommBreak(serialPort.native_handle()) << std::endl; std::cout << GetLastError() << std::endl; boost::posix_time::ptime mst1 = boost::posix_time::microsec_clock::local_time(); boost::this_thread::sleep(boost::posix_time::millisec(125)); boost::posix_time::ptime mst2 = boost::posix_time::microsec_clock::local_time(); std::cout << ClearCommBreak(serialPort.native_handle()) << std::endl; std::cout << GetLastError() << std::endl; boost::posix_time::time_duration msdiff = mst2 - mst1; std::cout << msdiff.total_milliseconds() << std::endl; } Edit: It was only necessary to look at the combo-box selection of com-ports of wxTerm - no active connection was needed to be established in order to make my code work. I am guessing, that there is some sort of initialisation missing, which is done, when wxTerm is creating the list for the serial-port combo-box.

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• IE sends multiple cookies with same name?

  - by akach

  I have a strange bug that occurs in IE7/XP and IE8/Vista on my website. IE sends two cookies named PHPSESSID. How to reproduce: Clear cookies in IE (not necessary if you never visited unisender.com). Visit unisender.com (exactly without www to reproduce!) and it will redirect to www.unisender.com Login with any valid username and password (I've registered username testmsdn with password testmsdn - feel free to use for testing) Run your favourite capture-the-traffic program (I prefer wireshark) Now click any menu link (e.g. "messages") Look at captured traffic - you will see that IE sends double PHPSESSID cookie (and you are logged out after click because of this). It seems like first PHPSESSID is from unisender.com and second from www.unisender.com. Captured sample: GET /en/letter_list HTTP/1.1 Accept: image/gif, image/jpeg, image/pjpeg, application/x-ms-application, application/vnd.ms-xpsdocument, application/xaml+xml, application/x-ms-xbap, application/x-shockwave-flash, / Referer: http://www.unisender.com/en/intro Accept-Language: ru User-Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.0; Trident/4.0; Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1) ; SLCC1; .NET CLR 2.0.50727; .NET CLR 3.5.21022; .NET CLR 3.5.30729; FDM; .NET CLR 3.0.30729) Accept-Encoding: gzip, deflate Host: www.unisender.com Connection: Keep-Alive Cookie: authchallenge=3a9cfcfc9fe33822e3e21d75c8a3d3e4; PHPSESSID=14ea1cb133632951592397c86eaf037e; us_reg_ref=unknown; us_reg_url=http%3A%2F%2Funisender.com%2F; __utma=1.778517853.1271204400.1271204400.1271204400.1; __utmb=1.3.10.1271204400; __utmc=1; __utmz=1.1271204400.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none); PHPSESSID=65e110aeb995a66b9dc8da5656c7a3da; last_login_name=testmsdn I've tried to use session and non-session cookies, tried to use .unisender.com instead of unisender.com for cookie - nothing helps. I suppose there should not be cookies with same name. Am I right? Is it a bug in IE? If it's a bug then is there a workaround? Or am I wrong and it's an expected behavior?

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• Architectural Design for a Data-Driven Silverlight WP7 app

  - by Rosarch

  I have a Silverlight Windows Phone 7 app that pulls data from a public API. I find myself doing much of the same thing over and over again: In the UI, set a loading message or loading progress bar in place of where the content is Get the content, which may be already in memory, cached in isolated file storage, or require an HTTP request If the content can not be acquired (no network connection, etc), display an error message If the content is acquired, display it in the UI Keep the content in main memory for subsequent queries The content that is displayed to the user can be taken directly from a data source, such as an ObservableCollection, or it may be a query on a data source. I would like to factor out this repetitive process into a framework where ideally only the following needs to be specified: Where to display the content in the UI The UI elements to show while loading, on failure, and on success The URI of the HTTP request How to parse the HTTP response into the data structure that will kept in memory The location of the file in isolated storage, if it exists How to parse the file contents into the data structure that will be kept in memory It may sound like a lot, but two strings, three FrameworkElements, and two methods is less than the overhead that I currently have. Also, this needs to work for however the data is maintained in memory, and needs to work for direct collections and queries on those collections. My questions are: Has something like this already been implemented? Are my thoughts about the topic above fundamentally wrong in some way? Here is a design I'm thinking of: There are two components, a View and a Model. The View is given the FrameworkElements for loading, failure, and success. It is also given a reference to the corresponding Model. The View is a UserControl that is placed somewhere in the UI. The Model a class that is given the URI for the data, a method of how to parse the data, and optionally a filename and how to parse the file. It is responsible for retrieving the data and notifying the View whenever the current status (loading/fail/success) changes. If the data downloaded from the network is different from the cache, the network data takes precedence. When the app closes or is tombstoned, the model writes the data to the cache. How does that sound?

