I'm not sure which technology I should be using, or even what exactly I'm trying to do is called, so I was hoping to just get some guidance on the issue.
We have a client/server architecture, and from the client side you should be able to send a command to the server side either by going from Browser -> Client -> Server, or just directly from Browser -> Server
My question is, what should I be looking in to to help me accomplish this task? I believe if I were to use a Chrome Extension, it would have to use NPAPI to interact locally with my PC, which is less than recommended ;)
The solution only needs to work on Windows, and will not be accessing any of the local users files.
Thanks for your help!
Within Chrome Extensions, you are allowed to access external resources if and only if you explicitly define the permissions (url pattern) in the manifest file.
Depending on the need of your application, you could use RESTful server approach or WebSockets server approach. Once you finish developing your server, your extension can communicate through it using existing web technologies (XmlHTTPRequest, WebSocket).
Assuming your going to use RESTful, what I would do is create a JavaScript service class/library that communicates to your backend (Server) using XHR, and include that in your background page within the extension. Then you can use Extension Message Passing to communicate to your service class.
Think of it as this, the scripts defined in the background context within your extension lives in between your extension and your server, acting like a facade. Search on GitHub/StackOverflow if you need questions regarding how, there are many useful posts/projects.
Related
I have to create a little AJAX chat in my web application and I'm dealing with problem of real-time communication between JavaScript client and PHP server.
I want my js client to be able to catch new messages from the server as quick as possible. My first idea was to create AJAX request for example each 5 sec. to see whether there are new messages.
However, I'm not sure what happens if my application use for example 1000 people, it must be huge load to Apache httpd.
I also know about technique called 'long-polling' request, but when I tried that locally on my server, I've completely shooted down my Apache (I've read sth about problems with apache and long-polling). The next way I know about is WebSocket.
However, is it true that I have to be able to open port on webserver to use it? Because on regular web hosting, I thing it's not possible and I cant change any Apache/PHP settings on my hosting.
Do you have any suggestions how to solve it?
If you want to use websockets, you better have full control over your server as you may be facing the need to start and stop the websocket daemon whenever it's needed.
I wouldn't recommend using "regular web hosting" because of its restrictions.
I think that you are looking for "virtual server providers", that provides you full control over the server you manage. You should look at Amazon Web Services. There are many others that you may find.
I need to deploy an application onto some Windows machines for purposes of data collection from a group of people (i.e. the application will be used to gather responses to a series of survey questions). The process is interactive, alternating between displays of text and images with specific timing requirements. I have put together a prototype application using HTML and JavaScript that implements the survey. However, there are some unique constraints on the deployment environment that have me stuck:
While the machine is Internet-connected, the client requires that the survey application must run fully local to the PC that it runs on. Therefore, sending the survey results to a remote server is not permissible. Obviously, saving to a local file from a Web browser is typically not permitted for security reasons.
Installation of applications onto the machines that will run the survey is not permitted.
The configuration of the machines is not known specifically a priori, but I can assume some recent version of Windows with IE8+.
The "no remote access" requirement was a late comer, and has thrown a wrench into the plan of just writing a simple Web application that could post results to an HTTP server. I'm now looking for the easiest way forward. Two main approaches come to mind:
Use a GUI framework that provides a control that can display HTML/JavaScript; running a full-blown application on the PC would allow me to save the results to the filesystem. I've never done this, but it seems like in this day and age it shouldn't be too difficult. This would allow me to reuse much of my existing prototype implementation, but I would need some way of transferring the results (which would be stored in a JavaScript data structure) outside of the Web control to where the rest of the application could access it.
Reimplement the entire application using some GUI framework (I've used PyQt successfully before, although not on Windows). This approach is obviously less desirable than #1 due to the lack of reuse. However, it may be necessary if #1 isn't feasible.
Any recommendations for the best way to go? Ideally, I'm looking for a solution that can be run in a "portable" manner from a USB thumbdrive or similar.
Have you looked at HTML Applications (HTA)? They work in IE5+ and can use Windows Scripting Host to write to local drives and UNC shares...
Maybe you can use a portable web server with a scripting language on the server side. http://code.google.com/p/mongoose/ Mongoose, for example, you can run PHP, CGI, etc. .. scripts. Then, simply create a script to save a file to your hard drive. And let the rest of the application in the same manner.
Use a script to start the web server, and perhaps a portable web browser like K-Meleon to start the application http://kmeleon.sourceforge.net/ This is highly configurable. Or start the system explorer to your localhost URL.
