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  • When creating a WCF Service with NetTcpBinding, use endpoint "localhost" or machine's host name?

    - by Elan
    I have a WCF service that uses the NetTcpBinding and is running within a Windows service. Remote clients connect to this service. So far, I have defined the endpoint to use "localhost". If the host machine has multiple network adapters, will it receive messages on all adapters? Would it be better to assign the machine's host name to the endpoint instead of "localhost"? What are the advantages/disadvantages?

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  • Is there any analog of TCPvcon which allows to close TCP connection on remote machine?

    - by Miollnyr
    Hi, I started to use SysInternals suite, and it is great. But I wonder, whether there is any analog of TCPvcon, which allows to logon to remote machine, like psexec does, and then get list of TCP connections from there (similar to pslist functionality), and then to close some of connections (similar to pskill functionality). I am speaking about windows console tools and I would like to avoid installing something on remote machine is this is possible.

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  • can I run C# built-in unit test in build machine?

    - by 5YrsLaterDBA
    can I run C# built-in unit test in build machine which doesn't have Visual Studio installed? We are thinking add unit test to our Visual Studio 2008 C# project. Our build machine doesn't have VS installed and we want to integrate the new unit test with our auto-build system. Is MSTest the executable to launch the Team Test unit test?

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  • how to open HTML page stored on client machine from aspx page.

    - by shania
    Hi, I m developing asp.net application in which I m opening HTML page that is stored on client machine on that page I have a link which will open aspx page on server, On that aspx page I have a button that will open another html page stored on client machine. Since I m new to web development Plz help me and suggest me some solutions for this ASAP. Thanks....

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  • Under what circumstances does it make sense to run a WCF client and server on the same machine?

    - by Rising Star
    In Learning WCF, by Michele Bustamante, there is a section that describes a binding called the NetNamedPipes binding. The books says that this binding can only be used for WCF services that will be called exclusively from the same machine. Under what circumstances would it make sense to use this? Ordinarily, I would write asynchronous code without using WCF... Why would Microsoft provide something for WCF that can only run on the same machine?

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  • NSXMLParser and Geonames

