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• How to implement dual communication between server and client via http

  - by Alex Sebastiano

  I have a AJAX client which must receive messages from server. Some messages from server not like request-response type. For example, imaging game in which players can enter. Server must send to client info about player entering. But how can server send message to client via http without request from client? Only decision that i can invent: client send request to server (getNewPlayerEnter request) with big timeout, server checks state of player set, if in set new players are, then server send info to client, if not server 'sleeps' on some time, and after 'sleeping' server checks players set again. I think my desicion a little stupid(maybe not little). How implement it right? p.s. sorry for my english

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• HTTP Download very Big File

  - by Luca

  I'm working at a web application in Python/Twisted. I want the user to be able to download a very big file ( 100 Mb). I don't want to load all the file in memory (of the server), of course. server side I have this idea: ... request.setHeader('Content-Type', 'text/plain') fp = open(fileName, 'rb') try: r = None while r != '': r = fp.read(1024) request.write(r) finally: fp.close() request.finish() I expected this to work, but I have problems: I'm testing with FF... It seems the browser make me wait until the file is completed downloaded, and then I have the open/save dialog box. I expected the dialog box immediately, and then the progress bar in action... Maybe I have to add something in the Http header... Something like the size of the file?

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• Why "Content-Length: 0" in POST requests?

  - by stesch

  A customer sometimes sends POST requests with Content-Length: 0 when submitting a form (10 to over 40 fields). We tested it with different browsers and from different locations but couldn't reproduce the error. The customer is using Internet Explorer 7 and a proxy. We asked them to let their system administrator see into the problem from their side. Running some tests without the proxy, etc.. In the meantime (half a year later and still no answer) I'm curious if somebody else knows of similar problems with a Content-Length: 0 request. Maybe from inside some Windows network with a special proxy for big companies. Is there a known problem with Internet Explorer 7? With a proxy system? The Windows network itself? Google only showed something in the context of NTLM (and such) authentication, but we aren't using this in the web application. Maybe it's in the way the proxy operates in the customer's network with Windows logins? (I'm no Windows expert. Just guessing.) I have no further information about the infrastructure.

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• Java HTTP Request Occasionally Hangs

  - by behrk2

  Hello Everyone, For the majority of the time, my HTTP Requests work with no problem. However, occasionally they will hang. The code that I am using is set up so that if the request succeeds (with a response code of 200 or 201), then call screen.requestSucceeded(). If the request fails, then call screen.requestFailed(). When the request hangs, however, it does so before one of the above methods are called. Is there something wrong with my code? Should I be using some sort of best practice to prevent any hanging? The following is my code. I would appreciate any help. Thanks! HttpConnection connection = (HttpConnection) Connector.open(url + connectionParameters); connection.setRequestMethod(method); connection.setRequestProperty("WWW-Authenticate", "OAuth realm=api.netflix.com"); if (method.equals("POST")) { connection.setRequestProperty("Content-type", "application/x-www-form-urlencoded"); } int responseCode = connection.getResponseCode(); System.out.println("RESPONSE CODE: " + responseCode); if (connection instanceof HttpsConnection) { HttpsConnection secureConnection = (HttpsConnection) connection; String issuer = secureConnection.getSecurityInfo() .getServerCertificate().getIssuer(); UiApplication.getUiApplication().invokeLater( new DialogRunner( "Secure Connection! Certificate issued by: " + issuer)); } if (responseCode != 200 && responseCode != 201) { screen.requestFailed("Unexpected response code: " + responseCode); connection.close(); return; } String contentType = connection.getHeaderField("Content-type"); ByteArrayOutputStream baos = new ByteArrayOutputStream(); InputStream responseData = connection.openInputStream(); byte[] buffer = new byte[20000]; int bytesRead = 0; while ((bytesRead = responseData.read(buffer)) > 0) { baos.write(buffer, 0, bytesRead); } baos.close(); connection.close(); screen.requestSucceeded(baos.toByteArray(), contentType); } catch (IOException ex) { screen.requestFailed(ex.toString()); }

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• HTTPS Redirect Causing Error "Server cannot append header after HTTP headers have been sent"

  - by Chad

  I need to check that our visitors are using HTTPS. In BasePage I check if the request is coming via HTTPS. If it's not, I redirect back with HTTPS. However, when someone comes to the site and this function is used, I get the error: System.Web.HttpException: Server cannot append header after HTTP headers have been sent. at System.Web.HttpResponse.AppendHeader(String name, String value) at System.Web.HttpResponse.AddHeader(String name, String value) at Premier.Payment.Website.Generic.BasePage..ctor() Here is the code I started with: // If page not currently SSL if (HttpContext.Current.Request.ServerVariables["HTTPS"].Equals("off")) { // If SSL is required if (GetConfigSetting("SSLRequired").ToUpper().Equals("TRUE")) { string redi = "https://" + HttpContext.Current.Request.ServerVariables["SERVER_NAME"].ToString() + HttpContext.Current.Request.ServerVariables["SCRIPT_NAME"].ToString() + "?" + HttpContext.Current.Request.ServerVariables["QUERY_STRING"].ToString(); HttpContext.Current.Response.Redirect(redi.ToString()); } } I also tried adding this above it (a bit I used in another site for a similar problem): // Wait until page is copletely loaded before sending anything since we re-build HttpContext.Current.Response.BufferOutput = true; I am using c# in .NET 3.5 on IIS 6. enter code here

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• what can be causes of http server crash?

  - by mithunmo

  Hello , I am using WAMP server on Windows XP. - Apache 2.2.11 - MySQL 5.1.36 (INNODB engine) - PHP 5.3.0 I observe that my WAMP server crashes in the following scenarios 1) IF I use a Low end PC ( low processor speed and low RAM) 2) After making some changes to httpd.conf file .For eg changing the Allow from IP address . But here it crashes only once and then it starts to work fine. 3) Random crashes CRASH LOG szAppName : httpd.exe szAppVer : 2.2.11.0 szModName : php5ts.dll szModVer : 5.3.0.0 offset : 0000c309 C:\DOCUME~1\blrcom\LOCALS~1\Temp\WERc677.dir00\httpd.exe.mdmp C:\DOCUME~1\blrcom\LOCALS~1\Temp\WERc677.dir00\appcompat.txt My questions 1) Does high CPU utilization/LOW RAM can also cause the HTTP server to crash ? 2) excessive file reading as in every 10 seconds ? 3) unlimited script execution time . I have set the maximum execution time in php script to 0 as my script has to execute for sometimes 2-3 days. Is there any way to avoid this ? 4) Access to Database ? Should we use lock before reading and writing Can these be the reasons for random wamp server crashes ? OR is is some other programming error ? Please guide me . Regards, Mithun

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• Java HTTP Requests Buffer size

  - by behrk2

  Hello, I have an HTTP Request Dispatcher class that works most of the time, but I had noticed that it "stalls" when receiving larger requests. After looking into the problem, I thought that perhaps I wasn't allocating enough bytes to the buffer. Before, I was doing: byte[] buffer = new byte[10000]; After changing it to 20000, it seems to have stopped stalling: String contentType = connection.getHeaderField("Content-type"); ByteArrayOutputStream baos = new ByteArrayOutputStream(); InputStream responseData = connection.openInputStream(); byte[] buffer = new byte[20000]; int bytesRead = responseData.read(buffer); while (bytesRead > 0) { baos.write(buffer, 0, bytesRead); bytesRead = responseData.read(buffer); } baos.close(); connection.close(); Am I doing this right? Is there anyway that I can dynamically set the number of bytes for the buffer based on the size of the request? Thanks...

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• Sharing session variables from http and https versio

  - by tangurena

  I am trying to fix an ASP.NET site that a friend had botched converting from older technologies. To the user, the site appears to have public and secured sections. Behind the scenes, the public and private sites are separate web applications with separate app pools. The difficulty arises because it appears that the applications share the same session IDs (when going from the public to the secured pages, the session ID remains the same), yet none of the (InProc) session variables are getting passed from the public site to the private one. Basically, the workflow consists of the user checking a checkbox ("I agree" type of stuff) on the public site (let's call that page http://www.boring.gov/iAgree.aspx), then logging in on the secured site (let's call that page https://www.boring.gov/login.aspx). The commandments from the parent agency in DC are that the user may not bookmark the login page, the user has to click "I agree" every time they log in, and that the "I agree" stuff has to be on a separate page. What am I missing? How would you do it? Notes: 1 - This is getting hosted on a single Windows 2003 server. 2 - Yes, it is a government agency. 3 - I would have done things very differently if I was doing the conversion, but I wasn't brought in until the poop hit the fan, and it is too late to redo things. 4 - Two previous SO threads that appear to be related, yet don't apply are this and that

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• How to handle building and parsing HTTP URL's / URI's / paths in Perl

  - by Robert S. Barnes

  I have a wget like script which downloads a page and then retrieves all the files linked in img tags on that page. Given the URL of the original page and the the link extracted from the img tag in that page I need to build the URL for the image file I want to retrieve. Currently I use a function I wrote: sub build_url { my ( $base, $path ) = @_; # if the path is absolute just prepend the domain to it if ($path =~ /^\//) { ($base) = $base =~ /^(?:http:\/\/)?(\w+(?:\.\w+)+)/; return "$base$path"; } my @base = split '/', $base; my @path = split '/', $path; # remove a trailing filename pop @base if $base =~ /[[:alnum:]]+\/[\w\d]+\.[\w]+$/; # check for relative paths my $relcount = $path =~ /(\.\.\/)/g; while ( $relcount-- ) { pop @base; shift @path; } return join '/', @base, @path; } The thing is, I'm surely not the first person solving this problem, and in fact it's such a general problem that I assume there must be some better, more standard way of dealing with it, using either a core module or something from CPAN - although via a core module is preferable. I was thinking about File::Spec but wasn't sure if it has all the functionality I would need.