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• Model self referential collections in Rails

  - by Najitaka

  I have written an application for an online clothing store in Rails 2.3.5. I want to show related Products when a customer views the Product Detail page. For example, if the customer views the detail page for a suit, I'd like to display the accessory products that match the dress such as a vest, shoes, and belt. I have named the related products an Ensemble. However, the vest, shoes, and belts are also Products which is what has me struggling. I have it working as follows but I know it's not the Rails way. I have a Products table for all of the products. Not important here but I also have a ProductDetails table. I have an Ensembles table that has the following columns: product_id - the main or origination product, the one displayed on the detail page outfit_id - the related or accessory product In setting up the data, on the Products list, for each Product I have an Ensemble link. This link takes you to the index action in the Ensembles controller. Using the id from the "main" Product, I find all of the associated Ensemble rows by product_id or I create a new ensemble and assign the id from the main product as the product_id. I'd like to just be able to do @product.related_products to get an Ensemble collection. Also on the index page I list the columns of the main product so the user can be sure their main product was the one they selected from the list. I also have a select list of the other products, with an Add to Ensemble action. Finally on the same index page, I have a table that displays the products that are already in the ensemble and in that list each row has a destroy link to remove a particular product from the ensemble. It would be nice if given a single Ensemble row @ensemble I could do @ensemble.product to get the Product related to the outfit_id of the ensemble row. I've got it working without associations but I have to run queries in the controller to build my own @product, @ensemble, and @ensembles collections. Also the only way I found to destroy an ensemble row is by Ensemble.connection.delete(sql to delete), simple @ensemble.destroy doesn't work. Anyone know how I would set up the associations or have a link to a site explaining a similar setup. None of the examples I found use the same table. They have A related to B through C. I want A related to other A through B.

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• Large transactions causing "System.Data.SqlClient.SqlException: Timeout expired" error?

  - by Michael

  My application requires a user to log in and allows them to edit a list of things. However, it seems that if the same user always logs in and out and edits the list, this user will run into a "System.Data.SqlClient.SqlException: Timeout expired." error. I've read comments about increasing the timeout period but I've also read a comment about it possibly caused by uncommitted transactions. And I do have one going in the application. I'll provide the code I'm working with and there is an IF statement in there that I was a little iffy about but it seemed like a reasonable thing to do. I'll just go over what's going on here, there is a list of objects to update or add into the database. New objects created in the application are given an ID of 0 while existing objects have their own ID's generated from the DB. If the user chooses to delete some objects, their IDs are stored in a separate list of Integers. Once the user is ready to save their changes, the two lists are passed into this method. By use of the IF statement, objects with ID of 0 are added (using the Add stored procedure) and those objects with non-zero IDs are updated (using the Update stored procedure). After all this, a FOR loop goes through all the integers in the "removal" list and uses the Delete stored procedure to remove them. A transaction is used for all this. Public Shared Sub UpdateSomethings(ByVal SomethingList As List(Of Something), ByVal RemovalList As List(Of Integer)) Using DBConnection As New SqlConnection(conn) DBConnection.Open() Dim MyTransaction As SqlTransaction MyTransaction = DBConnection.BeginTransaction() Try For Each SomethingItem As Something In SomethingList Using MyCommand As New SqlCommand() MyCommand.Connection = DBConnection If SomethingItem.ID > 0 Then MyCommand.CommandText = "UpdateSomething" Else MyCommand.CommandText = "AddSomething" End If MyCommand.Transaction = MyTransaction MyCommand.CommandType = CommandType.StoredProcedure With MyCommand.Parameters If MyCommand.CommandText = "UpdateSomething" Then .Add("@id", SqlDbType.Int).Value = SomethingItem.ID End If .Add("@stuff", SqlDbType.Varchar).Value = SomethingItem.Stuff End With MyCommand.ExecuteNonQuery() End Using Next For Each ID As Integer In RemovalList Using MyCommand As New SqlCommand("DeleteSomething", DBConnection) MyCommand.Transaction = MyTransaction MyCommand.CommandType = CommandType.StoredProcedure With MyCommand.Parameters .Add("@id", SqlDbType.Int).Value = ID End With MyCommand.ExecuteNonQuery() End Using Next MyTransaction.Commit() Catch ex As Exception MyTransaction.Rollback() 'Exception handling goes here End Try End Using End Sub There are three stored procedures used here as well as some looping so I can see how something can be holding everything up if the list is large enough. Other users can log in to the system at the same time just fine though. I'm using Visual Studio 2008 to debug and am using SQL Server 2000 for the DB.