    - by Xcoder
    I'm trying to parse a call from Geonames with NSXMLParser in the iPhone SDK. I've used this before but for some reason I'm getting an empty dictionary back even though I get results back in a web browser. Can someone please point out what I may be doing wrong. Below is the code I'm using and the results that comes back pasting it in a browser. Thanks in advance #pragma mark - #pragma mark - Parcer Services -(void)beginLoadingFeed{ //[self startLoadingWithMessage:@"Loading Results...."]; NSInvocationOperation *operation = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(loadFeed) object:nil]; [operationQueue addOperation:operation]; [operation release]; } - (void)loadFeed{ NSString *path = [NSString stringWithFormat:@"http://ws.geonames.org/postalCodeSearch?placename=%@&long&maxRows=20",self.location]; [Logger log:@"Geonames Query: %@",path]; [self parseXMLFileAtURL:path]; [self performSelectorOnMainThread:@selector(didfinishedLoadingFeed) withObject:nil waitUntilDone:YES]; } -(void)didfinishedLoadingFeed{ } - (void)parserDidStartDocument:(NSXMLParser *)parser{ [Logger log:@"found file and started parsing"]; } //Called when the parser runs into an open tag (<tag>) - (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict { if ([elementName isEqualToString:@"code"]) { currentResult = [NSMutableDictionary dictionary]; } else { currentElement = [elementName copy]; } } //This is just to resolve random HTML entities - (NSData *)parser:(NSXMLParser *)parser resolveExternalEntityName:(NSString *)entityName systemID:(NSString *)systemID { return [entityName dataUsingEncoding:NSASCIIStringEncoding]; } - (void)parseXMLFileAtURL:(NSString *)URL{ self.results = [[[NSMutableArray alloc] init] autorelease]; NSURL *xmlURL = [NSURL URLWithString:URL]; NSXMLParser *parser = [[NSXMLParser alloc] initWithContentsOfURL:xmlURL]; [parser setDelegate:self]; [parser parse]; [parser autorelease]; } - (void)parser:(NSXMLParser *)parser parseErrorOccurred:(NSError *)parseError { NSString * errorString = [NSString stringWithFormat:@"Unable to connect to web site (Error code %i )", [parseError code]]; [Logger log:@"error parsing : %@", errorString]; [self stopLoadingView]; [self showMessage:@"Error loading content" withTitle:@"Error Loading"]; } /*** Called when the parser runs into a close tag (</tag>). If it is the Result tag that is closing, we should add the currentResult to the array, and then forget about it ***/ - (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName { if ([elementName isEqualToString:@"code"]) { [self.results addObject:currentResult]; currentResult = nil; } } - (void)parserDidEndDocument:(NSXMLParser *)parser { [Logger log:@"all done!"]; [Logger log:@"results array has %d items", [self.results count]]; [Logger log:@"Results:%@",results]; [theTableView reloadData]; [self stopLoadingView]; } Below is the result that comes back in a browser using the same call above when doing the search for the term "boston": <?xml version="1.0" encoding="UTF-8" standalone="no"?> <geonames> <totalResultsCount>2808</totalResultsCount> <code> <postalcode>02101</postalcode> <name>Boston</name> <countryCode>US</countryCode> <lat>42.370567</lat> <lng>-71.026964</lng> <adminCode1>MA</adminCode1> <adminName1>Massachusetts</adminName1> <adminCode2>025</adminCode2> <adminName2>Suffolk</adminName2> <adminCode3/> <adminName3/> </code> <code> <postalcode>02108</postalcode> <name>Boston</name> <countryCode>US</countryCode> <lat>42.357603</lat> <lng>-71.068432</lng> <adminCode1>MA</adminCode1> <adminName1>Massachusetts</adminName1> <adminCode2>025</adminCode2> <adminName2>Suffolk</adminName2> <adminCode3/> <adminName3/> </code> <code> <postalcode>02109</postalcode> <name>Boston</name> <countryCode>US</countryCode> <lat>42.360027</lat> <lng>-71.054495</lng> <adminCode1>MA</adminCode1> <adminName1>Massachusetts</adminName1> <adminCode2>025</adminCode2> <adminName2>Suffolk</adminName2> <adminCode3/> <adminName3/> </code> <code> <postalcode>02110</postalcode> <name>Boston</name> <countryCode>US</countryCode> <lat>42.357636</lat> <lng>-71.051417</lng> <adminCode1>MA</adminCode1> <adminName1>Massachusetts</adminName1> <adminCode2>025</adminCode2> <adminName2>Suffolk</adminName2> <adminCode3/> <adminName3/> </code> <code> <postalcode>02111</postalcode> <name>Boston</name> <countryCode>US</countryCode> <lat>42.350348</lat> <lng>-71.0629</lng> <adminCode1>MA</adminCode1> <adminName1>Massachusetts</adminName1> <adminCode2>025</adminCode2> <adminName2>Suffolk</adminName2> <adminCode3/> <adminName3/> </code> <code> <postalcode>02114</postalcode> <name>Boston</name> <countryCode>US</countryCode> <lat>42.361111</lat> <lng>-71.06823</lng> <adminCode1>MA</adminCode1> <adminName1>Massachusetts</adminName1> <adminCode2>025</adminCode2> <adminName2>Suffolk</adminName2> <adminCode3/> <adminName3/> </code> <code> <postalcode>02115</postalcode> <name>Boston</name> <countryCode>US</countryCode> <lat>42.342706</lat> <lng>-71.092215</lng> <adminCode1>MA</adminCode1> <adminName1>Massachusetts</adminName1> <adminCode2>025</adminCode2> <adminName2>Suffolk</adminName2> <adminCode3/> <adminName3/> </code> <code> <postalcode>02116</postalcode> <name>Boston</name> <countryCode>US</countryCode> <lat>42.349201</lat> <lng>-71.076798</lng> <adminCode1>MA</adminCode1> <adminName1>Massachusetts</adminName1> <adminCode2>025</adminCode2> <adminName2>Suffolk</adminName2> <adminCode3/> <adminName3/> </code> <code> <postalcode>02118</postalcode> <name>Boston</name> <countryCode>US</countryCode> <lat>42.336162</lat> <lng>-71.072854</lng> <adminCode1>MA</adminCode1> <adminName1>Massachusetts</adminName1> <adminCode2>025</adminCode2> <adminName2>Suffolk</adminName2> <adminCode3/> <adminName3/> </code> <code> <postalcode>02128</postalcode> <name>Boston</name> <countryCode>US</countryCode> <lat>42.364197</lat> <lng>-71.025694</lng> <adminCode1>MA</adminCode1> <adminName1>Massachusetts</adminName1> <adminCode2>025</adminCode2> <adminName2>Suffolk</adminName2> <adminCode3/> <adminName3/> </code> <code> <postalcode>02199</postalcode> <name>Boston</name> <countryCode>US</countryCode> <lat>42.347873</lat> <lng>-71.082543</lng> <adminCode1>MA</adminCode1> <adminName1>Massachusetts</adminName1> <adminCode2>025</adminCode2> <adminName2>Suffolk</adminName2> <adminCode3/> <adminName3/> </code> <code> <postalcode>02210</postalcode> <name>Boston</name> <countryCode>US</countryCode> <lat>42.348921</lat> <lng>-71.046511</lng> <adminCode1>MA</adminCode1> <adminName1>Massachusetts</adminName1> <adminCode2>025</adminCode2> <adminName2>Suffolk</adminName2> <adminCode3/> <adminName3/> </code> <code> <postalcode>02215</postalcode> <name>Boston</name> <countryCode>US</countryCode> <lat>42.347088</lat> <lng>-71.102689</lng> <adminCode1>MA</adminCode1> <adminName1>Massachusetts</adminName1> <adminCode2>025</adminCode2> <adminName2>Suffolk</adminName2> <adminCode3/> <adminName3/> </code> <code> <postalcode>22713</postalcode> <name>Boston</name> <countryCode>US</countryCode> <lat>38.538241</lat> <lng>-78.142285</lng> <adminCode1>VA</adminCode1> <adminName1>Virginia</adminName1> <adminCode2>047</adminCode2> <adminName2>Culpeper</adminName2> <adminCode3/> <adminName3/> </code> <code> <postalcode>24592</postalcode> <name>South Boston</name> <countryCode>US</countryCode> <lat>36.696335</lat> <lng>-78.918829</lng> <adminCode1>VA</adminCode1> <adminName1>Virginia</adminName1> <adminCode2>083</adminCode2> <adminName2>Halifax</adminName2> <adminCode3/> <adminName3/> </code> <code> <postalcode>02102</postalcode> <name>Boston</name> <countryCode>US</countryCode> <lat>42.338947</lat> <lng>-70.919635</lng> <adminCode1>MA</adminCode1> <adminName1>Massachusetts</adminName1> <adminCode2>025</adminCode2> <adminName2>Suffolk</adminName2> <adminCode3/> <adminName3/> </code> <code> <postalcode>02103</postalcode> <name>Boston</name> <countryCode>US</countryCode> <lat>42.338947</lat> <lng>-70.919635</lng> <adminCode1>MA</adminCode1> <adminName1>Massachusetts</adminName1> <adminCode2>025</adminCode2> <adminName2>Suffolk</adminName2> <adminCode3/> <adminName3/> </code> <code> <postalcode>02104</postalcode> <name>Boston</name> <countryCode>US</countryCode> <lat>42.338947</lat> <lng>-70.919635</lng> <adminCode1>MA</adminCode1> <adminName1>Massachusetts</adminName1> <adminCode2>025</adminCode2> <adminName2>Suffolk</adminName2> <adminCode3/> <adminName3/> </code> <code> <postalcode>02105</postalcode> <name>Boston</name> <countryCode>US</countryCode> <lat>42.338947</lat> <lng>-70.919635</lng> <adminCode1>MA</adminCode1> <adminName1>Massachusetts</adminName1> <adminCode2>025</adminCode2> <adminName2>Suffolk</adminName2> <adminCode3/> <adminName3/> </code> <code> <postalcode>02106</postalcode> <name>Boston</name> <countryCode>US</countryCode> <lat>42.354318</lat> <lng>-71.073449</lng> <adminCode1>MA</adminCode1> <adminName1>Massachusetts</adminName1> <adminCode2>025</adminCode2> <adminName2>Suffolk</adminName2> <adminCode3/> <adminName3/> </code> </geonames>

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  • By-Name-Parameters for Constructors

    - by hotzen
    Hello, coming from my other question is there a way to get by-name-parameters for constructors working? I need a way to provide a code-block which is executed on-demand/lazy/by-name inside an object and this code-block must be able to access the class-methods as if the code-block were part of the class. Following Testcase fails: package test class ByNameCons(code: => Unit) { def exec() = { println("pre-code") code println("post-code") } def meth() = println("method") def exec2(code2: => Unit) = { println("pre-code") code2 println("post-code") } } object ByNameCons { def main(args: Array[String]): Unit = { val tst = new ByNameCons { println("foo") meth() // knows meth() as code is part of ByNameCons } tst.exec() // ByName fails (executed right as constructor) println("--------") tst.exec2 { // ByName works println("foo") //meth() // does not know meth() as code is NOT part of ByNameCons } } } Output: foo method pre-code post-code -------- pre-code foo post-code