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• Forwarding HTTP Request with Direct Server Return

  - by Daniel Crabtree

  I have servers spread across several data centers, each storing different files. I want users to be able to access the files on all servers through a single domain and have the individual servers return the files directly to the users. The following shows a simple example: 1) The user's browser requests http://www.example.com/files/file1.zip 2) Request goes to server A, based on the DNS A record for example.com. 3) Server A analyzes the request and works out that /files/file1.zip is stored on server B. 4) Server A forwards the request to server B. 5) Server B returns file1.zip directly to the user without going through server A. Note: steps 4 and 5 must be transparent to the user and cannot involve sending a redirect to the user as that would violate the requirement of a single domain. From my research, what I want to achieve is called "Direct Server Return" and it is a common setup for load balancing. It is also sometimes called a half reverse proxy. For step 4, it sounds like I need to do MAC Address Translation and then pass the request back onto the network and for servers outside the network of server A tunneling will be required. For step 5, I simply need to configure server B, as per the real servers in a load balancing setup. Namely, server B should have server A's IP address on the loopback interface and it should not answer any ARP requests for that IP address. My problem is how to actually achieve step 4? I have found plenty of hardware and software that can do this for simple load balancing at layer 4, but these solutions fall short and cannot handle the kind of custom routing I require. It seems like I will need to roll my own solution. Ideally, I would like to do the routing / forwarding at the web server level, i.e. in PHP or C# / ASP.net. However, I am open to doing it at a lower level such as Apache or IIS, or at an even lower level, i.e. a custom proxy service in front of everything.

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• Perl: Value of response code in HTTP::Request

  - by lola

  Hi all, So, I am writing a code to get a document from the internet. The document size is around 200 KB. This is the code: !/usr/local/bin/perl -w use strict; use LWP::UserAgent; my $ua = LWP::UserAgent->new; my $url = "SOME URL"; my $req = HTTP::Request->new(GET => $url); my $res = $ua->request($req); if($res->is_success){ print $res->content ."\n"; } else{ print "Error: " . $res->status_line; } Now, the only problem is I can't mention what the URL is. However, the output is: "Error: 500 read timeout". When I checked the link externally, the data is being downloaded in under 5 seconds. I even changed the timeout to 1000s, but it still didn't work. How should I go about finding more information related to the response. The size of the file (around 200KB) is also not too great to warrant a read timeout. The server is also not a busy one, didn't give a problem whenever I checked the link on the browser. Thanks.

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• Write transparent HTTP Proxy script in PHP

  - by Leo Izen

  Is there an easy forwarding/transparent php proxy script that I can host on my web server? These are my conditions: I'm using free web hosting, so I have pretty much no control over my machine. Otherwise I could use Perl's HTTP::Proxy module. This means no root password. It does run php though. I already have a server running on port 80. What I mean is I would like to put a php script as index.php on my server that will forward all requests. I don't want a script like PHProxy or Glype where I go to the site, then enter a URL. I want a server so I can enter proxy.example.com:80 in Firefox's or IE's or whatever's proxy settings and it will forward all requests to the server. Preferably (though not fatal if not possible) I would like for it to pass on the USER_AGENT environmental variable (That's the browser) instead of setting itself to be the USER_AGENT I can't start a new Daemon. My server won't allow it. Is there a script that will do this? If so, which?

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• Configuring Oracle HTTP Server 12c for WebLogic Server Domain

  - by Emin Askerov

  Oracle HTTP Server (OHS) 12c 12.1.2 which was released in July 2013 as a part of Oracle Web Tier 12c is the web server component of Oracle Fusion Middleware. In essence this is Apache HTTP Server 2.2.22 (with critical bug fixes from higher versions) which includes modules developed specifically by Oracle. It provides a listener functionality for Oracle WebLogic Server and the framework for hosting static pages, dynamic pages, and applications over the Web. OHS can be easily managed by Weblogic Management Framework, a set of tools which provides administrative capabilities (start, stop, lifecycle operations, etc.) for Oracle Fusion Middleware products. In other words all tools which are familiar to us (Node Manager, WLST, Administration Console, Fusion Middleware Control etc.) presented as a part of Weblogic Management Framework and using for managing Java and System Components both for Weblogic Server and Standalone Domain types. You can familiarize yourself with these terms using related documentation: 1. Introduction to Oracle HTTP Server: http://docs.oracle.com/middleware/1212/webtier/index.html 2. Weblogic Management Framework: http://docs.oracle.com/middleware/1212/core/ASCON/terminology.htm#ASCON11260 In the given post I would like to cover rather simple use case how to configure OHS as web proxy in Weblogic Cluster environment. For example, we have existing Weblogic Domain where some managed servers have been joined to cluster and host business applications. We need to configure web proxy component which will act as entry point, load balancer for our cluster for user requests. Of course, we could install old good Apache HTTP Server and configure mod_wl plugin. However this solution not optimal from manageability perspective: we need to install Apache, install additional plugin then configure it by editing configuration file which is not really convenient for FMW Administrators and often increase time of performing of simple administrative task. Alternatively, we could use OHS as System Component within Weblogic Domain and use full power of Weblogic Management Framework in order to configure, manage and monitor it! I like this idea! What about you? I hope after reading this post you will agree with me. First of all it is necessary to download OHS binaries. You can use this link for downloading: http://www.oracle.com/technetwork/java/webtier/downloads/index2-303202.html As we will use Fusion Middleware Control for managing OHS instances it is necessary to extend your domain with Enterprise Manager and Oracle ADF and JRF templates. This is not topic for focusing in this post, but you could get more information from documentation or one of my previous posts: http://docs.oracle.com/middleware/1212/wls/WLDTR/fmw_templates.htm#sthref64 https://blogs.oracle.com/imc/entry/the_specifics_of_adf_12c Note: you should have properly configured Node Manager utility for managing OHS instances Let’s consider configuration process step by step: 1. Shut down all Weblogic instances of existing domain including Admin Server; 2. Install Oracle HTTP Server. You should use your Fusion Middleware Home Path (e.g. /u01/Oracle/FMW12) for Installation Location and select Colocated HTTP Server option as Installation Type. I will not focus on this topic in this post. All information related to OHS installation you could find here: http://docs.oracle.com/middleware/1212/webtier/WTINS/install_gui.htm#i1082009 3. Next we need to extend our existing domain with OHS component. In order to do this you should do the following: a. Run Fusion Middleware Configuration Wizard (ORACLE_HOME/oracle_common/common/bin/config.sh); b. On the step 1 select Update an existing domain option and point your Fusion Middleware Home Path; c. On the step 2 check Oracle HTTP Server, Oracle Enterprise Manager Plugin for WEBTIER templates; d. Go through other steps without any changes and finish configuration process. 4. Start Admin Server and all managed servers related to your cluster 5. Log in to Enterprise Manager FMW Control using http://<hostname>:<port>/em URL 6. Now we will create OHS instance within our Weblogic Domain Infrastructure. Navigate to Weblogic Domain -> Administration -> Create/Delete OHS menu item; 7. Enter to edit mode, clicking Changes -> Lock&Edit menu item; 8. Create new OHS instance clicking Create button; 9. Define Instance Name (e.g. DevOSH) and Machine parameters; 10. Now we need to define listen port. By default OHS will use 7777 port number for income HTTP requests. We could change it to any free port number we would like to use. In order to do it, right click on our created OHS instance (left hand panel) and navigate to Administration -> Port Configuration; 11. Click on record with port number 7777 and then click Edit button; 12. Change port number value (in our case this will be 8080) and then click OK button; 13. Now we need to edit mod_wl_ohs configuration in order to enable OHS to act as proxy for WebLogic Server Instances/Cluster; 14. In order to do it right click on our created OHS instance (left panel) and navigate to Administration -> mod_wl_ohs Configuration; a. In Weblogic Cluster you should enter cluster address (define <host:port> for all managed servers which participated in cluster), e.g: 192.168.56.2:7004,192.168.56.2:7005 b. Define Weblogic Port parameter at which the Oracle WebLogic Server host is listening for connection requests from the module (or from other servers); c. Check Dynamic Server List option. This will dynamically update cluster list for every request; d. In the Location table define list of endpoint locations which you would like to process. In order to do this click Add Row button and define Location, Weblogic Cluster, Path Trim and Path Prefix parameters (if required); e. Click Apply button in order to save changes. 15. Activate changes clicking Changes ? Activate Changes menu item; 16. Finally we will start configured OHS instance. Right click on OHS instance tree item under Web Tier folder, select Control -> Start Up menu item; 17. Ensure that OHS instance up and running and then test your environment. Run deployed application to your Weblogic Cluster accessing via OHS web proxy; Normal 0 false false false RU X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi; mso-fareast-language:EN-US;}

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• Cocoa Basic HTTP Authentication : Advice Needed..

