I was wondering if I can implement bi-directional communication channel between 2 kext modules using sockets under the domain PF_SYSTEM. this method mostly used to communicate between driver and user-space agent..
In my particular case I've got one module based on IOKit and the other which is simple kernel module with start and stop callback functions and I'd like to pass some small messages between them..
Do you think this approach is suitable for my needs or there's other preferable way (shared memory ? mach ports ? )
EDIT, after digging a little deeper, maybe there's an option to export an API from one driver to the other by modifying the client driver plist file as follows.. is it possible ?
<key>OSBundleLibraries</key>
<dict>
<key>com.driver.server_driver</key>
<string>1</string>
This however, doesn't work because when i try to manually load the client driver after the server driver already loaded (visible from kextstat), I get the No kexts found for these libraries error.
Using messaging techniques normally used for IPC for communicationg between kernel extensions is unusual, as it's a lot more complex than taking advantage of the fact that they're running in the same address space anyway. I covered some of the details of this latter approach in my answer to your other question which you've obviously already seen, but I'm linking to for the benefit of others in a similar situation.
To answer your question: I suspect both ends of a system socket being in the kernel is probably not very well tested, and you could run into bugs in the kernel. The in-kernel public socket KPI is also quite fiddly: getting the buffering right is tricky, so I'd only use sockets if I absolutely had to, and it clearly isn't here.
My gut instinct is that Mach messaging would work more reliably and require less code, but again I think it would be quite unusual to use it in this way.
It's hard to give useful advice on exactly what you should do, as we don't know the reasons for the separation into 2 kexts, what their relationship is, what kind of communication is required, etc. There are many possible ways on how to exchange information, but whether they are a good idea will depend on the details of the project. (This sort of question isn't really suitable to Stack Overflow's format - this is the sort of problem for which a company will bring in an expert to consult. For a private project, you might have more luck on the Software Engineering Stack Exchange Site, where this sort of question is on-topic, although I'm not sure you'll get a good/useful answer. For a private project it's probably best you keep it simple and maybe combine the 2 kexts into one?)
How do I implement activesync protocol in iphone app?
Any advice, any docs and tutorials are well come.
I have read the Exchange ActiveSync and iOS 4 Devices from apple.
Is there any real docs for this?
Despite having asked a question in the comment, you might be looking for the Microsoft documentation of the Exchange Server Protocols.
If you're thinking of implementing your own client though, I would strongly advise you to pause and consider whether it's really worth it. As someone who's worked on a server-side implementation of these protocols, I can tell you they can get pretty complicated - and the documentation doesn't always give you enough information. (In some areas it's flat out wrong, too.)
It is hard, but not impossible to write an app which communicates via exchange active sync. The link to the Exchange Server Protocols in Jons answer contains a document named MS-ASWBXML. You have to write an encoder for wbxml on your own and the document describes clearly the needs. Additionaly I recommend strongly this document: http://www.w3.org/TR/wbxml/
If the low level is working, you have to implement the EAS-protocol on top ob wbxml, which is not trivial, because of bugs in the documentation, different behaviour of different protocol versions. It will be a lot of trial an error to examine, why the exchange server does not understand your requests ;-)
Using Apple's built in support just means using Apple's APIs for writing to the Address Book and Calendar Store on the phone. Your app isn't supposed to know anything about the way that data is synchronised: it just happens in the background.
If you want direct control over the synchronisation process, then Apple's APIs cannot help you. Jon Skeet's answer contains a link to Microsoft's protocol documentation, but as he mentioned you'll be setting yourself up for a world of pain.
EAS is really meant for device makers to implement and not normal application development. You should look over the ActiveSync Protocol documentation and look into licensing the protocol (yeah its a pay-for license) and then ask yourself if its worth all the trouble to write all the business logic, ecoding logic, intensive testing and the licensing. An alternative is to use Exchange Web Services (EWS), which might be a much better fit - more rhobust in many areas and no licensing needed.
You should also look at this: http://blogs.msdn.com/b/webdav_101/archive/2011/09/29/new-to-exchange-activesync-development.aspx
I am new to Blackberry app development. I need to call REST webservice from blackberry application using JDE 4.7. I searched but not got any solution. Anyone help pls?
sri
You have to make an HttpConnection request and read the data as an InputStream... have a look at this tutorial Calling REST based web services
I appreciate this an old post - but it has been updated so someone is looking at it, so I thought it appropriate to contribute.