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  • Saving Types generated via Reflection.Emit as code file (.cs) instead of saving it in .dll files

    - by Manish Sinha
    Before start let me tell my experience: I am experienced with C#.NET, web services, XML part and few more. Reflection is something new to me, though I have read extensively on it and tried out some experimental code, but haven't made anything great using reflection I checked out many examples of how we can create Type at runtime and then which can be saved in an assembly (.dll) files. Of all the examples I have seen is about saving the created types in the .dll files instead of code file. Isn't there any way to create the code file out of reflection? I need to create code file since I want to distribute code instead of compiled assemblies. What I want to do is something like xsd.exe does, either spit out a .dll or the code file(in any language). Isn't there any way to create a code file, since most of the place I can find is AssemblyBuilder ab = System.AppDomain.CurrentDomain.DefineDynamicAssembly(an, AssemblyBuilderAccess.Save); and then lastly ab.Save("QuoteOfTheDay.dll");

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  • My error with upgrading 4.0 to 4.2- What NOT to do...

    - by Steve Tunstall
    Last week, I was helping a client upgrade from the 2011.1.4.0 code to the newest 2011.1.4.2 code. We downloaded the 4.2 update from MOS, upload and unpacked it on both controllers, and upgraded one of the controllers in the cluster with no issues at all. As this was a brand-new system with no networking or pools made on it yet, there were not any resources to fail back and forth between the controllers. Each controller had it's own, private, management interface (igb0 and igb1) and that's it. So we took controller 1 as the passive controller and upgraded it first. The first controller came back up with no issues and was now on the 4.2 code. Great. We then did a takeover on controller 1, making it the active head (although there were no resources for it to take), and then proceeded to upgrade controller 2. Upon upgrading the second controller, we ran the health check with no issues. We then ran the update and it ran and rebooted normally. However, something strange then happened. It took longer than normal to come back up, and when it did, we got the "cluster controllers on different code" error message that one gets when the two controllers of a cluster are running different code. But we just upgraded the second controller to 4.2, so they should have been the same, right??? Going into the Maintenance-->System screen of controller 2, we saw something very strange. The "current version" was still on 4.0, and the 4.2 code was there but was in the "previous" state with the rollback icon, as if it was the OLDER code and not the newer code. I have never seen this happen before. I would have thought it was a bad 4.2 code file, but it worked just fine with controller 1, so I don't think that was it. Other than the fact the code did not update, there was nothing else going on with this system. It had no yellow lights, no errors in the Problems section, and no errors in any of the logs. It was just out of the box a few hours ago, and didn't even have a storage pool yet. So.... We deleted the 4.2 code, uploaded it from scratch, ran the health check, and ran the upgrade again. once again, it seemed to go great, rebooted, and came back up to the same issue, where it came to 4.0 instead of 4.2. See the picture below.... HERE IS WHERE I MADE A BIG MISTAKE.... I SHOULD have instantly called support and opened a Sev 2 ticket. They could have done a shared shell and gotten the correct Fishwork engineer to look at the files and the code and determine what file was messed up and fixed it. The system was up and working just fine, it was just on an older code version, not really a huge problem at all. Instead, I went ahead and clicked the "Rollback" icon, thinking that the system would rollback to the 4.2 code.   Ouch... What happened was that the system said, "Fine, I will delete the 4.0 code and boot to your 4.2 code"... Which was stupid on my part because something was wrong with the 4.2 code file here and the 4.0 was just fine.  So now the system could not boot at all, and the 4.0 code was completely missing from the system, and even a high-level Fishworks engineer could not help us. I had messed it up good. We could only get to the ILOM, and I had to re-image the system from scratch using a hard-to-get-and-use FishStick USB drive. These are tightly controlled and difficult to get, almost always handcuffed to an engineer who will drive out to re-image a system. This took another day of my client's time.  So.... If you see a "previous version" of your system code which is actually a version higher than the current version... DO NOT ROLL IT BACK.... It did not upgrade for a very good reason. In my case, after the system was re-imaged to a code level just 3 back, we once again tried the same 4.2 code update and it worked perfectly the first time and is now great and stable.  Lesson learned.  By the way, our buddy Ryan Matthews wanted to point out the best practice and supported way of performing an upgrade of an active/active ZFSSA, where both controllers are doing some of the work. These steps would not have helpped me for the above issue, but it's important to follow the correct proceedure when doing an upgrade. 1) Upload software to both controllers and wait for it to unpack 2) On controller "A" navigate to configuration/cluster and click "takeover" 3) Wait for controller "B" to finish restarting, then login to it, navigate to maintenance/system, and roll forward to the new software. 4) Wait for controller "B" to apply the update and finish rebooting 5) Login to controller "B", navigate to configuration/cluster and click "takeover" 6) Wait for controller "A" to finish restarting, then login to it, navigate to maintenance/system, and roll forward to the new software. 7) Wait for controller "A" to apply the update and finish rebooting 8) Login to controller "B", navigate to configuration/cluster and click "failback"

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  • Beside SVN, how do you manage your development vs test vs production source code?

    - by medopal
    I'm working on a very large project with three phases of source code. Development source code: changes rapidly every second, and checked by our QA Test environment code: released to clients' QA department (released every 2-3 weeks) Production environment: after confirmed ok by client QA its released to prod. (every few months) The system (governmental web app) is very large to track changes,bugs and hot fixes, sometimes the Testers could ask for a change, some other times the Production could ask for a hot fix or small update. The problem is, when the Test or Production request changes, the development code is already changed a lot, and they always warn us they want only that small fix, do not upload anything new with it. The question, how should i manage the code for the 3 phases, and get back to Test or Production code any tie and fix that small one thing (reflecting the change to the current Development as well)? Note: making a branch each time is too much, and i don't want the developers to be lost between updating the mainstream, the branch and the Test code!