  - by Kristiaan

  Hello all, im looking to read the contents of a webpage that is secured with a user name and password. this is a mac OS X application NOT an iphone app so most of the things i have read on here or been suggested to read do not seem to work. Also i am a total beginner with Xcode and Obj C i was told to have a look at a website that provided sample code to http auth however so far i have had little luck in getting this working. below is the main code for the button press in my application, there is also another unit called Base64 below that has some code in i had to change to even get it compiling (no idea if what i changed is correct mind you). NSURL *url = [NSURL URLWithString:@"my URL"]; NSString *userName = @"UN"; NSString *password = @"PW"; NSError *myError = nil; // create a plaintext string in the format username:password NSMutableString *loginString = (NSMutableString*)[@"" stringByAppendingFormat:@"%@:%@", userName, password]; // employ the Base64 encoding above to encode the authentication tokens char *encodedLoginData = [base64 encode:[loginString dataUsingEncoding:NSUTF8StringEncoding]]; // create the contents of the header NSString *authHeader = [@"Basic " stringByAppendingFormat:@"%@", [NSString stringWithCString:encodedLoginData length:strlen(encodedLoginData)]]; //NSString *authHeader = [@"Basic " stringByAppendingFormat:@"%@", loginString];//[NSString stringWithString:loginString length:strlen(loginString)]]; NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL: url cachePolicy: NSURLRequestReloadIgnoringCacheData timeoutInterval: 3]; // add the header to the request. Here's the $$$!!! [request addValue:authHeader forHTTPHeaderField:@"Authorization"]; // perform the reqeust NSURLResponse *response; NSData *data = [NSURLConnection sendSynchronousRequest: request returningResponse: &response error: &myError]; //*error = myError; // POW, here's the content of the webserver's response. NSString *result = [NSString stringWithCString:[data bytes] length:[data length]]; [myTextView setString:result]; code from the BASE64 file #import "base64.h" static char *alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+-"; @implementation Base64 +(char *)encode:(NSData *)plainText { // create an adequately sized buffer for the output. every 3 bytes // become four basically with padding to the next largest integer // divisible by four. char * encodedText = malloc((((([plainText length] % 3) + [plainText length]) / 3) * 4) + 1); char* inputBuffer = malloc([plainText length]); inputBuffer = (char *)[plainText bytes]; int i; int j = 0; // encode, this expands every 3 bytes to 4 for(i = 0; i < [plainText length]; i += 3) { encodedText[j++] = alphabet[(inputBuffer[i] & 0xFC) >> 2]; encodedText[j++] = alphabet[((inputBuffer[i] & 0x03) << 4) | ((inputBuffer[i + 1] & 0xF0) >> 4)]; if(i + 1 >= [plainText length]) // padding encodedText[j++] = '='; else encodedText[j++] = alphabet[((inputBuffer[i + 1] & 0x0F) << 2) | ((inputBuffer[i + 2] & 0xC0) >> 6)]; if(i + 2 >= [plainText length]) // padding encodedText[j++] = '='; else encodedText[j++] = alphabet[inputBuffer[i + 2] & 0x3F]; } // terminate the string encodedText[j] = 0; return encodedText;//outputBuffer; } @end when executing the code it stops on the following line with a EXC_BAD_ACCESS ?!?!? NSString *authHeader = [@"Basic " stringByAppendingFormat:@"%@", [NSString stringWithCString:encodedLoginData length:strlen(encodedLoginData)]]; any help would be appreciated as i am a little clueless on this problem, not being very literate with Cocoa, objective c, xcode is only adding fuel to this fire for me.

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• Custom webserver caching

  - by Mark Kinsella

  I'm working with a custom webserver on an embedded system and having some problems correctly setting my HTTP Headers for caching. Our webserver is generating all dynamic content as XML and we're using semi-static XSL files to display it with some dynamic JSON requests thrown in for good measure along with semi-static images. I say "semi-static" because the problems occur when we need to do a firmware update which might change the XSL and image files. Here's what needs to be done: cache the XSL and image files and do not cache the XML and JSON responses. I have full control over the HTTP response and am currently: Using ETags with the XSL and image files, using the modified time and size to generate the ETag Setting Cache-Control: no-cache on the XML and JSON responses As I said, everything works dandy until a firmware update when the XSL and image files are sometimes cached. I've seen it work fine with the latest versions of Firefox and Safari but have had some problems with IE. I know one solution to this problem would be simply rename the XSL and image files after each version (eg. logo-v1.1.png, logo-v1.2.png) and set the Expires header to a date in the future but this would be difficult with the XSL files and I'd like to avoid this. Note: There is a clock on the unit but requires the user to set it and might not be 100% reliable which is what might be causing my caching issues when using ETags. What's the best practice that I should employ? I'd like to avoid as many webserver requests as possible but invalidating old XSL and image files after a software update is the #1 priority.

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• Email Tracking - GMail

  - by Abs

  Hello all, I am creating my own email tracking system for email marketing tracking. I have been able to determine each persons email client they are using by using the http referrer but for some reason GMAIL does not send a HTTP_REFERRER at all! So I am trying to find another way of identifying when gmail requests a transparent image from my server. I get the following headers print_r($_SERVER);: DOCUMENT_ROOT = /usr/local/apache/htdocs GATEWAY_INTERFACE = CGI/1.1 HTTP_ACCEPT = */* HTTP_ACCEPT_CHARSET = ISO-8859-1,utf-8;q=0.7,*;q=0.3 HTTP_ACCEPT_ENCODING = gzip,deflate,sdch HTTP_ACCEPT_LANGUAGE = en-GB,en-US;q=0.8,en;q=0.6 HTTP_CONNECTION = keep-alive HTTP_COOKIE = __utmz=156230011.1290976484.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none); __utma=156230011.422791272.1290976484.1293034866.1293050468.7 HTTP_HOST = xx.xxx.xx.xxx HTTP_USER_AGENT = Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.10 (KHTML, like Gecko) Chrome/8.0.552.237 Safari/534.10 PATH = /bin:/usr/bin QUERY_STRING = i=MTA= REDIRECT_STATUS = 200 REMOTE_ADDR = xx.xxx.xx.xxx REMOTE_PORT = 61296 REQUEST_METHOD = GET Is there anything of use in that list? Or is there something else I can do to actually get the http referrer, if not how are other ESPs managing to find whether gmail was used to view an email? Btw, I appreciate it if we can hold back on whether this is ethical or not as many ESPs do this already, I just don't want to pay for their service and I want to do it internally. Thanks all for any implementation advice. Update Just thought I would update this question and make it clearer in light of the bounty. I would like to find out when a user opens my email when sent to a GMail inbox. Assume, I have the usual transparent image tracking and the user does not block images. I would like to do this with the single request and the header details I get when the transparent image is requested.

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• How do I handle a POST request in Perl and FastCGI?

  - by Peterim

  Unfortunately, I'm not familiar with Perl, so asking here. Actually I'm using FCGI with Perl. I need to 1. accept a POST request - 2. send it via POST to another url - 3. get results - 4. return results to the first POST request (4 steps). To accept a POST request (step 1) I use the following code (found it somewhere in the Internet): $ENV{'REQUEST_METHOD'} =~ tr/a-z/A-Z/; if ($ENV{'REQUEST_METHOD'} eq "POST") { read(STDIN, $buffer, $ENV{'CONTENT_LENGTH'}); } else { print ("some error"); } @pairs = split(/&/, $buffer); foreach $pair (@pairs) { ($name, $value) = split(/=/, $pair); $value =~ tr/+/ /; $value =~ s/%(..)/pack("C", hex($1))/eg; $FORM{$name} = $value; } The content of $name (it's a string) is the result of the first step. Now I need to send $name via POST request to some_url (step 2) which returns me another result (step 3), which I have to return as a result to the very first POST request (step 4). Any help with this would be greatly appreciated. Thank you.

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• RESTful httpclient for Ant

  - by kjetildm

  I need a RESTful httpclient for Ant. None of the contrib related tasks seem to work anymore.. Hasn't anyone bridged Commons-HTTPClient and Ant yet?

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• http_post_data adding extra characters in response

  - by Siyam

  Hey Guys I am getting some extra characters like '5ae' and '45c' interspersed along with valid data when using http_post_data. The data I am sending is XML and so is the response. The response contains these weird characters thats making the XML invalid. If I use fsockopen I do not have this issue. Would really like some input on this.

