There is a javascript code residing in my Android app's webkit container. This code makes use of WebSockets to communicate with the server. The same JS code works in other platforms such as iOS, but in Android 2.3, it doesn't. I read somewhere that the webkit in Android does not support WebSockets, and support will come only in Jelly Bean onwards.
In view of this, I need to provide a wrapper from the native layer (in Java) making use of plain sockets. From the little I know about sockets, it seems straightforward to support the usual APIs such as open(), send(), receive(), etc.
Is there anything else I need to know that the WebSocket protocol needs, which I will need to provide from the wrapper code? After all, the server talks to the client (my android app) as if it is a WebSocket, and not a native socket.
Some notes to consider: a) I cannot make use of any third-party library - it will have to be developed in-house. b) There will not be any binary data transferred; only text.
Thanks,
Rajath
Websockets are not raw sockets, they require an initial handshake then simple per-message framing. See the protocol spec for details. The sections on handshake and data framing will be most relevant.
I know you said you can't use third party libraries but be aware that projects like Java-Websocket might be interesting to you. It's liberally licensed so suitable for inclusion in any closed source app. Or you might find it useful as a reference while debugging your own code.
Related
I have a question regarding the (relaxed) browser security of app.js as i have read somewhere in documentation (i tried searching for it but could not find it). I do see that there is an option that can be set here:
https://github.com/appjs/appjs/blob/master/docs/index.md
I have started building a desktop application using adobe AIR using Starling and Feathers UI because the service i am building the app for (Pinboard) does not have CORS enabled and will not do so in the future (see this google group chat about it). However, i would like to start with (node-webkit / App.js / similar HTML5 desktop framework) as well, just to see how that goes (and also i believe that building good transitional interfaces is a lot easier and faster in HTML5 nowadays).
My generalized question is: will app.js and other HTML5 desktop application frameworks allow me to circumvent CORS requirements? I am trying to find more concrete information about the browser security settings but i can not find it. Any pointer to such information (of different desktop application frameworks) will be greatly appreciated!
Michael
On the "server" side of your app, you are running Node.js, which does not enforce any CORS restrictions. That's a browser thing, Node.js is just a JavaScript runtime.
On the client side of your app though, you might suffer from CORS, that depends on the runtime/framework and I couldn't find anything about App.js either. But you could simply proxy requests to Pinboard through the server side, which would work around all CORS issues. There are a quite a few proxy servers for Node.js that could be used for this purpose, like node-http-proxy.
I have an embedded system which is running the LwIP server(v1.2), I need to be able to stream a data array into the javascript on the client side? I'm looking at using chrome and some HTML5 features, so some people have suggested using websockets. Does anyone know where I need to start to use these with the LwIP framework? Any help at all would be much appreciated!
WebSockets is a relatively simple protocol so you could use the protocol spec and write your own server. Since lwIP offers a bsd sockets API, you could also search for existing open source C servers. (A quick search shows up this candidate for instance. BTW, note that this code licensed as GPL. You should only use it if you understand the requirements using GPL'd code puts on your project.)
Note that while Chrome support for websockets is good, support is patchier if you later decide to use other browsers (and particularly to allow users with older browsers). See here for details. If support for a variety of browsers matters to you, you'll probably have to include code in client and server to fallback to long polling when a websocket handshake fails.
I need to deal with breaking connections and other standard things which are not handled by WebSockets yet. Something tells me that there must be plenty of plugins to do this. Do you use anything like that or write your own routines?
I need it for the client side, since I use Sinatra on the server side.
There are two common issues at hand: supporting older browsers that don't natively support WebSockets and automatic reconnect (in case of breaking connections).
Older browsers are supported by several vendors and products through emulation using different transports - what you need to look at is how good the emulation is. Here's a brief article on the topic describing the problem and Kaazing's solution [disclaimer: I work for Kaazing].
The Kaazing WebSocket Gateway also provides automatic reconnect - in case the connection breaks.
You can download the free developer version of the Kaazing Gateway - to give it a try.
I am trying to create an ActiveXObject (to use FileSystemObject) but it's only supported in IE.
Is there a way I can make it work in Chrome or Firefox? I need to read all the files in a specific given folder, and list those.
Well, is there another way to do it?
ActiveX is only supported by IE - the other browsers use a plugin architecture called NPAPI. However, there's a cross-browser plugin framework called Firebreath that you might find useful.
No for the moment.
I doubt it will be possible for the future for ActiveX support will be discontinued in near future (as MS stated).
Look here about HTML Object tag, but not anything will be accepted. You should try.
ActiveX resolved in Chrome!
Hello all this is not the solution but the successful workaround and I have implemented as well.
This required some implementation on client machine as well that why is most suitable for intranet environment and not recommended for public sites. Even though one can implement it for public sites as well the only problem is end user has to download/implement solution.
Lets understand the key problem
Chrome cannot communicate with ActiceX
Solution: Since Chorme cannot communicate with ActiveX but still it can communicate with the API hosted on the client machine. So develop API using .Net MVC or any other technology so that through Ajax call it can communicate with the API and API communicate with the ActiveX object situated on the client machine. Since API also resides in Client machine that why there is no problem in communication. This API works as mediator between Chrome browser and ActiveX.
During API implementation you might encounter CORS issues, Use JSONP to deal with it.
Pictorial view of the solution
Other solution : Use URI Scheme like MailTo: or MS-Word to deal with outlook and word application. If your requirement is different then you can implement your customized URI Scheme.
ActiveX is supported by Chrome.
Chrome check parameters defined in : control panel/Internet option/Security.
Nevertheless,if it's possible to define four different area with IE, Chrome only check "Internet" area.
Is it possible to communicate over a machine's serial port through JavaScript?
I have to write a short program that sends data to a microcontroller over the serial port that has a GUI and is cross-platform compatible, and I really don't want to use Java's Swing.
JavaScript itself doesn't have any built in functionality to allow you to access the serial port. However, various JavaScript engines (v8, rhino, etc) allow you to write your own custom native objects.
You might want to check out node.js, which is a JavaScript library for v8 that's focused on writing server-side code (rather than web browser client code). It seems that someone's already written a serialport package for that:
https://github.com/voodootikigod/node-serialport
This is an old question, but in case this helps anyone else, Chrome Apps have access to a serial API - http://developer.chrome.com/apps/serial.html - which might help.
It's Chrome specific (obviously..), but Chrome is available cross-platform so might answer the question.
There's a cross platform plugin for serial port communication called jUART.
Yes, it's possible using an ActiveX(I did it). You can make an activeX and use JavaScript to invoke it.
If you prefer, you can make a .net dll and register it using regasm. Take a look at this link
You also can write an activeX using VB6 and register it. Both works fine.
Ps.: if you are using ActiveX, the JavaScript code will run just on IE.
If you have a DLL library (this includes e.g. most Windows APIs) that allows you to communicate over serial port you can invoke it from Firefox chrome code (or content code with universalxpconnect privileges) by using ctypes.
What you could do is to use a Java applet that connects to the local computer's Java application that reads the serial port. The applet would then transfer the data to a JavaScript class or something that can hold the information. Then additional JavaScript code can be used to access the data. It's a complicated solution but should work.
Another way is to create a POJO service.