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  • Installation problem Ubuntu 12.04 Crashing hardware error

    - by user93640
    I am running on Ubuntu 8.04 for quite some time without many problems. About almost a year ago or so I have been trying to upgrade to 10.04 LTS, but without any success. Each time when trying to upgrade or even newly install the installation process crashed after about an hour or so (I forgot exactly how long). Now I wanted to try Ubuntu 12.04 (not even installing, but I only selected "Try Ubuntu without installing") and I got similar errors. I did not try to install it, because of earlier experience with 10.04 when after I also lost 8.04 and had to install from scratch again (after which it worked). I get the following screen (as I am not allowed to upload photos here the text): 26.767262] [Hardware Error]: CPU 0: Machine Check Exception: 0 Bank 5: b200001804000e0f 26.767279] [Hardware Error]: TSC 0 26.767287] [Hardware Error]: PROCESSOR 0:6f6 TIME 1349017924 SOCKET 0 APIC 0 microcode 44 26.767297] [Hardware Error]: Run the above through 'mcelog --ascii' 26.767307] [Hardware Error]: CPU 1: Machine Check Exception: 0 Bank 1: b200000000000175 26.767316] [Hardware Error]: TSC 0 26.767323] [Hardware Error]: PROCESSOR 0:6f6 TIME 1349017924 SOCKET 0 APIC 1 microcode 44 26.767331] [Hardware Error]: Run the above through 'mcelog --ascii' 26.767339] [Hardware Error]: CPU 1: Machine Check Exception: 0 Bank 5: b200003000000e0f 26.767348] [Hardware Error]: TSC 0 26.767354] [Hardware Error]: PROCESSOR 0:6f6 TIME 1349017924 SOCKET 0 APIC 1 microcode 44 26.767363] [Hardware Error]: Run the above through 'mcelog --ascii' 26.767371] [Hardware Error]: CPU 1: Machine Check Exception: 4 Bank 1: b200000000000175 26.767379] [Hardware Error]: TSC 1bf231e65f 26.767386] [Hardware Error]: PROCESSOR 0:6f6 TIME 1349017951 SOCKET 0 APIC 1 microcode 44 26.767395] [Hardware Error]: Run the above through 'mcelog --ascii' 26.767403] [Hardware Error]: CPU 1: Machine Check Exception: 4 Bank 5: b200003008000e0f 26.767413] [Hardware Error]: TSC 1bf231e65f 26.767421] [Hardware Error]: PROCESSOR 0:6f6 TIME 1349017951 SOCKET 0 APIC 1 microcode 44 26.767429] [Hardware Error]: Run the above through 'mcelog --ascii' 26.767437] [Hardware Error]: CPU 0: Machine Check Exception: 5 Bank 5: b200001806000e0f 26.767447] [Hardware Error]: RIP |INEXACT| 60:<00000000c1018b5c> {mwait_idle+0x7c/0x1d0} 26.767464] [Hardware Error]: TSC 1bf231e674 26.767471] [Hardware Error]: PROCESSOR 0:6f6 TIME 1349017951 SOCKET 0 APIC 0 microcode 44 26.767480] [Hardware Error]: Run the above through 'mcelog --ascii' 26.767487] [Hardware Error]: Machine check: Processor context corrupt 26.767495] Kernel panic - not syncing: Fatal Machine check 26.767505] Pid: 579, comm: debconf-communi Tainted: G M 3.2.0.29-generic-pae #46-Ubuntu 26.767515] Call Trace: 26.767525] [<c158f812>] ? printk+0x2d/0x2f 26.767534] [<c158f6e0>] panic+0x5c/0x161 26.767542] [<c10247ef>] mce_panic.part.14+0x13f/0x170 26.767551] [<c1024872>] mce_panic+0x52/0x90 26.767558] [<c1024a18>] mce_reign+0x168/0x170 26.767565] [<c1024bb5>] mce_end+0x105/0x110 26.767572] [<c10252db>] do_machine_check+0x32b/0x4f0 26.767581] [<c1024fb0>] ? mce_log+0x120/0x120 26.767590] [<c15a5e47>] error_code+0x67/0x6c 26.767602] panic occurred, switching back to text console 26.768498] Rebooting in 30 seconds.. For information, I have also tried earlier Arch Linux. I can install it, but when I try to install a window manager (LXDE) again I got similar errors. Fedora also crashes when installing and also Mandriva did not work for me. Therefore I think something deep in the machine might be wrong. But as stated above I can (clean) install 8.04 and also 9.10 can be installed without problems. Also updates for 8.04 can be installed. My machine is dual boot with XP next to it on a different partition. My HW: Memory : 2.0 GiB; Processor 0: Intel(R) Core(TM)2 CPU 6320 @ 1.86GHz; Processor 1: Intel(R) Core(TM)2 CPU 6320 @ 1.86GHz; How can I install Ubuntu 12.04? Last option would be to completely format my machine and install everything from scratch, but even I am not sure if that would solve it in the end. Can anybody help me out?

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  • How do you install .net4 on a Server 2008 r2 machine through psremoting in powershell?

    - by Jake
    I need to write a script that installs .net 4 remotely using powershell to a group of Server 2008 R2 machines. I based my script off of http://social.technet.microsoft.com/Forums/en-US/winserverpowershell/thread/3045eb24-7739-4695-ae94-5aa7052119fd/. enter-pssession -computername localhost $arglist = "/q /norestart /log C:\Users\tempuser\Desktop\dotnetfx4" $filepath = "C:\Users\tempuser\Desktop\dotNetFx40_Full_setup.exe" Start-Process -FilePath $filepath -ArgumentList $arglist -Wait -PassThru After running the command I would get the following log errors (running the same lines locally would install .net without error): Action: Downloading Item Failed to CreateJob : hr= 0x80200014 Action: Performing actions on all Items Action: Performing Action on Exe at C:\Users\tempuser\Desktop\dotnetfx4\SetupUtility.exe Exe (C:\Users\tempuser\Desktop\dotnetfx4\SetupUtility.exe) succeeded. Exe Log File: dd_SetupUtility.txt Action complete Action: ServiceControl - Stop clr_optimization_v2.0.50727_32 ServiceControl operation succeeded! Action complete Action: ServiceControl - Stop clr_optimization_v2.0.50727_64 ServiceControl operation succeeded! Action complete Action: Performing Action on Exe at C:\Users\tempuser\AppData\Local\Temp\Microsoft .NET Framework 4 Setup_4.0.30319\Windows6.1-KB958488-v6001-x64.msu Exe (C:\Users\tempuser\AppData\Local\Temp\Microsoft .NET Framework 4 Setup_4.0.30319\Windows6.1-KB958488-v6001-x64.msu) failed with 0x5 - Access is denied. . PerformOperation on exe returned exit code 5 (translates to HRESULT = 0x5) Action complete OnFailureBehavior for this item is to Rollback. Action: Performing actions on all Items Action complete Action complete Action: Downloading http://go.microsoft.com/fwlink/?LinkId=164184&clcid=0x409 using WinHttp WinHttpDetectAutoProxyConfigUrl failed with error: 12180 Unable to retrieve Proxy information although WinHttpGetIEProxyConfigForCurrentUser called succeeded Action complete C:\Users\tempuser\AppData\Local\Temp\Microsoft .NET Framework 4 Setup_4.0.30319\TMPF279.tmp.exe: Verifying signature for netfx_Core.mzz C:\Users\tempuser\AppData\Local\Temp\Microsoft .NET Framework 4 Setup_4.0.30319\TMPF279.tmp.exe Signature verified successfully for netfx_Core.mzz Action complete Decompression completed with code: 16389 Decompression of payload failed: C:\Users\tempuser\AppData\Local\Temp\Microsoft .NET Framework 4 Setup_4.0.30319\netfx_Core.mzz Action complete Final Result: Installation failed with error code: (0x80074005) (Elapsed time: 0 00:00:28). Is there some security setting or perhaps something else I've missed?