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• The HTTP verb POST used to access path '[my path]' is not allowed.

  - by Jed

  I am receiving an error that states: "The HTTP verb POST used to access path '[my path]' is not allowed.". The error is being caused by the fact that I am implementing an HTML form element that uses the POST method and does not explicitly define an .aspx page in its ACTION parameter. For example: <form action="" method="post"> <input type="submit" /> </form> The HTML above is on a file at "/foo/default.aspx". Now, if the user points the URL to the root directory "foo" without specifying the aspx file (i.e. "http://localhost/foo") and then submits the form, the error "The HTTP verb POST used to access path '/foo' is not allowed." will be thrown. However, if the user goes to "http://localhost/foo/default.aspx" and then submits the form, all goes well (even if the ACTION parameter is left empty). Note: If I explicitly add the name of the .aspx (default.aspx) page to the ACTION parameter, no errors are thrown. So the example below works fine regardless if the user defines the name of the file in the URL or not. <form action="default.aspx" method="post"> <input type="submit" /> </form> I was curious as to why the error was being thrown, so I read a Microsoft KB that states This problem occurs because a client makes an HTTP request by sending the POST method to a static HTML page. Static HTML pages do not support the POST method. I suppose the core of the explanation makes sense, however in my case, my form is not being sent to a static html page - it's being sent to the same page that the html form lives on (default.aspx)... this is implicit to an ACTION param that is left empty. Is it possible to configure IIS (or otherwise) that will allow us to do form POSTing and keep the ACTION param empty?

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• iPhone 4S Post Paid Rental Plans From Airtel & Aircel [India]

  - by Gopinath

  Apple iPhone 4S is available from Airtel and Aircel cellular operators with mind blowing price tags close to Rs. 50,000/-. If you are a fan boy and ready to buy iPhone 4S here are the details of monthly tariffs offered by Airtel & Aircel. Airtel iPhone 4S Post Paid Plans Airtel has a range of post plans for iPhone 4S lovers. Irrespective of the model of iPhone 4S you are planning to buy they offer post paid plans starting from Rs. 300 per month(after 50% discount on original rental of Rs.600 ) with 200 MB free 3G data to Rs. 1000 with 3072 MB free 3G data. The following table runs down complete details of various plans in offer. For pre-paid iPhone 4S tariffs please check this iPhone 4S Airtel website Aircel iPhone 4S Post Paid Plans Aircel has an unique plan for it’s iPhone 4S customers depending on the model they are willing to buy. For some reason the post paid plans are closely tied with the model of the phone and I believe this is not the right thing for its customers. The plan for 16 GB model costs Rs. 900 for 32 GB model that monthly plan costs Rs. 1150.  Like Airtel these monthly rentals are after 50% discount. This article titled,iPhone 4S Post Paid Rental Plans From Airtel & Aircel [India], was originally published at Tech Dreams. Grab our rss feed or fan us on Facebook to get updates from us.

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• A Taxonomy of Numerical Methods v1