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• Message passing chrome extension

  - by Mayur Kataria

  I wants to create an extension where content script will send message to background page and then on browser action means clicking on extension icon will access that background page and get some data.I am using chrome Version 23.0.1271.64 m on windows8. I am getting following error. Port error: Could not establish connection. Receiving end does not exist. I tried to solve the same. but people are using sendRequest which is not supported by chrome20+. i also found solution mentioned for chrome 20+. But not working. Please help. Below is the file contents. manifest.json { "name": "Test Extension", "version": "1.0", "manifest_version": 2, "description": "A test extension.", "background": "background.html", "content_scripts": [ { "matches": ["<all_urls>"], "js": ["jquery.js","content.js"] } ], "permissions": ["tabs", "http://*/", "https://*/"], "browser_action": { "default_icon": "icon.png", "default_popup": "popup.html" } } background.html <html> <head> <script src="background.js"></script> </head> <body> <h1>Wy</h1> </body> </html> background.js chrome.extension.onMessage.addListener(function(request, sender, sendResponse) { // Chrome 20+ alert(request); console.log('received in listener'); sendResponse({farewell: "goodbye"}); }); content.js $(function(){ console.log('start-sending message'); chrome.extension.sendMessage({greeting: "hello"},function(response){alert(response);}); console.log('end-sending message'); }); popup.html <!doctype html> <html> <head> <title>Getting Started Extension's Popup</title> </style> <!-- JavaScript and HTML must be in separate files for security. --> <script src="jquery.js"></script> <script src="popup.js"></script> </head> <body> </body> </html> popup.js $(function(){ var str_html = "<tr><td width='60%'>S</td><td width='40%'>15</td></tr><tr><td width='60%'>M</td><td width='40%'>25</td></tr>"; $('#sizes_container').html(str_html); var bkg = chrome.extension.getBackgroundPage(); console.log(bkg); });

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• ob_start() -> ob_flush() doesn't work

  - by MB34

  I am using ob_start()/ob_flush() to, hopefully, give me some progress during a long import operation. Here is a simple outline of what I'm doing: <?php ob_start (); echo "Connecting to download Inventory file.<br>"; $conn = ftp_connect($ftp_site) or die("Could not connect"); echo "Logging into site download Inventory file.<br>"; ftp_login($conn,$ftp_username,$ftp_password) or die("Bad login credentials for ". $ftp_site); echo "Changing directory on download Inventory file.<br>"; ftp_chdir($conn,"INV") or die("could not change directory to INV"); // connection, local, remote, type, resume $localname = "INV"."_".date("m")."_".date('d').".csv"; echo "Downloading Inventory file to:".$localname."<br>"; ob_flush(); flush(); sleep(5); if (ftp_get($conn,$localname,"INV.csv",FTP_ASCII)) { echo "New Inventory File Downloaded<br>"; $datapath = $localname; ftp_close($conn); } else { ftp_close($conn); die("There was a problem downloading the Inventory file."); } ob_flush(); flush(); sleep(5); $csvfile = fopen($datapath, "r"); // open csv file $x = 1; // skip the header line $line = fgetcsv($csvfile); $y = (feof($csvfile) ? 2 : 5); while ((!$debug) ? (!feof($csvfile)) : $x <= $y) { $x++; $line = fgetcsv($csvfile); // do a lot of import stuff here with $line ob_flush(); flush(); sleep(1); } fclose($csvfile); // important: close the file ob_end_clean(); However, nothing is being output to the screen at all. I know the data file is getting downloaded because I watch the directory where it is being placed. I also know that the import is happening, meaning that it is in the while loop, because I can monitor the DB and records are being inserted. Any ideas as to why I am not getting output to the screen?