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  • Toorcon 15 (2013)

    - by danx
    The Toorcon gang (senior staff): h1kari (founder), nfiltr8, and Geo Introduction to Toorcon 15 (2013) A Tale of One Software Bypass of MS Windows 8 Secure Boot Breaching SSL, One Byte at a Time Running at 99%: Surviving an Application DoS Security Response in the Age of Mass Customized Attacks x86 Rewriting: Defeating RoP and other Shinanighans Clowntown Express: interesting bugs and running a bug bounty program Active Fingerprinting of Encrypted VPNs Making Attacks Go Backwards Mask Your Checksums—The Gorry Details Adventures with weird machines thirty years after "Reflections on Trusting Trust" Introduction to Toorcon 15 (2013) Toorcon 15 is the 15th annual security conference held in San Diego. I've attended about a third of them and blogged about previous conferences I attended here starting in 2003. As always, I've only summarized the talks I attended and interested me enough to write about them. Be aware that I may have misrepresented the speaker's remarks and that they are not my remarks or opinion, or those of my employer, so don't quote me or them. Those seeking further details may contact the speakers directly or use The Google. For some talks, I have a URL for further information. A Tale of One Software Bypass of MS Windows 8 Secure Boot Andrew Furtak and Oleksandr Bazhaniuk Yuri Bulygin, Oleksandr ("Alex") Bazhaniuk, and (not present) Andrew Furtak Yuri and Alex talked about UEFI and Bootkits and bypassing MS Windows 8 Secure Boot, with vendor recommendations. They previously gave this talk at the BlackHat 2013 conference. MS Windows 8 Secure Boot Overview UEFI (Unified Extensible Firmware Interface) is interface between hardware and OS. UEFI is processor and architecture independent. Malware can replace bootloader (bootx64.efi, bootmgfw.efi). Once replaced can modify kernel. Trivial to replace bootloader. Today many legacy bootkits—UEFI replaces them most of them. MS Windows 8 Secure Boot verifies everything you load, either through signatures or hashes. UEFI firmware relies on secure update (with signed update). You would think Secure Boot would rely on ROM (such as used for phones0, but you can't do that for PCs—PCs use writable memory with signatures DXE core verifies the UEFI boat loader(s) OS Loader (winload.efi, winresume.efi) verifies the OS kernel A chain of trust is established with a root key (Platform Key, PK), which is a cert belonging to the platform vendor. Key Exchange Keys (KEKs) verify an "authorized" database (db), and "forbidden" database (dbx). X.509 certs with SHA-1/SHA-256 hashes. Keys are stored in non-volatile (NV) flash-based NVRAM. Boot Services (BS) allow adding/deleting keys (can't be accessed once OS starts—which uses Run-Time (RT)). Root cert uses RSA-2048 public keys and PKCS#7 format signatures. SecureBoot — enable disable image signature checks SetupMode — update keys, self-signed keys, and secure boot variables CustomMode — allows updating keys Secure Boot policy settings are: always execute, never execute, allow execute on security violation, defer execute on security violation, deny execute on security violation, query user on security violation Attacking MS Windows 8 Secure Boot Secure Boot does NOT protect from physical access. Can disable from console. Each BIOS vendor implements Secure Boot differently. There are several platform and BIOS vendors. It becomes a "zoo" of implementations—which can be taken advantage of. Secure Boot is secure only when all vendors implement it correctly. Allow only UEFI firmware signed updates protect UEFI firmware from direct modification in flash memory protect FW update components program SPI controller securely protect secure boot policy settings in nvram protect runtime api disable compatibility support module which allows unsigned legacy Can corrupt the Platform Key (PK) EFI root certificate variable in SPI flash. If PK is not found, FW enters setup mode wich secure boot turned off. Can also exploit TPM in a similar manner. One is not supposed to be able to directly modify the PK in SPI flash from the OS though. But they found a bug that they can exploit from User Mode (undisclosed) and demoed the exploit. It loaded and ran their own bootkit. The exploit requires a reboot. Multiple vendors are vulnerable. They will disclose this exploit to vendors in the future. Recommendations: allow only signed updates protect UEFI fw in ROM protect EFI variable store in ROM Breaching SSL, One Byte at a Time Yoel Gluck and Angelo Prado Angelo Prado and Yoel Gluck, Salesforce.com CRIME is software that performs a "compression oracle attack." This is possible because the SSL protocol doesn't hide length, and because SSL compresses the header. CRIME requests with every possible character and measures the ciphertext length. Look for the plaintext which compresses the most and looks for the cookie one byte-at-a-time. SSL Compression uses LZ77 to reduce redundancy. Huffman coding replaces common byte sequences with shorter codes. US CERT thinks the SSL compression problem is fixed, but it isn't. They convinced CERT that it wasn't fixed and they issued a CVE. BREACH, breachattrack.com BREACH exploits the SSL response body (Accept-Encoding response, Content-Encoding). It takes advantage of the fact that the response is not compressed. BREACH uses gzip and needs fairly "stable" pages that are static for ~30 seconds. It needs attacker-supplied content (say from a web form or added to a URL parameter). BREACH listens to a session's requests and responses, then inserts extra requests and responses. Eventually, BREACH guesses a session's secret key. Can use compression to guess contents one byte at-a-time. For example, "Supersecret SupersecreX" (a wrong guess) compresses 10 bytes, and "Supersecret Supersecret" (a correct guess) compresses 11 bytes, so it can find each character by guessing every character. To start the guess, BREACH needs at least three known initial characters in the response sequence. Compression length then "leaks" information. Some roadblocks include no winners (all guesses wrong) or too many winners (multiple possibilities that compress the same). The solutions include: lookahead (guess 2 or 3 characters at-a-time instead of 1 character). Expensive rollback to last known conflict check compression ratio can brute-force first 3 "bootstrap" characters, if needed (expensive) block ciphers hide exact plain text length. Solution is to align response in advance to block size Mitigations length: use variable padding secrets: dynamic CSRF tokens per request secret: change over time separate secret to input-less servlets Future work eiter understand DEFLATE/GZIP HTTPS extensions Running at 99%: Surviving an Application DoS Ryan Huber Ryan Huber, Risk I/O Ryan first discussed various ways to do a denial of service (DoS) attack against web services. One usual method is to find a slow web page and do several wgets. Or download large files. Apache is not well suited at handling a large number of connections, but one can put something in front of it Can use Apache alternatives, such as nginx How to identify malicious hosts short, sudden web requests user-agent is obvious (curl, python) same url requested repeatedly no web page referer (not normal) hidden links. hide a link and see if a bot gets it restricted access if not your geo IP (unless the website is global) missing common headers in request regular timing first seen IP at beginning of attack count requests per hosts (usually a very large number) Use of captcha can mitigate attacks, but you'll lose a lot