I just came across Google Native Client
Now, it looks really interesting that they ported Quake to run on a Browser and you can run C++ code on a browser to process things more quickly, but I am trying to understand, what is the practical usage of NaCl?
What is the vision behind this by Google? To run software as a service on their "cloud" OS..err browser?
For example: Run Photosphop CS 5 on your browser?!
Anything you can do with ActiveX, but far more secure.
Elaboration:
Google Native Client allows you to run machine code locally and natively, but sandboxed insofar as only allowing access to protected memory regions and disabling exploits in the machine code relating to processor errata (certain sequences of machine code operations which act strangely on particular processors). Additionally, certain APIs are available (such as OpenGL) and there is interprocess communication with Javascript running with the page, allowing webapps which have a fast, powerful native backend.
It would be quite difficult to use the Win32 API to generate any native windows or controls with Google Native Client, whereas it'd be probably a bit easier with ActiveX. However, ActiveX is generally used with things like "Quake Live" to provide a fast, native experience for the player, and additionally for Internet Explorer 'plug-ins' -- the Flash plug-in is ActiveX, for instance, and uses native code (i.e., the plugin is compiled to machine code).
Related
I'am going to communicate EtherCAT master(CX2020) with Linux OS PC(ubuntu) for storing value from PLC on server and writing also.
By EthearCAT network protcol, it should be availave to communicate with windows plc installed twincat.
But I couldn't find the way for Linux.
Is there any solution?
There are various ways for you to communicate with a CX2020 from Linux, it all depends on your requirements and what the usage is for.
Without knowing anything about those, one option is to use the Beckhoff ADS protocol. All Beckhoff PLCs have by default ADS installed on them and you can
(with the right credentials setup for ADS) communicate with the ADS-library. The good thing about ADS is that it is open-source, and thus it's possible to
get the code for Linux.
The ADS sourcecode is available at:
https://github.com/Beckhoff/ADS
You basically need to:
Compile/Install the library on your Linux machine
Create an ADS/AMS-route to your CX2020
Create a program that uses this route to communicate with the PLC
With ADS you can access the variables directly in the CX2020 memory (both read and write!).
There are many finished wrapper libraries available for all common programming languages that you can use directly in Linux. If you're up to Python, I would
recommend checking out PyADS (https://github.com/stlehmann/pyads), which has a good user base and many examples available all around the net.
I am going to implement an easy-to-use and eye-catching graphical user interface for management and configuration of an ethernet switch which has a flash (of just 16 MB) mounted in it, which will have an embedded linux, some specialized softwares, CLI and GUI.
I think, I should go for a web-based graphical user interface so that an admin can access it using the switch's IP. At client side I am thinking of using HTML5 or HTML4 with Javascript as GUI developed in Flex will probably take much more flash space.
However, I don't have a clear idea of server side technology to be used. Should I go for mini-apache for embedded systems with PHP (as I am familiar with Apache+PHP on x86 systems)? or is there a better alternative?
Also, should I go for a MVC type of architecture? Are there some great MVC frameworks developed for embedded systems?
Update:
Basically, I only need to provide a GUI on top of a CLI running on switch. Basic workflow of the application will be something like:
User access GUI through a web interface
User performs an action on GUI
A CLI command corresponding to the action performed is sent to the
server (running on switch)
Server runs the CLI command on the switch
Server returns result of the command back to GUI
You could use an HTTP server library like Onion (in C), GNU libmicrohttpd (in C), or Wt (in C++) to make your own specialized HTTP server (embedded inside your device).
You could also use Ocsigen in Ocaml for the same purpose.
I don't think that embarking a complete HTTP server (apache, or perhaps better lighttpd) with a PHP stack makes real sense on an embedded device (the code stack would be much bigger). On such a device the performance does not matter much (you won't get thousands of HTTP requests per second), but the code space (and process space, ie memory consumption) is quite important. (And the specialized web server solution I am suggesting uses only compiled code, which would run faster than interpreted PHP).
If you insist on having a lighttpd or apache web server in your device -which I believe is wrong-, you could make your application a FastCGI application (and code it in C, C++, Ocaml, ...).
As Simon Richter commented, you could consider making it (also) an SNMP service.
I wanted to write a B/S project that client side uses ActiveX or Gecko to Communication with server via network socket. And any browser(ie/firefox/chrome/opera/safari) can use it.
If you want to support every major browser than you need to write both the ActiveX part (for IE) and the NPAPI part (for all other browsers). You can use support both technologies with one DLL though.
An easier way than implementing both yourself would be to use FireBreath, which does that for you and provides an abstraction layer over those APIs.
As you write native code with both technologies, sockets etc. can be used with both. The biggest limitations are with the UI side and permissions due to running code in a host application.