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• Efficiently fetching and storing tweets from a few hundred twitter profiles?

  - by MSpreij

  The site I'm working on needs to fetch the tweets from 150-300 people, store them locally, and then list them on the front page. The profiles sit in groups. The pages will be showing the last 20 tweets (or 21-40, etc) by date, group of profiles, single profile, search, or "subject" (which is sort of a different group.. I think..) a live, context-aware tag cloud (based on the last 300 tweets of the current search, group of profiles, or single profile shown) various statistics (group stuffs, most active, etc) which depend on the type of page shown. We're expecting a fair bit of traffic. The last, similar site peaked at nearly 40K visits per day, and ran intro trouble before I started caching pages as static files, and disabling some features (some, accidently..). This was caused mostly by the fact that a page load would also fetch the last x tweets from the 3-6 profiles which had not been updated the longest.. With this new site I can fortunately use cron to fetch tweets, so that helps. I'll also be denormalizing the db a little so it needs less joins, optimize it for faster selects instead of size. Now, main question: how do I figure out which profiles to check for new tweets in an efficient manner? Some people will be tweeting more often than others, some will tweet in bursts (this happens a lot). I want to keep the front page of the site as "current" as possible. If it comes to, say, 300 profiles, and I check 5 every minute, some tweets will only appear an hour after the fact. I can check more often (up to 20K) but want to optimize this as much as possible, both to not hit the rate limit and to not run out of resources on the local server (it hit mysql's connection limit with that other site). Question 2: since cron only "runs" once a minute, I figure I have to check multiple profiles each minute - as stated, at least 5, possibly more. To try and spread it out over that minute I could have it sleep a few seconds between batches or even single profiles. But then if it takes longer than 60 seconds altogether, the script will run into itself. Is this a problem? If so, how can I avoid that? Question 3: any other tips? Readmes? URLs?

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• What is the best way to connect to an Oracle database to build my own IDE? [closed]

  - by rima

  before answer me plz thinking about the futures of these kind of program and answer me plz. I wanna get some data from oracle server like: 1-get all the function,package,procedure and etc for showing them or drop them & etc... 2-compile my *.sql files,get the result if they have problem & etc... becuz I was beginner in oracle first of all I for solve the second problem I try to connect to sqlPlus by RUN sqlplus and trace the output(I mean,I change the output stream of shell and trace what happend and handle the assigned message to customer. NOW THIS PART SUCCEED. just a little bit I have problem with get all result because the output is asynchronous.any way... [in this case I log in to oracle Server by send argument to the sqlplus by make a process in c#] after that I try to get all function,package or procedure name,but I have problem in speed!so I try to use oracle.DataAccess.dll to connect the database. now I m so confusing about: which way is correct way to build a program that work like Oracle Developer! I do not have any experience for like these program how work. If Your answer is I must use the second way follow this part plz: I search a little bit the Golden,PLedit (Benthic software),I have little bit problem how I must create the connection string?because I thinking about how I can find the host name or port number that oracle work on them?? am I need read the TNSNames.Ora file? IF your answer is I must use the first way follow this part plz: do u have any Idea for how I parse the output?because for example the result of a table is so confusing...[i can handle & program it but I really need someone experience,because the important things to me learn how such software work so nice and with quick response?] All of the has different style in output... If you are not sure Can u help me which book can help me in this way i become expert? becuz for example all the C# write just about how u can connect to DB and the DB books write how u can use this DB program,I looking for a book that give me some Idea how develop an interface for do transaction between these two.not simple send and receive data,for example how write a compiler for them. the language of book is not different for me i know C#,java,VB,sql,Oracle Thanks.