of genuine users. Bouncer, goo.gl/c2vyEc and www.github.com/rawdigits/Bouncer Bouncer is software written by Ryan in netflow. Bouncer has a small, unobtrusive footprint and detects DoS attempts. It closes blacklisted sockets immediately (not nice about it, no proper close connection). Aggregator collects requests and controls your web proxies. Need NTP on the front end web servers for clean data for use by bouncer. Bouncer is also useful for a popularity storm ("Slashdotting") and scraper storms. Future features: gzip collection data, documentation, consumer library, multitask, logging destroyed connections. Takeaways: DoS mitigation is easier with a complete picture Bouncer designed to make it easier to detect and defend DoS—not a complete cure Security Response in the Age of Mass Customized Attacks Peleus Uhley and Karthik Raman Peleus Uhley and Karthik Raman, Adobe ASSET, blogs.adobe.com/asset/ Peleus and Karthik talked about response to mass-customized exploits. Attackers behave much like a business. "Mass customization" refers to concept discussed in the book Future Perfect by Stan Davis of Harvard Business School. Mass customization is differentiating a product for an individual customer, but at a mass production price. For example, the same individual with a debit card receives basically the same customized ATM experience around the world. Or designing your own PC from commodity parts. Exploit kits are another example of mass customization. The kits support multiple browsers and plugins, allows new modules. Exploit kits are cheap and customizable. Organized gangs use exploit kits. A group at Berkeley looked at 77,000 malicious websites (Grier et al., "Manufacturing Compromise: The Emergence of Exploit-as-a-Service", 2012). They found 10,000 distinct binaries among them, but derived from only a dozen or so exploit kits. Characteristics of Mass Malware: potent, resilient, relatively low cost Technical characteristics: multiple OS, multipe payloads, multiple scenarios, multiple languages, obfuscation Response time for 0-day exploits has gone down from ~40 days 5 years ago to about ~10 days now. So the drive with malware is towards mass customized exploits, to avoid detection There's plenty of evicence that exploit development has Project Manager bureaucracy. They infer from the malware edicts to: support all versions of reader support all versions of windows support all versions of flash support all browsers write large complex, difficult to main code (8750 lines of JavaScript for example Exploits have "loose coupling" of multipe versions of software (adobe), OS, and browser. This allows specific attacks against specific versions of multiple pieces of software. Also allows exploits of more obscure software/OS/browsers and obscure versions. Gave examples of exploits that exploited 2, 3, 6, or 14 separate bugs. However, these complete exploits are more likely to be buggy or fragile in themselves and easier to defeat. Future research includes normalizing malware and Javascript. Conclusion: The coming trend is that mass-malware with mass zero-day attacks will result in mass customization of attacks. x86 Rewriting: Defeating RoP and other Shinanighans Richard Wartell Richard Wartell The attack vector we are addressing here is: First some malware causes a buffer overflow. The malware has no program access, but input access and buffer overflow code onto stack Later the stack became non-executable. The workaround malware used was to write a bogus return address to the stack jumping to malware Later came ASLR (Address Space Layout Randomization) to randomize memory layout and make addresses non-deterministic. The workaround malware used was to jump t existing code segments in the program that can be used in bad ways "RoP" is Return-oriented Programming attacks. RoP attacks use your own code and write return address on stack to (existing) expoitable code found in program ("gadgets"). Pinkie Pie was paid $60K last year for a RoP attack. One solution is using anti-RoP compilers that compile source code with NO return instructions. ASLR does not randomize address space, just "gadgets". IPR/ILR ("Instruction Location Randomization") randomizes each instruction with a virtual machine. Richard's goal was to randomize a binary with no source code access. He created "STIR" (Self-Transofrming Instruction Relocation). STIR disassembles binary and operates on "basic blocks" of code. The STIR disassembler is conservative in what to disassemble. Each basic block is moved to a random location in memory. Next, STIR writes new code sections with copies of "basic blocks" of code in randomized locations. The old code is copied and rewritten with jumps to new code. the original code sections in the file is marked non-executible. STIR has better entropy than ASLR in location of code. Makes brute force attacks much harder. STIR runs on MS Windows (PEM) and Linux (ELF). It eliminated 99.96% or more "gadgets" (i.e., moved the address). Overhead usually 5-10% on MS Windows, about 1.5-4% on Linux (but some code actually runs faster!). The unique thing about STIR is it requires no source access and the modified binary fully works! Current work is to rewrite code to enforce security policies. For example, don't create a *.{exe,msi,bat} file. Or don't connect to the network after reading from the disk. Clowntown Express: interesting bugs and running a bug bounty program Collin Greene Collin Greene, Facebook Collin talked about Facebook's bug bounty program. Background at FB: FB has good security frameworks, such as security teams, external audits, and cc'ing on diffs. But there's lots of "deep, dark, forgotten" parts of legacy FB code. Collin gave several examples of bountied bugs. Some bounty submissions were on software purchased from a third-party (but bounty claimers don't know and don't care). We use security questions, as does everyone else, but they are basically insecure (often easily discoverable). Collin didn't expect many bugs from the bounty program, but they ended getting 20+ good bugs in first 24 hours and good submissions continue to come in. Bug bounties bring people in with different perspectives, and are paid only for success. Bug bounty is a better use of a fixed amount of time and money versus just code review or static code analysis. The Bounty program started July 2011 and paid out $1.5 million to date. 14% of the submissions have been high priority problems that needed to be fixed immediately. The best bugs come from a small % of submitters (as with everything else)—the top paid submitters are paid 6 figures a year. Spammers like to backstab competitors. The youngest sumitter was 13. Some submitters have been hired. Bug bounties also allows to see bugs that were missed by tools or reviews, allowing improvement in the process. Bug bounties might not work for traditional software companies where the product has release cycle or is not on Internet. Active Fingerprinting of Encrypted VPNs Anna Shubina Anna Shubina, Dartmouth Institute for Security, Technology, and Society (I missed the start of her talk because another track went overtime. But I have the DVD of the talk, so I'll expand later) IPsec leaves fingerprints. Using netcat, one can easily visually distinguish various crypto chaining modes just from packet timing on a chart (example, DES-CBC versus AES-CBC) One can tell a lot about VPNs just from ping roundtrips (such as what router is used) Delayed packets are not informative about a network, especially if far away from the network More needed to explore about how TCP works in real life with respect to timing Making Attacks Go