  - by JoshReuben

  Numerical Analysis – When, What, (but not how) Once you understand the Math & know C++, Numerical Methods are basically blocks of iterative & conditional math code. I found the real trick was seeing the forest for the trees – knowing which method to use for which situation. Its pretty easy to get lost in the details – so I’ve tried to organize these methods in a way that I can quickly look this up. I’ve included links to detailed explanations and to C++ code examples. I’ve tried to classify Numerical methods in the following broad categories: Solving Systems of Linear Equations Solving Non-Linear Equations Iteratively Interpolation Curve Fitting Optimization Numerical Differentiation & Integration Solving ODEs Boundary Problems Solving EigenValue problems Enjoy – I did ! Solving Systems of Linear Equations Overview Solve sets of algebraic equations with x unknowns The set is commonly in matrix form Gauss-Jordan Elimination http://en.wikipedia.org/wiki/Gauss%E2%80%93Jordan_elimination C++: http://www.codekeep.net/snippets/623f1923-e03c-4636-8c92-c9dc7aa0d3c0.aspx Produces solution of the equations & the coefficient matrix Efficient, stable 2 steps: · Forward Elimination – matrix decomposition: reduce set to triangular form (0s below the diagonal) or row echelon form. If degenerate, then there is no solution · Backward Elimination –write the original matrix as the product of ints inverse matrix & its reduced row-echelon matrix à reduce set to row canonical form & use back-substitution to find the solution to the set Elementary ops for matrix decomposition: · Row multiplication · Row switching · Add multiples of rows to other rows Use pivoting to ensure rows are ordered for achieving triangular form LU Decomposition http://en.wikipedia.org/wiki/LU_decomposition C++: http://ganeshtiwaridotcomdotnp.blogspot.co.il/2009/12/c-c-code-lu-decomposition-for-solving.html Represent the matrix as a product of lower & upper triangular matrices A modified version of GJ Elimination Advantage – can easily apply forward & backward elimination to solve triangular matrices Techniques: · Doolittle Method – sets the L matrix diagonal to unity · Crout Method - sets the U matrix diagonal to unity Note: both the L & U matrices share the same unity diagonal & can be stored compactly in the same matrix Gauss-Seidel Iteration http://en.wikipedia.org/wiki/Gauss%E2%80%93Seidel_method C++: http://www.nr.com/forum/showthread.php?t=722 Transform the linear set of equations into a single equation & then use numerical integration (as integration formulas have Sums, it is implemented iteratively). an optimization of Gauss-Jacobi: 1.5 times faster, requires 0.25 iterations to achieve the same tolerance Solving Non-Linear Equations Iteratively find roots of polynomials – there may be 0, 1 or n solutions for an n order polynomial use iterative techniques Iterative methods · used when there are no known analytical techniques · Requires set functions to be continuous & differentiable · Requires an initial seed value – choice is critical to convergence à conduct multiple runs with different starting points & then select best result · Systematic - iterate until diminishing returns, tolerance or max iteration conditions are met · bracketing techniques will always yield convergent solutions, non-bracketing methods may fail to converge Incremental method if a nonlinear function has opposite signs at 2 ends of a small interval x1 & x2, then there is likely to be a solution in their interval – solutions are detected by evaluating a function over interval steps, for a change in sign, adjusting the step size dynamically. Limitations – can miss closely spaced solutions in large intervals, cannot detect degenerate (coinciding) solutions, limited to functions that cross the x-axis, gives false positives for singularities Fixed point method http://en.wikipedia.org/wiki/Fixed-point_iteration C++: http://books.google.co.il/books?id=weYj75E_t6MC&pg=PA79&lpg=PA79&dq=fixed+point+method++c%2B%2B&source=bl&ots=LQ-5P_taoC&sig=lENUUIYBK53tZtTwNfHLy5PEWDk&hl=en&sa=X&ei=wezDUPW1J5DptQaMsIHQCw&redir_esc=y#v=onepage&q=fixed%20point%20method%20%20c%2B%2B&f=false Algebraically rearrange a solution to isolate a variable then apply incremental method Bisection method http://en.wikipedia.org/wiki/Bisection_method C++: http://numericalcomputing.wordpress.com/category/algorithms/ Bracketed - Select an initial interval, keep bisecting it ad midpoint into sub-intervals and then apply incremental method on smaller & smaller intervals – zoom in Adv: unaffected by function gradient à reliable Disadv: slow convergence False Position Method http://en.wikipedia.org/wiki/False_position_method C++: http://www.dreamincode.net/forums/topic/126100-bisection-and-false-position-methods/ Bracketed - Select an initial interval , & use the relative value of function at interval end points to select next sub-intervals (estimate how far between the end points the solution might be & subdivide based on this) Newton-Raphson method http://en.wikipedia.org/wiki/Newton's_method C++: http://www-users.cselabs.umn.edu/classes/Summer-2012/csci1113/index.php?page=./newt3 Also known as Newton's method Convenient, efficient Not bracketed – only a single initial guess is required to start iteration – requires an analytical expression for the first derivative of the function as input. Evaluates the function & its derivative at each step. Can be extended to the Newton MutiRoot method for solving multiple roots Can be easily applied to an of n-coupled set of non-linear equations – conduct a Taylor Series expansion of a function, dropping terms of order n, rewrite as a Jacobian matrix of PDs & convert to simultaneous linear equations !!! Secant Method http://en.wikipedia.org/wiki/Secant_method C++: http://forum.vcoderz.com/showthread.php?p=205230 Unlike N-R, can estimate first derivative from an initial interval (does not require root to be bracketed) instead of inputting it Since derivative is approximated, may converge slower. Is fast in practice as it does not have to evaluate the derivative at each step. Similar implementation to False Positive method Birge-Vieta Method http://mat.iitm.ac.in/home/sryedida/public_html/caimna/transcendental/polynomial%20methods/bv%20method.html C++: http://books.google.co.il/books?id=cL1boM2uyQwC&pg=SA3-PA51&lpg=SA3-PA51&dq=Birge-Vieta+Method+c%2B%2B&source=bl&ots=QZmnDTK3rC&sig=BPNcHHbpR_DKVoZXrLi4nVXD-gg&hl=en&sa=X&ei=R-_DUK2iNIjzsgbE5ID4Dg&redir_esc=y#v=onepage&q=Birge-Vieta%20Method%20c%2B%2B&f=false combines Horner's method of polynomial evaluation (transforming into lesser degree polynomials that are more computationally efficient to process) with Newton-Raphson to provide a computational speed-up Interpolation Overview Construct new data points for as close as possible fit within range of a discrete set of known points (that were obtained via sampling, experimentation) Use Taylor Series Expansion of a function f(x) around a specific value for x Linear Interpolation http://en.wikipedia.org/wiki/Linear_interpolation C++: http://www.hamaluik.com/?p=289 Straight line between 2 points à concatenate interpolants between each pair of data points Bilinear Interpolation http://en.wikipedia.org/wiki/Bilinear_interpolation C++: http://supercomputingblog.com/graphics/coding-bilinear-interpolation/2/ Extension of the linear function for interpolating functions of 2 variables – perform linear interpolation first in 1 direction, then in another. Used in image processing – e.g. texture mapping filter. Uses 4 vertices to interpolate a value within a unit cell. Lagrange Interpolation http://en.wikipedia.org/wiki/Lagrange_polynomial C++: http://www.codecogs.com/code/maths/approximation/interpolation/lagrange.php For polynomials Requires recomputation for all terms for each distinct x value – can only be applied for small number of nodes Numerically unstable Barycentric Interpolation http://epubs.siam.org/doi/pdf/10.1137/S0036144502417715 C++: http://www.gamedev.net/topic/621445-barycentric-coordinates-c-code-check/ Rearrange the terms in the equation of the Legrange interpolation by defining weight functions that are independent of the interpolated value of x Newton Divided Difference Interpolation http://en.wikipedia.org/wiki/Newton_polynomial C++: http://jee-appy.blogspot.co.il/2011/12/newton-divided-difference-interpolation.html Hermite Divided Differences: Interpolation polynomial approximation for a given set of data points in the NR form - divided differences are used to approximately calculate the various differences. For a given set of 3 data points , fit a quadratic interpolant through the data Bracketed functions allow Newton divided differences to be calculated recursively Difference table Cubic Spline Interpolation http://en.wikipedia.org/wiki/Spline_interpolation C++: https://www.marcusbannerman.co.uk/index.php/home/latestarticles/42-articles/96-cubic-spline-class.html Spline is a piecewise polynomial Provides smoothness – for interpolations with significantly varying data Use weighted coefficients to bend the function to be smooth & its 1st & 2nd derivatives are continuous through the edge points in the interval Curve Fitting A generalization of interpolating whereby given data points may contain noise à the curve does not necessarily pass through all the points Least Squares Fit http://en.wikipedia.org/wiki/Least_squares C++: http://www.ccas.ru/mmes/educat/lab04k/02/least-squares.c Residual – difference between observed value & expected value Model function is often chosen as a linear combination of the specified functions Determines: A) The model instance in which the sum of squared residuals has the least value B) param values for which model best fits data Straight Line Fit Linear correlation between independent variable and dependent variable Linear Regression http://en.wikipedia.org/wiki/Linear_regression C++: http://www.oocities.org/david_swaim/cpp/linregc.htm Special case of statistically exact extrapolation Leverage least squares Given a basis function, the sum of the residuals is determined and the corresponding gradient equation is expressed as a set of normal linear equations in matrix form that can be solved (e.g. using LU Decomposition) Can be weighted - Drop the assumption that all errors have the same significance –-> confidence of accuracy is different for each data point. Fit the function closer to points with higher weights Polynomial Fit - use a polynomial basis function Moving Average http://en.wikipedia.org/wiki/Moving_average C++: http://www.codeproject.com/Articles/17860/A-Simple-Moving-Average-Algorithm Used for smoothing (cancel fluctuations to highlight longer-term trends & cycles), time series data analysis, signal processing filters Replace each data point with average of neighbors. Can be simple (SMA), weighted (WMA), exponential (EMA). Lags behind latest data points – extra weight can be given to more recent data points. Weights can decrease arithmetically or exponentially according to distance from point. Parameters: smoothing factor, period, weight basis Optimization Overview Given function with multiple variables, find Min (or max by minimizing –f(x)) Iterative approach Efficient, but not necessarily reliable Conditions: noisy data, constraints, non-linear models Detection via sign of first derivative - Derivative