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• Android: How to properly exit application when inconsistent condition is unavoidable?

  - by Bevor

  First of all I already read about all this discussion that it isn't a good idea to manually exit an Android application. But in my case it seems to be needed. I have an AsyncTask which does a lof of operations in background. That means downloading data, saving it to local storage and preparing it for usage in application. It could happen that there is no internet connection or something different happens. For all that cases I have an Exception handling which returns the result. And if there is an exception, the application is unusable so I need to exit it. My question is, do I have to do some unregistration unloading or unbinding tasks or something when I exit the application by code or is System.exit(0) ok? I do all this in an AsyncTask, see my example: public class InitializationTask extends AsyncTask<Void, Void, InitializationResult> { private ProcessController processController = new ProcessController(); private ProgressDialog progressDialog; private Activity mainActivity; public InitializationTask(Activity mainActivity) { this.mainActivity = mainActivity; } @Override protected void onPreExecute() { super.onPreExecute(); progressDialog = new ProgressDialog(mainActivity); progressDialog.setMessage("Die Daten werden aufbereitet.\nBitte warten..."); progressDialog.setIndeterminate(true); //means that the "loading amount" is not measured. progressDialog.setCancelable(false); progressDialog.show(); }; @Override protected InitializationResult doInBackground(Void... params) { return processController.initializeData(); } @Override protected void onPostExecute(InitializationResult result) { super.onPostExecute(result); progressDialog.dismiss(); if (!result.isValid()) { AlertDialog.Builder dialog = new AlertDialog.Builder(mainActivity); dialog.setTitle("Initialisierungsfehler"); dialog.setMessage(result.getReason()); dialog.setPositiveButton("Ok", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { dialog.cancel(); //TODO cancel application System.exit(0); } }); dialog.show(); } } }

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• expecte ')' before className

  - by Akbarbuneri

  Hi I have a class DataObject as Header ::: #import <Foundation/Foundation.h> @interface DataObject : NSObject { NSString *erorrMessage; BOOL hasError; NSDictionary *dataValues; } @property(nonatomic, retain)NSString *erorrMessage; @property(nonatomic)BOOL hasError; @property(nonatomic, retain)NSDictionary *dataValues; @end Class Implementation:::: #import "DataObject.h" @implementation DataObject @synthesize erorrMessage; @synthesize hasError; @synthesize dataValues; @end And I have another class as DataManager Header as :::: #import <Foundation/Foundation.h> @interface DataManager : NSObject - (DataObject *)getData :(NSString*)url; @end Implementation :::: #import "DataManager.h" #import "DataObject.h" #import "JSON.h" @implementation DataManager - (DataObject *)getData :(NSString*)url{ DataObject* dataObject = [[DataObject alloc]init]; NSString *urlString = [NSString stringWithFormat:url]; NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:urlString]]; //TODO: Here we have to check the internet connection before requesting. NSError * erorrOnRequesting; NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:&erorrOnRequesting]; NSString* responseString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]; if( erorrOnRequesting != nil) { dataObject.hasError = YES; dataObject.erorrMessage = @"Error on requsting to the web server"; return dataObject; } NSError *errorOnParsing; SBJSON *json = [[SBJSON new] autorelease]; NSDictionary *dataValues = [json objectWithString:responseString error:&errorOnParsing]; [responseString release]; if(errorOnParsing != nil) { //TODO: We have to send the website a feedback that there is some problem on the server end. dataObject.hasError = YES; dataObject.erorrMessage = @"Error on parsing, the server returned invalid data."; return dataObject; } dataObject.hasError = NO; dataObject.dataValues = dataValues; return dataObject; } @end Now when I build I got an error in the DataManager header where I #import Dataobject header, it says "error: expected')' before DataObject" I don;t understand what I miss. Thanks for the help..