Note that XPCOM as a plugin technology is obsolete.
Note: There is a similar question called 'installing nodejs on windows machine'.
And various answers explaining how by installing cygwin you can get it working there.
now, I don't want to install cygwin.
I just wish I could run nodejs on a windows box.
I want a "nodejs.exe" to kick off.
Can somebody explain to me
1) why nodejs has not been ported on windows - what are the technical reasons for not providing an exe ?
2) are there any plans to have nodejs on windows ?
I really would like to use it but I can't accept that I have to accept cygwin.
That's just not right.
Update:
For optimum node on windows development I recommend you use the Windows Azure powershell for node.js. It's a powershell optimised for using node, npm and the azure APIs. (the azure apis are optional. I would still use this powershell if I didn't use azure).
When : v0.6
Currently you can get a binary file that (kind of) works under windows. Go ask on the node.js IRC channel. They'll hook you up.
Basically if you read up on node.js road plans you will find that proper windows support is planned for 0.6, we are currently on v0.4.7 and the v0.5.x beta is in full storm.
I won't give an ETA but it's soon.
IRC can be found at the Community links
PDF showing v0.6 road plan
July 2011 update:
#nodejs v0.5.1 is the first to ship with an official Windows executable. We're hoping to get some good feedback.
Microsoft has officially gotten involved with joyent in making node.js run natively on windows.
Running Node under Windows presents several technical problems, mostly related to how Windows' internal design differs from that of Linux and the "change in mindset" required to port Unix applications to Windows.
Background
Linux was designed to be a replacement for Unix, a well-known multitasking operating system, so from day one it has been a multi-user/multi-process, server-oriented operating system. The idea of multiple processes sharing system resources is key to its internal design.
Windows was initially designed as a single-user/single-process desktop operating system and so did not support shared access to system resources. In 1993 Microsoft released a newly redesigned version of Windows--called Windows/NT--to better support the shared resource, multitasking model required by servers, but due to its existing installed base of users, Microsoft required NT to also support all the features of its single-user/single-tasking forebearer.
Windows 7 is a direct descendant of NT and Microsoft's need to support legacy users continues to this day (and in the opinion of many, has severely muddled Windows' internal design.)
Further, Microsoft hired a systems architect named Dave Cutler to design NT. Dave is best known for designing a competitor to Unix called VMS, the internal design of which differs significantly from that of Linux, which has caused a lot of problems for developers interested in porting their Unix programs to Windows.
The clearest example of this "impedance mismatch" between the internal design of Windows and Linux is how they handle event-driven, non-blocking input/output (io) on which Node relies to perform its (apparent) multitasking magic in a single thread of operation.
Linux supports two system-level functions called select() and epoll() which can be used to asynchronously inform a process of changes within the operating system that affect it. Node relies heavily on these functions but Windows doesn't support either, relying instead on "Change Notifications" (mostly) to handle event-driven io.
Is it possible to write a mobile application with J2ME and whenever we want to implement a functionality not offered by J2ME call native mobile API ? (kind of like what is done with .NET, whenever you need something not provided, you just call the Win32 API from the .NET platform).
While JNI is not officially supported in J2ME, the Symbian implementation of J2ME obviously uses something very similar.
Since most J2ME APIs have a corresponding Symbian OS C++ API, what Symbian did (a lot) is develop adaptation layers between the 2.
Between that and the new modular architecture of the IBM J9 virtual machine (from Series60 3rd edition feature pack 2 onward), it is technically possible to add a new API to the virtual machine without actually needing to recompile most of a handset firmware.
However, third party developers simply are not allowed to do it without a lot of help from the handset manufacturer.
A loopback socket connection is the solution that people have tipically implemented to transfer data accross the language barrier. Large-scale deployment is not the easiest task, though, as you technically need to install 2 applications on the device. Once you understand the threading model of the Symbian J2ME implementation, you also realize how ugly and inefficient a hack it is.
When you reach that kind of issue, it's time to learn Symbian OS C++ and do it right.
No. That's not possible with Java ME.
Only sort of. Actually it is possible but not directly. You can write a native server that listens on a local socket and send requests to it from your Java MIDlet. Someone even released a framework to do this called MIDP-JNI (as opposed to real JNI). Obviously the form of the solution imposes some limitations on what you can do with it but it isn't actually impossible.
Be aware that using this approach can make your application much more complex to debug.
If you are specifically looking out for Nokia/Symbian, then APIBridge http://wiki.forum.nokia.com/index.php/J2ME_API_Bridge_Interface could be a solution. Typically it is the 'official' version of 'native server on local socket' kind of thing. The APIBridge is 'extensible' & you can write your own 'plugins' for your suitable 'low-level' task.