of saddle points will be 0 Local minima Bisection method Similar method for finding a root for a non-linear equation Start with an interval that contains a minimum Golden Search method http://en.wikipedia.org/wiki/Golden_section_search C++: http://www.codecogs.com/code/maths/optimization/golden.php Bisect intervals according to golden ratio 0.618.. Achieves reduction by evaluating a single function instead of 2 Newton-Raphson Method Brent method http://en.wikipedia.org/wiki/Brent's_method C++: http://people.sc.fsu.edu/~jburkardt/cpp_src/brent/brent.cpp Based on quadratic or parabolic interpolation – if the function is smooth & parabolic near to the minimum, then a parabola fitted through any 3 points should approximate the minima – fails when the 3 points are collinear , in which case the denominator is 0 Simplex Method http://en.wikipedia.org/wiki/Simplex_algorithm C++: http://www.codeguru.com/cpp/article.php/c17505/Simplex-Optimization-Algorithm-and-Implemetation-in-C-Programming.htm Find the global minima of any multi-variable function Direct search – no derivatives required At each step it maintains a non-degenerative simplex – a convex hull of n+1 vertices. Obtains the minimum for a function with n variables by evaluating the function at n-1 points, iteratively replacing the point of worst result with the point of best result, shrinking the multidimensional simplex around the best point. Point replacement involves expanding & contracting the simplex near the worst value point to determine a better replacement point Oscillation can be avoided by choosing the 2nd worst result Restart if it gets stuck Parameters: contraction & expansion factors Simulated Annealing http://en.wikipedia.org/wiki/Simulated_annealing C++: http://code.google.com/p/cppsimulatedannealing/ Analogy to heating & cooling metal to strengthen its structure Stochastic method – apply random permutation search for global minima - Avoid entrapment in local minima via hill climbing Heating schedule - Annealing schedule params: temperature, iterations at each temp, temperature delta Cooling schedule – can be linear, step-wise or exponential Differential Evolution http://en.wikipedia.org/wiki/Differential_evolution C++: http://www.amichel.com/de/doc/html/ More advanced stochastic methods analogous to biological processes: Genetic algorithms, evolution strategies Parallel direct search method against multiple discrete or continuous variables Initial population of variable vectors chosen randomly – if weighted difference vector of 2 vectors yields a lower objective function value then it replaces the comparison vector Many params: #parents, #variables, step size, crossover constant etc Convergence is slow – many more function evaluations than simulated annealing Numerical Differentiation Overview 2 approaches to finite difference methods: · A) approximate function via polynomial interpolation then differentiate · B) Taylor series approximation – additionally provides error estimate Finite Difference methods http://en.wikipedia.org/wiki/Finite_difference_method C++: http://www.wpi.edu/Pubs/ETD/Available/etd-051807-164436/unrestricted/EAMPADU.pdf Find differences between high order derivative values - Approximate differential equations by finite differences at evenly spaced data points Based on forward & backward Taylor series expansion of f(x) about x plus or minus multiples of delta h. Forward / backward difference - the sums of the series contains even derivatives and the difference of the series contains odd derivatives – coupled equations that can be solved. Provide an approximation of the derivative within a O(h^2) accuracy There is also central difference & extended central difference which has a O(h^4) accuracy Richardson Extrapolation http://en.wikipedia.org/wiki/Richardson_extrapolation C++: http://mathscoding.blogspot.co.il/2012/02/introduction-richardson-extrapolation.html A sequence acceleration method applied to finite differences Fast convergence, high accuracy O(h^4) Derivatives via Interpolation Cannot apply Finite Difference method to discrete data points at uneven intervals – so need to approximate the derivative of f(x) using the derivative of the interpolant via 3 point Lagrange Interpolation Note: the higher the order of the derivative, the lower the approximation precision Numerical Integration Estimate finite & infinite integrals of functions More accurate procedure than numerical differentiation Use when it is not possible to obtain an integral of a function analytically or when the function is not given, only the data points are Newton Cotes Methods http://en.wikipedia.org/wiki/Newton%E2%80%93Cotes_formulas C++: http://www.siafoo.net/snippet/324 For equally spaced data points Computationally easy – based on local interpolation of n rectangular strip areas that is piecewise fitted to a polynomial to get the sum total area Evaluate the integrand at n+1 evenly spaced points – approximate definite integral by Sum Weights are derived from Lagrange Basis polynomials Leverage Trapezoidal Rule for default 2nd formulas, Simpson 1/3 Rule for substituting 3 point formulas, Simpson 3/8 Rule for 4 point formulas. For 4 point formulas use Bodes Rule. Higher orders obtain more accurate results Trapezoidal Rule uses simple area, Simpsons Rule replaces the integrand f(x) with a quadratic polynomial p(x) that uses the same values as f(x) for its end points, but adds a midpoint Romberg Integration http://en.wikipedia.org/wiki/Romberg's_method C++: http://code.google.com/p/romberg-integration/downloads/detail?name=romberg.cpp&can=2&q= Combines trapezoidal rule with Richardson Extrapolation Evaluates the integrand at equally spaced points The integrand must have continuous derivatives Each R(n,m) extrapolation uses a higher order integrand polynomial replacement rule (zeroth starts with trapezoidal) à a lower triangular matrix set of equation coefficients where the bottom right term has the most accurate approximation. The process continues until the difference between 2 successive diagonal terms becomes sufficiently small. Gaussian Quadrature http://en.wikipedia.org/wiki/Gaussian_quadrature C++: http://www.alglib.net/integration/gaussianquadratures.php Data points are chosen to yield best possible accuracy – requires fewer evaluations Ability to handle singularities, functions that are difficult to evaluate The integrand can include a weighting function determined by a set of orthogonal polynomials. Points & weights are selected so that the integrand yields the exact integral if f(x) is a polynomial of degree <= 2n+1 Techniques (basically different weighting functions): · Gauss-Legendre Integration w(x)=1 · Gauss-Laguerre Integration w(x)=e^-x · Gauss-Hermite Integration w(x)=e^-x^2 · Gauss-Chebyshev Integration w(x)= 1 / Sqrt(1-x^2) Solving ODEs Use when high order differential equations cannot be solved analytically Evaluated under boundary conditions RK for systems – a high order differential equation can always be transformed into a coupled first order system of equations Euler method http://en.wikipedia.org/wiki/Euler_method C++: http://rosettacode.org/wiki/Euler_method First order Runge–Kutta method. Simple recursive method – given an initial value, calculate derivative deltas. Unstable & not very accurate (O(h) error) – not used in practice A first-order method - the local error (truncation error per step) is proportional to the square of the step size, and the global error (error at a given time) is proportional to the step size In evolving solution between data points xn & xn+1, only evaluates derivatives at beginning of interval xn à asymmetric at boundaries Higher order Runge Kutta http://en.wikipedia.org/wiki/Runge%E2%80%93Kutta_methods C++: http://www.dreamincode.net/code/snippet1441.htm 2nd & 4th order RK - Introduces parameterized midpoints for more symmetric solutions à accuracy at higher computational cost Adaptive RK – RK-Fehlberg – estimate the truncation at each integration step & automatically adjust the step size to keep error within prescribed limits. At each step 2 approximations are compared – if in disagreement to a specific accuracy, the step size is reduced Boundary Value Problems Where solution of differential equations are located at 2 different values of the independent variable x à more difficult, because cannot just start at point of initial value – there may not be enough starting conditions available at the end points to produce a unique solution An n-order equation will require n boundary conditions – need to determine the missing n-1 conditions which cause the given conditions at the other boundary to be satisfied Shooting Method http://en.wikipedia.org/wiki/Shooting_method C++: http://ganeshtiwaridotcomdotnp.blogspot.co.il/2009/12/c-c-code-shooting-method-for-solving.html Iteratively guess the missing values for one end & integrate, then inspect the discrepancy with the boundary values of the other end to adjust the estimate Given the starting boundary values u1 & u2 which contain the root u, solve u given the false position method (solving the differential equation as an initial value problem via 4th order RK), then use u to solve the differential equations. Finite Difference Method For linear & non-linear systems Higher order derivatives require more computational steps – some combinations for boundary conditions may not work though Improve the accuracy by increasing the number of mesh points Solving EigenValue Problems An eigenvalue can substitute a matrix when doing matrix multiplication à convert matrix multiplication into a polynomial EigenValue For a given set of equations in matrix form, determine what are the solution eigenvalue & eigenvectors Similar Matrices - have same eigenvalues. Use orthogonal similarity transforms to reduce a matrix to diagonal form from which eigenvalue(s) & eigenvectors can be computed iteratively Jacobi method http://en.wikipedia.org/wiki/Jacobi_method C++: http://people.sc.fsu.edu/~jburkardt/classes/acs2_2008/openmp/jacobi/jacobi.html Robust but Computationally intense – use for small matrices < 10x10 Power Iteration http://en.wikipedia.org/wiki/Power_iteration For any given real symmetric matrix, generate the largest single eigenvalue & its eigenvectors Simplest method – does not compute matrix decomposition à suitable for large, sparse matrices Inverse Iteration Variation of power iteration method – generates the smallest eigenvalue from the inverse matrix Rayleigh Method http://en.wikipedia.org/wiki/Rayleigh's_method_of_dimensional_analysis Variation of power iteration method Rayleigh Quotient Method Variation of inverse iteration method Matrix Tri-diagonalization Method Use householder algorithm to reduce an NxN symmetric matrix to a tridiagonal real symmetric matrix vua N-2 orthogonal transforms     Whats Next Outside of Numerical Methods there are lots of different types of algorithms that I’ve learned over the decades: Data Mining – (I covered this briefly in a previous post: http://geekswithblogs.net/JoshReuben/archive/2007/12/31/ssas-dm-algorithms.aspx ) Search & Sort Routing Problem Solving Logical Theorem Proving Planning Probabilistic Reasoning Machine Learning Solvers (eg MIP) Bioinformatics (Sequence Alignment, Protein Folding) Quant Finance (I read Wilmott’s books – interesting) Sooner or later, I’ll cover the above topics as well.