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• GKSession sendDataToAllPeers getting invalid parameter

  - by cb4

  This is my first post and I wanted to start it by thanking the many stackoverflow contributors who will never know how much they helped me out these past several days as I worked to complete my first iOS app. I am indebted to them and to this site for giving them a place to post. To 'pay off' some of that debt, I hope this will help others as I have been helped... So, my app uses the GKPeerPickerController to make a connection to a 2nd device. Once connected, the devices can send text messages to each other. The receiving peer has the message displayed in a UIAlertView. Everything was working fine. Then I decided to experiment with locations and added code to get the current location. I convert it into latitude & longitude in degrees, minutes, and seconds and put them into one NSString. I added a button to my storyboard called 'Send Location' which, when tapped, sends the location to the connected peer. This is where I ran into the problem. Both the send text and send location methods call the sendPacket method with a NSString. sendPacket converts the string to NSData and calls sendDataToAllPeers. When I learned how to capture the error, it was "Invalid parameter for - sendDataToAllPeers:withDataMode:error:". [.....pause.....] Well, this was going to be a question but in writing all this to explain the problem, the answer just dawned on me. Did a few tests and verified it now works. The issue was not in sendDataToAllPeers, it was in the conversion of the NSString (strToSend) to NSData: packet = [strToSend dataUsingEncoding:NSASCIIStringEncoding]; Specifically, it was the degree sign character (little circle, ASCII 176). NSASCIIStringEncoding only includes ASCII characters up to 127 so don't use any above that. I'm sure there was a quicker way to find the problem, but I don't know Objective-C or Xcode's debugging facility well enough yet. Whew! Several hours to discover that little tidbit. I did learn a lot, though, and that's always a good thing!

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• C#, cannot understand this error?

  - by 5YrsLaterDBA

  I am using VS2008. I have a project, SystemSoftware project, connect with a database and we are using L2E. I have a RuntimeInfo class which contains some shared information there. It looks like this: public class RuntimeInfo { public const int PWD_ExpireDays = 30; private static RuntimeInfo thisObj = new RuntimeInfo(); public static string AndeDBConnStr = ConfigurationManager.ConnectionStrings["AndeDBEntities"].ConnectionString; private RuntimeInfo() { } /// <summary> /// /// </summary> /// <returns>Return this singleton object</returns> public static RuntimeInfo getRuntimeInfo() { return thisObj; } } Now I added a helper project, AndeDataViewer, to the solution which creates a simple UI to display data from the database for testing/verification purpose. I don't want to create another set of Entity Data Model in the helper project. I just added all related files as a link in the new helper project. In the AndeDataViewer project, I get the connection string from above RuntimeInfo class which is a class from my SystemSoftware project as a linked file. The code in AndeDataViewer is like this: public class DbAccess : IDisposable { private String connStr = String.Empty; public DbAccess() { connStr = RuntimeInfo.AndeDBConnStr; } } My SystemSoftware works fine that means the RuntimeInfo class has no problem there. But when I run my AndeDataViewer, the statement inside above constructor, connStr = RuntimeInfo.AndeDBConnStr; , throws an exception. The exception is copied here: System.TypeInitializationException was unhandled Message="The type initializer for 'MyCompany.SystemSoftware.SystemInfo.RuntimeInfo' threw an exception." Source="AndeDataViewer" TypeName="MyCompany.SystemSoftware.SystemInfo.RuntimeInfo" StackTrace: at AndeDataViewer.DbAccess..ctor() in C:\workspace\SystemSoftware\Other\AndeDataViewer\AndeDataViewer\DbAccess.cs:line 17 at AndeDataViewer.Window1.rbRawData_Checked(Object sender, RoutedEventArgs e) in C:\workspace\SystemSoftware\Other\AndeDataViewer\AndeDataViewer\Window1.xaml.cs:line 69 at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs) .... InnerException: System.NullReferenceException Message="Object reference not set to an instance of an object." Source="AndeDataViewer" StackTrace: at MyCompany.SystemSoftware.SystemInfo.RuntimeInfo..cctor() in C:\workspace\SystemSoftware\SystemSoftware\src\systeminfo\RuntimeInfo.cs:line 24 InnerException: I cannot understand this because it looks fine to me but why there is an exception? we cannot access static variable when a class is a linked class? A linked class should be the same as the local class I think. "Linked" here means when I add file I use "Add As Link".

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