I am sorry, but I can not recommend the code supplied the link from another answer called "Calling REST based web services".
I have made a comment explaining this on the site, along the following lines:
"In my opinion this code is flawed because it does not consider the different connection methods, nor does it consider different encodings. More over it does not consider the Event Thread or provide reasonable error checking and logging. I appreciate that this is just a sample, but I think the author has a responsibility to make people who might use this code aware of how it should be used properly. And this code will cause more problems that it solves. Refer to the supported BlackBerry documentation and web sites for better samples."
Sorry, I am not as familiar as I should be of the questions asked on stackoverflow, but questions like this come up regularly on the BBRY forum here:
http://supportforums.blackberry.com/t5/Java-Development/bd-p/java_dev
I recommend that you go on that forum and type network in the Search box on that site and you be presented with a range of tutorials and KB articles that discuss all aspects of networking. In this particular case I would recommend this:
http://supportforums.blackberry.com/t5/Java-Development/What-Is-Network-API-alternative-for-legacy-OS/ta-p/614822
Networking is not trivial on the BlackBerry, do not expect a cut and paste of the code supplied to work for you. Specifically you should be aware of:
a) The various connection methods, the costs associated with each and the impact that using each might have (e.g. transcoders or caching)
b) The Event Thread, how to get off it and back on when processing a response
c) Logging and reporting so that you can investigate problems when they occur (and they will).
Personally, given that all OS 4.7 devices can be upgraded to OS 5.0 and should be, since OS 5.0 is better, I would forget supporting OS 4.7. Instead look at OS 5.0 and above support and use ConnectionFactory.
I am trying to write a iPhone group chatting/message-board app which will have a backend component. I expect users to register with our system and start posting messages on chatrooms/message-boards. These message-boards can have more than 2 individuals, must support real time notifications and should be accessible from any other clients (like web) as well.
I stumbled upon http://code.google.com/p/xmppframework/ . I realize that XMPP is a very attractive proposition for our needs but I am seriously worried about the infrastructure complexities and scale issues. Besides, XMPP has way too much to offer for my needs. Looks like, XMPP might be the only choice for my pleasure in pain, but I wanted to see what you experts have to say on this.
Any thoughts?
Thanks,
My advice is: whichever protocol you're choosing, do not try to invent your own protocol. Go for XMPP or if you can find an alternative which you find more compelling, use that. Especially if there's already a nice framework for you to use. Why ? Because a single developer new to a field is seldom smarter than a bunch of people with experience ;-) Make use of other peoples' experience by using an established protocol, and make use of existing frameworks to avoid coding mistakes and investing a lot of time to solve a problem yet again that was already solved.
That being said, XMPP is widely deployed and thus would make for a good choice if you later plan to write additional clients for other platforms or want to have third-party clients connect to your server.
Does anyone know of a good code obsfucator for Perl? I'm being ask to look into the option of obsfucating code before releasing it to a client. I know obsfucated code can still be reverse engineered, but that's not our main concern.
Some clients are making small changes to the source code that we give them and it's giving us nightmares when something goes wrong and we have to fix it, or when we release a patch that doesn't work with what they've changed. So the intention is just to make it so that it's difficult for them to make their own changes to the code(they're not supposed to be doing that anyway).
I've been down this road before and it's an absolute nightmare when you have to work on "obfuscated" code because it drives up costs tremendously trying to debug a problem on the client's server when you, the developer, can't read the code. You wind up with "deobfuscators", copying the "real code" to the client's server or any of a number of other issues which just become a real hassle to maintain.
I understand where you're coming from, but it sounds like management has a problem and they're looking to you to implement a chosen solution rather than figuring out what the correct solution is.
In this case, it sounds like it's really a licensing or contractual issue. Let 'em have the code open source, but make it a part of the license that any changes they submit have to come back to you and be approved. When you push out patches, check the md5 sums of all code and if it doesn't match what's expected, they're in license violation and will be charged accordingly (and it should be a far, far higher rate). (I remember one company which let us have the code open source, but made it clear that if we changed anything, we've "bought" the code for $25,000 and they were no longer responsible for any bug fixes or upgrades unless we bought a new license).
Don't. Just don't.