Backwards Fuzzynop FuzzyNop, Mandiant This talk is not about threat attribution (finding who), product solutions, politics, or sales pitches. But who are making these malware threats? It's not a single person or group—they have diverse skill levels. There's a lot of fat-fingered fumblers out there. Always look for low-hanging fruit first: "hiding" malware in the temp, recycle, or root directories creation of unnamed scheduled tasks obvious names of files and syscalls ("ClearEventLog") uncleared event logs. Clearing event log in itself, and time of clearing, is a red flag and good first clue to look for on a suspect system Reverse engineering is hard. Disassembler use takes practice and skill. A popular tool is IDA Pro, but it takes multiple interactive iterations to get a clean disassembly. Key loggers are used a lot in targeted attacks. They are typically custom code or built in a backdoor. A big tip-off is that non-printable characters need to be printed out (such as "[Ctrl]" "[RightShift]") or time stamp printf strings. Look for these in files. Presence is not proof they are used. Absence is not proof they are not used. Java exploits. Can parse jar file with idxparser.py and decomile Java file. Java typially used to target tech companies. Backdoors are the main persistence mechanism (provided externally) for malware. Also malware typically needs command and control. Application of Artificial Intelligence in Ad-Hoc Static Code Analysis John Ashaman John Ashaman, Security Innovation Initially John tried to analyze open source files with open source static analysis tools, but these showed thousands of false positives. Also tried using grep, but tis fails to find anything even mildly complex. So next John decided to write his own tool. His approach was to first generate a call graph then analyze the graph. However, the problem is that making a call graph is really hard. For example, one problem is "evil" coding techniques, such as passing function pointer. First the tool generated an Abstract Syntax Tree (AST) with the nodes created from method declarations and edges created from method use. Then the tool generated a control flow graph with the goal to find a path through the AST (a maze) from source to sink. The algorithm is to look at adjacent nodes to see if any are "scary" (a vulnerability), using heuristics for search order. The tool, called "Scat" (Static Code Analysis Tool), currently looks for C# vulnerabilities and some simple PHP. Later, he plans to add more PHP, then JSP and Java. For more information see his posts in Security Innovation blog and NRefactory on GitHub. Mask Your Checksums—The Gorry Details Eric (XlogicX) Davisson Eric (XlogicX) Davisson Sometimes in emailing or posting TCP/IP packets to analyze problems, you may want to mask the IP address. But to do this correctly, you need to mask the checksum too, or you'll leak information about the IP. Problem reports found in stackoverflow.com, sans.org, and pastebin.org are usually not masked, but a few companies do care. If only the IP is masked, the IP may be guessed from checksum (that is, it leaks data). Other parts of packet may leak more data about the IP. TCP and IP checksums both refer to the same data, so can get more bits of information out of using both checksums than just using one checksum. Also, one can usually determine the OS from the TTL field and ports in a packet header. If we get hundreds of possible results (16x each masked nibble that is unknown), one can do other things to narrow the results, such as look at packet contents for domain or geo information. With hundreds of results, can import as CSV format into a spreadsheet. Can corelate with geo data and see where each possibility is located. Eric then demoed a real email report with a masked IP packet attached. Was able to find the exact IP address, given the geo and university of the sender. Point is if you're going to mask a packet, do it right. Eric wouldn't usually bother, but do it correctly if at all, to not create a false impression of security. Adventures with weird machines thirty years after "Reflections on Trusting Trust" Sergey Bratus Sergey Bratus, Dartmouth College (and Julian Bangert and Rebecca Shapiro, not present) "Reflections on Trusting Trust" refers to Ken Thompson's classic 1984 paper. "You can't trust code that you did not totally create yourself." There's invisible links in the chain-of-trust, such as "well-installed microcode bugs" or in the compiler, and other planted bugs. Thompson showed how a compiler can introduce and propagate bugs in unmodified source. But suppose if there's no bugs and you trust the author, can you trust the code? Hell No! There's too many factors—it's Babylonian in nature. Why not? Well, Input is not well-defined/recognized (code's assumptions about "checked" input will be violated (bug/vunerabiliy). For example, HTML is recursive, but Regex checking is not recursive. Input well-formed but so complex there's no telling what it does For example, ELF file parsing is complex and has multiple ways of parsing. Input is seen differently by different pieces of program or toolchain Any Input is a program input executes on input handlers (drives state changes & transitions) only a well-defined execution model can be trusted (regex/DFA, PDA, CFG) Input handler either is a "recognizer" for the inputs as a well-defined language (see langsec.org) or it's a "virtual machine" for inputs to drive into pwn-age ELF ABI (UNIX/Linux executible file format) case study. Problems can arise from these steps (without planting bugs): compiler linker loader ld.so/rtld relocator DWARF (debugger info) exceptions The problem is you can't really automatically analyze code (it's the "halting problem" and undecidable). Only solution is to freeze code and sign it. But you can't freeze everything! Can't freeze ASLR or loading—must have tables and metadata. Any sufficiently complex input data is the same as VM byte code Example, ELF relocation entries + dynamic symbols == a Turing Complete Machine (TM). @bxsays created a Turing machine in Linux from relocation data (not code) in an ELF file. For more information, see Rebecca "bx" Shapiro's presentation from last year's Toorcon, "Programming Weird Machines with ELF Metadata" @bxsays did same thing with Mach-O bytecode Or a DWARF exception handling data .eh_frame + glibc == Turning Machine X86 MMU (IDT, GDT, TSS): used address translation to create a Turning Machine. Page handler reads and writes (on page fault) memory. Uses a page table, which can be used as Turning Machine byte code. Example on Github using this TM that will fly a glider across the screen Next Sergey talked about "Parser Differentials". That having one input format, but two parsers, will create confusion and opportunity for exploitation. For example, CSRs are parsed during creation by cert requestor and again by another parser at the CA. Another example is ELF—several parsers in OS tool chain, which are all different. Can have two different Program Headers (PHDRs) because ld.so parses multiple PHDRs. The second PHDR can completely transform the executable. This is described in paper in the first issue of International Journal of PoC. Conclusions trusting computers not only about bugs! Bugs are part of a problem, but no by far all of it complex data formats means bugs no "chain of trust" in Babylon! (that is, with parser differentials) we need to squeeze complexity out of data until data stops being "code equivalent" Further information See and langsec.org. USENIX WOOT 2013 (Workshop on Offensive Technologies) for "weird machines" papers and videos.