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• How do I get the HTML status code with jQuery?

  - by cvack

  I want to check if a page returns the status code 401. Is this possible? Here is my try, but it only returns 0. $.ajax({ url: "http://my-ip/test/test.php", data: {}, complete: function(xhr, statusText){ alert(xhr.status); } });

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• Trying to update debian not working

  - by Sean

  As root i type this command apt-get update and get these error messages. > Err http://security.debian.org lenny/updates Release.gpg Could not resolve 'security.debian.org' Err http://security.debian.org lenny/updates/main Translation-en_US Could not resolve 'security.debian.org' Err http://security.debian.org lenny/updates/contrib Translation-en_US Could not resolve 'security.debian.org' Err http://security.debian.org lenny/updates/non-free Translation-en_US Could not resolve 'security.debian.org' Err http://www.backports.org lenny-backports Release.gpg Could not resolve 'www.backports.org' Err http://www.backports.org lenny-backports/main Translation-en_US Could not resolve 'www.backports.org' Err http://www.backports.org lenny-backports/contrib Translation-en_US Could not resolve 'www.backports.org' Err http://www.backports.org lenny-backports/non-free Translation-en_US Could not resolve 'www.backports.org' Err http://ftp.us.debian.org lenny Release.gpg Could not resolve 'ftp.us.debian.org' Err http://ftp.us.debian.org lenny/main Translation-en_US Could not resolve 'ftp.us.debian.org' Err http://ftp.us.debian.org lenny/contrib Translation-en_US Could not resolve 'ftp.us.debian.org' Err http://ftp.us.debian.org lenny/non-free Translation-en_US Could not resolve 'ftp.us.debian.org' Err http://http.us.debian.org stable Release.gpg Could not resolve 'http.us.debian.org' Err http://http.us.debian.org stable/main Translation-en_US Could not resolve 'http.us.debian.org' Err http://http.us.debian.org stable/contrib Translation-en_US Could not resolve 'http.us.debian.org' Err http://http.us.debian.org stable/non-free Translation-en_US Could not resolve 'http.us.debian.org' Reading package lists... Done W: Failed to fetch http://ftp.us.debian.org/debian/dists/lenny/Release.gpg Could not resolve 'ftp.us.debian.org' W: Failed to fetch http://ftp.us.debian.org/debian/dists/lenny/main/i18n/Translation-en_US.gz Could not resolve 'ftp.us.debian.org' W: Failed to fetch http://ftp.us.debian.org/debian/dists/lenny/contrib/i18n/Translation-en_US.gz Could not resolve 'ftp.us.debian.org' W: Failed to fetch http://ftp.us.debian.org/debian/dists/lenny/non-free/i18n/Translation-en_US.gz Could not resolve 'ftp.us.debian.org' W: Failed to fetch http://http.us.debian.org/debian/dists/stable/Release.gpg Could not resolve 'http.us.debian.org' W: Failed to fetch http://http.us.debian.org/debian/dists/stable/main/i18n/Translation-en_US.gz Could not resolve 'http.us.debian.org' W: Failed to fetch http://http.us.debian.org/debian/dists/stable/contrib/i18n/Translation-en_US.gz Could not resolve 'http.us.debian.org' W: Failed to fetch http://http.us.debian.org/debian/dists/stable/non-free/i18n/Translation-en_US.gz Could not resolve 'http.us.debian.org' W: Failed to fetch http://security.debian.org/dists/lenny/updates/Release.gpg Could not resolve 'security.debian.org' W: Failed to fetch http://security.debian.org/dists/lenny/updates/main/i18n/Translation-en_US.gz Could not resolve 'security.debian.org' W: Failed to fetch http://security.debian.org/dists/lenny/updates/contrib/i18n/Translation-en_US.gz Could not resolve 'security.debian.org' W: Failed to fetch http://security.debian.org/dists/lenny/updates/non-free/i18n/Translation-en_US.gz Could not resolve 'security.debian.org' W: Failed to fetch http://www.backports.org/debian/dists/lenny-backports/Release.gpg Could not resolve 'www.backports.org' W: Failed to fetch http://www.backports.org/debian/dists/lenny-backports/main/i18n/Translation-en_US.gz Could not resolve 'www.backports.org' W: Failed to fetch http://www.backports.org/debian/dists/lenny-backports/contrib/i18n/Translation-en_US.gz Could not resolve 'www.backports.org' W: Failed to fetch http://www.backports.org/debian/dists/lenny-backports/non-free/i18n/Translation-en_US.gz Could not resolve 'www.backports.org' W: Some index files failed to download, they have been ignored, or old ones used instead. W: You may want to run apt-get update to correct these problems This is on a dreamplug linux server. Configured so that my network starts on 192.168.1.2 and my router is port forwarding ssh to 192.168.1.6 to the server.