Write it into the contract (or revise the contract if you have to), that you are not responsible for changes they make to the software. If they're f-ing up your code and then expecting you to fix it, you have client problems that aren't going to be solved by obfuscating the code. And if you obfuscate it and they encounter an actual problem, good luck in getting them to accurately report line number, etc., in the bug report.
Please don't do that. If you don't want people to alter your Perl code then put it under an appropriate licence and enforce that licence. If people change your code when you licence says that they shouldn't do that, then it's not your problem when your updates not longer work with their installation.
See perlfaq3's answer to "How Can I hide the source for my Perl programs? for more details.
It would seem your main issue is clients modifying code which then makes it difficult for you to support it. I would suggest you ask for checksums (md5,sha, etc) of their files when they come to you for support, and similarly check files' checksums when patching. For example, you can ask the client to provide the output of a provided program which goes through their install and checksums all the files.
Ultimately they have the code, so they can do whatever they want to it. The best you can do is enforce your licenses and to make sure you only support unmodified code.
In this case obfuscating is the wrong approach.
When you release the code to the client you should keep a copy of the code you send them (either on disk or preferably in your version control as a tag/branch).
Then if your client makes changes you can compare the code they have to the code you sent them and easily spot the changes. After all if they feel the need to make changes there is a problem somewhere and you should fix it in the master codebase.
Another alternative for converting your program into a binary is the free PAR-Packer tool on CPAN. There are even filters for code obfuscation, though as others have said, that's possibly more trouble than it's worth.
I agree with the previous suggestions.
However if you really want to, you can look into PAR and/or Filter::Crypto CPAN modules. You can also use them together.
I used the latter (Filter::Crypto) as a really lightweight form of "protection" when we were shipping our product on optical media. It doesn't "protect" you, but it will stop 90% of the people that want to modify your source files.
This isn't a serious suggestion, however take a look at Acme::Buffy.
It will at least brighten your day!
An alternative to obfuscation is converting your script to a binary using something like ActiveState's Perl Dev Kit.
I am running a Windows O/S and use perl2exe from IndigoSTAR. The resulting .EXE file will be unlikely to be changed on-site.
As others have said, "how do I obfuscate it" is the wrong question. "How do I stop the customer from changing the code" is the right one.
The checksum and contract ideas are good for preventing the "problems" you describe, but if the cost to you is the difficulty of rolling-out upgrades and bug-fixes, how are your clients making changes that don't pass the comprehensive test suite? If they are capable of making these changes (or at least, making a change which expresses what they want the code to do), why not simply make it easy/automated for them to open a support ticket and upload the patch? The customer is always right about what the customer wants (they might not have a clue how to do it "the right way", but that's why they are paying you.)
A better reason to want an obfuscator would be for mass-market desktop deployment where you don't have every customer on a standing contract. In that case, something like PAR -- anything which packs the encryption/obfuscation logic into a compiled binary is the way to go.
As several folks have already said: don't.
It's pretty much implicit, given the nature of the Perl interpreter, that anything you do to obfuscate the Perl must be undoable before Perl gets its hands on it, which means you need to leave the de-obfuscation script/binary lying around where the interpreter (and thus your customer) can find it :)
Fix the real problem: checksums and/or a suitably worded license. And support staff trained to say 'you changed it? we're invoking clause 34b of our license, and that'll be $X,000 before we touch it'....
Also, read why-should-i-use-obfuscation for a more general answer.
I would just invite them into my SVN tree on their own branch so they can provide changes and I can see them and integrate their changes into my development tree.
Don't fight it, embrace it.
As Ovid says, it's a contractual, social problem. If they change the code, they invalidate the warranty. Charge them a lot to fix that, but at the same time, give them a channel where they can suggest changes. Also, look at what they want to change and make that part of the configuration if you can. They have something they want to do, and until you satisfy that, they are going to keep trying to get around you.
In Mastering Perl, I talk a bit about defeating obfucators. Even if you do things like making nonsense variables names and the like, modules such as B::Deparse and B::Deobfuscate, along with Perl tools such as Perl::Tidy, make it pretty easy for the knowledgable and motivated person to get your source. You don't have to worry about the unknowledgable and unmotivated so much because they don't know what to do with the code anyway.
When I talk to managers about this, we go through the normal cost benefit analysis. There is all sorts of stuff you could do, but not much of it costs less than the benefit you get.
Good luck,
Another not serious suggestion is to use Acme::Bleach, it will make your code very clean ;-)