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  • Differences in cg shader code for OpenGL vs. for DirectX?

    - by Cray
    I have been trying to use an existing library that automatically generates shaders (Hydrax plugin for Ogre3D). These shaders are used to render water and somewhat involved, but are not extremely complicated. However there seems to be some differences in how the cg shaders are handled by OpenGL and DirectX, more specifically, I am pretty sure that the author of the library only has debugged all the shaders for DirectX, and they work flawlessly there, but not so in OpenGL. There are no compiler errors, but the result just doesn't look the same. (And I have to run the library in OpenGL.) Isn't cg supposed to be a language that can freely use the exact same code for both platforms? Are there any specific known caveats one should know about when using the same code for them? Are there any fast ways to find what parts of the code work differently? (I am pretty sure that the shaders are the problem. Otherwise Ogre3D has great support for both problems, and everything is abstracted away nicely. Other shaders work in OpenGL, etc...)

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  • API Message Localization

    - by Jesse Taber
    In my post, “Keep Localizable Strings Close To Your Users” I talked about the internationalization and localization difficulties that can arise when you sprinkle static localizable strings throughout the different logical layers of an application. The main point of that post is that you should have your localizable strings reside as close to the user-facing modules of your application as possible. For example, if you’re developing an ASP .NET web forms application all of the localizable strings should be kept in .resx files that are associated with the .aspx views of the application. In this post I want to talk about how this same concept can be applied when designing and developing APIs. An API Facilitates Machine-to-Machine Interaction You can typically think about a web, desktop, or mobile application as a collection “views” or “screens” through which users interact with the underlying logic and data. The application can be designed based on the assumption that there will be a human being on the other end of the screen working the controls. You are designing a machine-to-person interaction and the application should be built in a way that facilitates the user’s clear understanding of what is going on. Dates should be be formatted in a way that the user will be familiar with, messages should be presented in the user’s preferred language, etc. When building an API, however, there are no screens and you can’t make assumptions about who or what is on the other end of each call. An API is, by definition, a machine-to-machine interaction. A machine-to-machine interaction should be built in a way that facilitates a clear and unambiguous understanding of what is going on. Dates and numbers should be formatted in predictable and standard ways (e.g. ISO 8601 dates) and messages should be presented in machine-parseable formats. For example, consider an API for a time tracking system that exposes a resource for creating a new time entry. The JSON for creating a new time entry for a user might look like: 1: { 2: "userId": 4532, 3: "startDateUtc": "2012-10-22T14:01:54.98432Z", 4: "endDateUtc": "2012-10-22T11:34:45.29321Z" 5: }   Note how the parameters for start and end date are both expressed as ISO 8601 compliant dates in UTC. Using a date format like this in our API leaves little room for ambiguity. It’s also important to note that using ISO 8601 dates is a much, much saner thing than the \/Date(<milliseconds since epoch>)\/ nonsense that is sometimes used in JSON serialization. Probably the most important thing to note about the JSON snippet above is the fact that the end date comes before the start date! The API should recognize that and disallow the time entry from being created, returning an error to the caller. You might inclined to send a response that looks something like this: 1: { 2: "errors": [ {"message" : "The end date must come after the start date"}] 3: }   While this may seem like an appropriate thing to do there are a few problems with this approach: What if there is a user somewhere on the other end of the API call that doesn’t speak English?  What if the message provided here won’t fit properly within the UI of the application that made the API call? What if the verbiage of the message isn’t consistent with the rest of the application that made the API call? What if there is no user directly on the other end of the API call (e.g. this is a batch job uploading time entries once per night unattended)? The API knows nothing about the context from which the call was made. There are steps you could take to given the API some context (e.g.allow the caller to send along a language code indicating the language that the end user speaks), but that will only get you so far. As the designer of the API you could make some assumptions about how the API will be called, but if we start making assumptions we could very easily make the wrong assumptions. In this situation it’s best to make no assumptions and simply design the API in such a way that the caller has the responsibility to convey error messages in a manner that is appropriate for the context in which the error was raised. You would work around some of these problems by allowing callers to add metadata to each request describing the context from which the call is being made (e.g. accepting a ‘locale’ parameter denoting the desired language), but that will add needless clutter and complexity. It’s better to keep the API simple and push those context-specific concerns down to the caller whenever possible. For our very simple time entry example, this can be done by simply changing our error message response to look like this: 1: { 2: "errors": [ {"code": 100}] 3: }   By changing our error error from exposing a string to a numeric code that is easily parseable by another application, we’ve placed all of the responsibility for conveying the actual meaning of the error message on the caller. It’s best to have the caller be responsible for conveying this meaning because the caller understands the context much better than the API does. Now the caller can see error code 100, know that it means that the end date submitted falls before the start date and take appropriate action. Now all of the problems listed out above are non-issues because the caller can simply translate the error code of ‘100’ into the proper action and message for the current context. The numeric code representation of the error is a much better way to facilitate the machine-to-machine interaction that the API is meant to facilitate. An API Does Have Human Users While APIs should be built for machine-to-machine interaction, people still need to wire these interactions together. As a programmer building a client application that will consume the time entry API I would find it frustrating to have to go dig through the API documentation every time I encounter a new error code (assuming the documentation exists and is accurate). The numeric error code approach hurts the discoverability of the API and makes it painful to integrate with. We can help ease this pain by merging our two approaches: 1: { 2: "errors": [ {"code": 100, "message" : "The end date must come after the start date"}] 3: }   Now we have an easily parseable numeric error code for the machine-to-machine interaction that the API is meant to facilitate and a human-readable message for programmers working with the API. The human-readable message here is not intended to be viewed by end-users of the API and as such is not really a “localizable string” in my opinion. We could opt to expose a locale parameter for all API methods and store translations for all error messages, but that’s a lot of extra effort and overhead that doesn’t add a lot real value to the API. I might be a bit of an “ugly American”, but I think it’s probably fine to have the API return English messages when the target for those messages is a programmer. When resources are limited (which they always are), I’d argue that you’re better off hard-coding these messages in English and putting more effort into building more useful features, improving security, tweaking performance, etc.

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