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• Coding With Windows Azure IaaS

  - by Hisham El-bereky

  This post will focus on some advanced programming topics concerned with IaaS (Infrastructure as a Service) which provided as windows azure virtual machine (with its related resources like virtual disk and virtual network), you know that windows azure started as PaaS cloud platform but regarding to some business cases which need to have full control over their virtual machine, so windows azure directed toward providing IaaS. Sometimes you will need to manage your cloud IaaS through code may be for these reasons: Working on hyper-cloud system by providing bursting connector to windows azure virtual machines Providing multi-tenant system which consume windows azure virtual machine Automated process on your on-premises or cloud service which need to utilize some virtual resources We are going to implement the following basic operation using C# code: List images Create virtual machine List virtual machines Restart virtual machine Delete virtual machine Before going to implement the above operations we need to prepare client side and windows azure subscription to communicate correctly by providing management certificate (x.509 v3 certificates) which permit client access to resources in your Windows Azure subscription, whilst requests made using the Windows Azure Service Management REST API require authentication against a certificate that you provide to Windows Azure More info about setting management certificate located here. And to install .cer on other client machine you will need the .pfx file, or if not exist by exporting .cer as .pfx Note: You will need to install .net 4.5 on your machine to try the code So let start This post built on the post sent by Michael Washam "Advanced Windows Azure IaaS – Demo Code", so I'm here to declare some points and to add new operation which is not exist in Michael's demo The basic C# class object used here as client to azure REST API for IaaS service is HttpClient (Provides a base class for sending HTTP requests and receiving HTTP responses from a resource identified by a URI) this object must be initialized with the required data like certificate, headers and content if required. Also I'd like to refer here that the code is based on using Asynchronous programming with calls to azure which enhance the performance and gives us the ability to work with complex calls which depends on more than one sub-call to achieve some operation The following code explain how to get certificate and initializing HttpClient object with required data like headers and content HttpClient GetHttpClient() { X509Store certificateStore = null; X509Certificate2 certificate = null; try { certificateStore = new X509Store(StoreName.My, StoreLocation.CurrentUser); certificateStore.Open(OpenFlags.ReadOnly); string thumbprint = ConfigurationManager.AppSettings["CertThumbprint"]; var certificates = certificateStore.Certificates.Find(X509FindType.FindByThumbprint, thumbprint, false); if (certificates.Count > 0) { certificate = certificates[0]; } } finally { if (certificateStore != null) certificateStore.Close(); }   WebRequestHandler handler = new WebRequestHandler(); if (certificate!= null) { handler.ClientCertificates.Add(certificate); HttpClient httpClient = new HttpClient(handler); //And to set required headers lik x-ms-version httpClient.DefaultRequestHeaders.Add("x-ms-version", "2012-03-01"); httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/xml")); return httpClient; } return null; }  Let us keep the object httpClient as reference object used to call windows azure REST API IaaS service. For each request operation we need to define: Request URI HTTP Method Headers Content body (1) List images The List OS Images operation retrieves a list of the OS images from the image repository Request URI https://management.core.windows.net/<subscription-id>/services/images] Replace <subscription-id> with your windows Id HTTP Method GET (HTTP 1.1) Headers x-ms-version: 2012-03-01 Body None.  C# Code List<String> imageList = new List<String>(); //replace _subscriptionid with your WA subscription String uri = String.Format("https://management.core.windows.net/{0}/services/images", _subscriptionid);  HttpClient http = GetHttpClient(); Stream responseStream = await http.GetStreamAsync(uri);  if (responseStream != null) {      XDocument xml = XDocument.Load(responseStream);      var images = xml.Root.Descendants(ns + "OSImage").Where(i => i.Element(ns + "OS").Value == "Windows");      foreach (var image in images)      {      string img = image.Element(ns + "Name").Value;      imageList.Add(img);      } } More information about the REST call (Request/Response) located here on this link http://msdn.microsoft.com/en-us/library/windowsazure/jj157191.aspx (2) Create Virtual Machine Creating virtual machine required service and deployment to be created first, so creating VM should be done through three steps incase hosted service and deployment is not created yet Create hosted service, a container for service deployments in Windows Azure. A subscription may have zero or more hosted services Create deployment, a service that is running on Windows Azure. A deployment may be running in either the staging or production deployment environment. It may be managed either by referencing its deployment ID, or by referencing the deployment environment in which it's running. Create virtual machine, the previous two steps info required here in this step I suggest here to use the same name for service, deployment and service to make it easy to manage virtual machines Note: A name for the hosted service that is unique within Windows Azure. This name is the DNS prefix name and can be used to access the hosted service. For example: http://ServiceName.cloudapp.net// 2.1 Create service Request URI https://management.core.windows.net/<subscription-id>/services/hostedservices HTTP Method POST (HTTP 1.1) Header x-ms-version: 2012-03-01 Content-Type: application/xml Body More details about request body (and other information) are located here http://msdn.microsoft.com/en-us/library/windowsazure/gg441304.aspx C# code The following method show how to create hosted service async public Task<String> NewAzureCloudService(String ServiceName, String Location, String AffinityGroup, String subscriptionid) { String requestID = String.Empty;   String uri = String.Format("https://management.core.windows.net/{0}/services/hostedservices", subscriptionid); HttpClient http = GetHttpClient();   System.Text.ASCIIEncoding ae = new System.Text.ASCIIEncoding(); byte[] svcNameBytes = ae.GetBytes(ServiceName);   String locationEl = String.Empty; String locationVal = String.Empty;   if (String.IsNullOrEmpty(Location) == false) { locationEl = "Location"; locationVal = Location; } else { locationEl = "AffinityGroup"; locationVal = AffinityGroup; }   XElement srcTree = new XElement("CreateHostedService", new XAttribute(XNamespace.Xmlns + "i", ns1), new XElement("ServiceName", ServiceName), new XElement("Label", Convert.ToBase64String(svcNameBytes)), new XElement(locationEl, locationVal) ); ApplyNamespace(srcTree, ns);   XDocument CSXML = new XDocument(srcTree); HttpContent content = new StringContent(CSXML.ToString()); content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue("application/xml");   HttpResponseMessage responseMsg = await http.PostAsync(uri, content); if (responseMsg != null) { requestID = responseMsg.Headers.GetValues("x-ms-request-id").FirstOrDefault(); } return requestID; } 2.2 Create Deployment Request URI https://management.core.windows.net/<subscription-id>/services/hostedservices/<service-name>/deploymentslots/<deployment-slot-name> <deployment-slot-name> with staging or production, depending on where you wish to deploy your service package <service-name> provided as input from the previous step HTTP Method POST (HTTP 1.1) Header x-ms-version: 2012-03-01 Content-Type: application/xml Body More details about request body (and other information) are located here http://msdn.microsoft.com/en-us/library/windowsazure/ee460813.aspx C# code The following method show how to create hosted service deployment async public Task<String> NewAzureVMDeployment(String ServiceName, String VMName, String VNETName, XDocument VMXML, XDocument DNSXML) { String requestID = String.Empty;     String uri = String.Format("https://management.core.windows.net/{0}/services/hostedservices/{1}/deployments", _subscriptionid, ServiceName); HttpClient http = GetHttpClient(); XElement srcTree = new XElement("Deployment", new XAttribute(XNamespace.Xmlns + "i", ns1), new XElement("Name", ServiceName), new XElement("DeploymentSlot", "Production"), new XElement("Label", ServiceName), new XElement("RoleList", null) );   if (String.IsNullOrEmpty(VNETName) == false) { srcTree.Add(new XElement("VirtualNetworkName", VNETName)); }   if(DNSXML != null) { srcTree.Add(new XElement("DNS", new XElement("DNSServers", DNSXML))); }   XDocument deploymentXML = new XDocument(srcTree); ApplyNamespace(srcTree, ns);   deploymentXML.Descendants(ns + "RoleList").FirstOrDefault().Add(VMXML.Root);     String fixedXML = deploymentXML.ToString().Replace(" xmlns=\"\"", ""); HttpContent content = new StringContent(fixedXML); content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue("application/xml");   HttpResponseMessage responseMsg = await http.PostAsync(uri, content); if (responseMsg != null) { requestID = responseMsg.Headers.GetValues("x-ms-request-id").FirstOrDefault(); }   return requestID; } 2.3 Create Virtual Machine Request URI https://management.core.windows.net/<subscription-id>/services/hostedservices/<cloudservice-name>/deployments/<deployment-name>/roles <cloudservice-name> and <deployment-name> are provided as input from the previous steps Http Method POST (HTTP 1.1) Header x-ms-version: 2012-03-01 Content-Type: application/xml Body More details about request body (and other information) located here http://msdn.microsoft.com/en-us/library/windowsazure/jj157186.aspx C# code async public Task<String> NewAzureVM(String ServiceName, String VMName, XDocument VMXML) { String requestID = String.Empty;   String deployment = await GetAzureDeploymentName(ServiceName);   String uri = String.Format("https://management.core.windows.net/{0}/services/hostedservices/{1}/deployments/{2}/roles", _subscriptionid, ServiceName, deployment);   HttpClient http = GetHttpClient(); HttpContent content = new StringContent(VMXML.ToString()); content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue("application/xml"); HttpResponseMessage responseMsg = await http.PostAsync(uri, content); if (responseMsg != null) { requestID = responseMsg.Headers.GetValues("x-ms-request-id").FirstOrDefault(); } return requestID; } (3) List Virtual Machines To list virtual machine hosted on windows azure subscription we have to loop over all hosted services to get its hosted virtual machines To do that we need to execute the following operations: listing hosted services listing hosted service Virtual machine 3.1 Listing Hosted Services Request URI https://management.core.windows.net/<subscription-id>/services/hostedservices HTTP Method GET (HTTP 1.1) Headers x-ms-version: 2012-03-01 Body None. More info about this HTTP request located here on this link http://msdn.microsoft.com/en-us/library/windowsazure/ee460781.aspx C# Code async private Task<List<XDocument>> GetAzureServices(String subscriptionid) { String uri = String.Format("https://management.core.windows.net/{0}/services/hostedservices ", subscriptionid); List<XDocument> services = new List<XDocument>();   HttpClient http = GetHttpClient();   Stream responseStream = await http.GetStreamAsync(uri);   if (responseStream != null) { XDocument xml = XDocument.Load(responseStream); var svcs = xml.Root.Descendants(ns + "HostedService"); foreach (XElement r in svcs) { XDocument vm = new XDocument(r); services.Add(vm); } }   return services; }  3.2 Listing Hosted Service Virtual Machines Request URI https://management.core.windows.net/<subscription-id>/services/hostedservices/<service-name>/deployments/<deployment-name>/roles/<role-name> HTTP Method GET (HTTP 1.1) Headers x-ms-version: 2012-03-01 Body None. More info about this HTTP request here http://msdn.microsoft.com/en-us/library/windowsazure/jj157193.aspx C# Code async public Task<XDocument> GetAzureVM(String ServiceName, String VMName, String subscriptionid) { String deployment = await GetAzureDeploymentName(ServiceName); XDocument vmXML = new XDocument();   String uri = String.Format("https://management.core.windows.net/{0}/services/hostedservices/{1}/deployments/{2}/roles/{3}", subscriptionid, ServiceName, deployment, VMName);   HttpClient http = GetHttpClient(); Stream responseStream = await http.GetStreamAsync(uri); if (responseStream != null) { vmXML = XDocument.Load(responseStream); }   return vmXML; }  So the final method which can be used to list all virtual machines is: async public Task<XDocument> GetAzureVMs() { List<XDocument> services = await GetAzureServices(); XDocument vms = new XDocument(); vms.Add(new XElement("VirtualMachines")); ApplyNamespace(vms.Root, ns); foreach (var svc in services) { string ServiceName = svc.Root.Element(ns + "ServiceName").Value;   String uri = String.Format("https://management.core.windows.net/{0}/services/hostedservices/{1}/deploymentslots/{2}", _subscriptionid, ServiceName, "Production");   try { HttpClient http = GetHttpClient(); Stream responseStream = await http.GetStreamAsync(uri);   if (responseStream != null) { XDocument xml = XDocument.Load(responseStream); var roles = xml.Root.Descendants(ns + "RoleInstance"); foreach (XElement r in roles) { XElement svcnameel = new XElement("ServiceName", ServiceName); ApplyNamespace(svcnameel, ns); r.Add(svcnameel); // not part of the roleinstance vms.Root.Add(r); } } } catch (HttpRequestException http) { // no vms with cloud service } } return vms; }  (4) Restart Virtual Machine Request URI https://management.core.windows.net/<subscription-id>/services/hostedservices/<service-name>/deployments/<deployment-name>/roles/<role-name>/Operations HTTP Method POST (HTTP 1.1) Headers x-ms-version: 2012-03-01 Content-Type: application/xml Body <RestartRoleOperation xmlns:i="http://www.w3.org/2001/XMLSchema-instance"> <OperationType>RestartRoleOperation</OperationType> </RestartRoleOperation>  More details about this http request here http://msdn.microsoft.com/en-us/library/windowsazure/jj157197.aspx  C# Code async public Task<String> RebootVM(String ServiceName, String RoleName) { String requestID = String.Empty;   String deployment = await GetAzureDeploymentName(ServiceName); String uri = String.Format("https://management.core.windows.net/{0}/services/hostedservices/{1}/deployments/{2}/roleInstances/{3}/Operations", _subscriptionid, ServiceName, deployment, RoleName);   HttpClient http = GetHttpClient();   XElement srcTree = new XElement("RestartRoleOperation", new XAttribute(XNamespace.Xmlns + "i", ns1), new XElement("OperationType", "RestartRoleOperation") ); ApplyNamespace(srcTree, ns);   XDocument CSXML = new XDocument(srcTree); HttpContent content = new StringContent(CSXML.ToString()); content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue("application/xml");   HttpResponseMessage responseMsg = await http.PostAsync(uri, content); if (responseMsg != null) { requestID = responseMsg.Headers.GetValues("x-ms-request-id").FirstOrDefault(); } return requestID; }  (5) Delete Virtual Machine You can delete your hosted virtual machine by deleting its deployment, but I prefer to delete its hosted service also, so you can easily manage your virtual machines from code 5.1 Delete Deployment Request URI https://management.core.windows.net/< subscription-id >/services/hostedservices/< service-name >/deployments/<Deployment-Name> HTTP Method DELETE (HTTP 1.1) Headers x-ms-version: 2012-03-01 Body None. C# code async public Task<HttpResponseMessage> DeleteDeployment( string deploymentName) { string xml = string.Empty; String uri = String.Format("https://management.core.windows.net/{0}/services/hostedservices/{1}/deployments/{2}", _subscriptionid, deploymentName, deploymentName); HttpClient http = GetHttpClient(); HttpResponseMessage responseMessage = await http.DeleteAsync(uri); return responseMessage; }  5.2 Delete Hosted Service Request URI https://management.core.windows.net/<subscription-id>/services/hostedservices/<service-name> HTTP Method DELETE (HTTP 1.1) Headers x-ms-version: 2012-03-01 Body None. C# code async public Task<HttpResponseMessage> DeleteService(string serviceName) { string xml = string.Empty; String uri = String.Format("https://management.core.windows.net/{0}/services/hostedservices/{1}", _subscriptionid, serviceName); Log.Info("Windows Azure URI (http DELETE verb): " + uri, typeof(VMManager)); HttpClient http = GetHttpClient(); HttpResponseMessage responseMessage = await http.DeleteAsync(uri); return responseMessage; }  And the following is the method which can used to delete both of deployment and service async public Task<string> DeleteVM(string vmName) { string responseString = string.Empty;   // as a convention here in this post, a unified name used for service, deployment and VM instance to make it easy to manage VMs HttpClient http = GetHttpClient(); HttpResponseMessage responseMessage = await DeleteDeployment(vmName);   if (responseMessage != null) {   string requestID = responseMessage.Headers.GetValues("x-ms-request-id").FirstOrDefault(); OperationResult result = await PollGetOperationStatus(requestID, 5, 120); if (result.Status == OperationStatus.Succeeded) { responseString = result.Message; HttpResponseMessage sResponseMessage = await DeleteService(vmName); if (sResponseMessage != null) { OperationResult sResult = await PollGetOperationStatus(requestID, 5, 120); responseString += sResult.Message; } } else { responseString = result.Message; } } return responseString; }  Note: This article is subject to be updated Hisham  References Advanced Windows Azure IaaS – Demo Code Windows Azure Service Management REST API Reference Introduction to the Azure Platform Representational state transfer Asynchronous Programming with Async and Await (C# and Visual Basic) HttpClient Class

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