The only problem may be that the user has to modify the firewall for the first time you run the server?
I am really confused at to how Meteor works.
I know there's a server side where you just install it using the terminal.
But what about the client?
Does the client need to install anything?
For example, clients need to install Adobe Flash to run Flash. Are we talking about the same thing here? Or can the client just access it through a regular page without installing anything.
Thanks for the clarification.
<3 StackOverflow
Meteor is a pure javascript web-application framework.
All you need to run meteor is a JavaScript environment.
Server-side, NodeJS is the gold standard javascript environment.
Client-side, all you need is a browser that supports javascript.
There are no plugins required or other magic at work. It's just javascript.
I am assuming you mean the Meteor Http Server? In this case, you can think of it as being very similar to SignalR or node.js. Basically javascript on the client handles receiving events that come back from the server, so you will generally need to include a script on the client side.
You may want to read the following links for more information.
http://meteorserver.org/browser-techniques/
http://www.hanselman.com/blog/AsynchronousScalableWebApplicationsWithRealtimePersistentLongrunningConnectionsWithSignalR.aspx
I think the question refers to http://meteor.com, and if that is the case the client does not need to install anything.
Meteor is a framework for writing Javascript applications, and as such all modern browsers support it "out of the box". The initial request for a web site will download the HTML, CSS and Javascript and it will run just as any other web application like GMail, etc.
You can check out a series of example applications at http://madewith.meteor.com and you should be able to run them without adding any plugins, etc.
I need a simple way to use XMLHttpRequest as a way for a web client to access applications in an embedded device. I'm getting confused trying to figure out how to make something thin and light that handles the XMLHttpRequests coming to the web server and can translate those to application calls.
The situation:
The web client using Ajax (ExtJS specifically) needs to send and receive asynchronously to an existing embedded application. This isn't just to have a thick client/thin server, the client needs to run background checking on the application status.
The application can expose a socket interface, with a known set of commands, events, and configuration values. Configuration could probably be transmitted as XML since it comes from a SQLite database.
In between the client and app is a lighttpd web server running something that somehow handles the translation. This something is the problem.
What I think I want:
Lighttpd can use FastCGI to route all XMLHttpRequest to an external process. This process will understand HTML/XML, and translate between that and the application's language. It will have custom logic to simulate pushing notifications to the client (receive XMLHttpRequest, don't respond until the next notification is available).
C/C++. I'd really like to avoid installing Java/PHP/Perl on an embedded device. So I'll need more low level understanding.
How do I do this?
Are there good C++ libraries for interpreting the CGI headers and HTML so that I don't have to do any syntax processing, I can just deal with the request/response contents?
Are there any good references to exactly what goes on, server side, when handling the XMLHttpRequest and CGI interfaces?
Is there any package that does most of this job already, or will I have to build the non-HTTP/CGI stuff from scratch?
If I understand correctly, the way I approach this problem would be a 3-tier (Don't get hang up so much on the 3-tier buzz words that we all have heard about):
JavaScript (ExtJs) on browsers talks HTTP, Ajax using XmlHttpRequest, raw (naked) or wrapper doesn't really matter, to the web server (Lighttpd, Apache, ...).
Since the app on the embedded device can talk by socket, the web server would use socket to talk to the embedded device.
You can decide to put more business logic on the JavaScript, and keep the Apache/Lighttpd code really thin so it wont timeout.
In this way, you can leverage all technologies that you're already familiar with. Ajax between tier 1 and 2 is nothing new, and use socket between 2 and 3.
I did not mean that you did not know socket. I just proposed a way to take a desc of a problem where I hear a lots of words: XML/HTML/Ajax/XmlHttpRequest/Java/PHP/Perl/C++/CGI and more and offer a way to simplify into smaller, better understood problem. Let me clarify:
If you want to ultimately retrieve data from the embedded devices and render on the browsers, then have the browsers making a request to the web server, the web server uses socket to talk to the embedded device. How the data is passed between browser and server, that's normal HTTP, no more, no less. Same thing between web server and embedded device, except socket instead of HTTP.
So if just you take a simple problem, like doing an addition of 2 numbers. Except these 2 input numbers would get passed to the web server, and then the web server passes to the embedded device, where the addition is carried out. The result gets passed back to the web server, back to the browser for rendering. If you can do that much, you can already make the data flow everywhere you want to.
How to parse the data depends on how you design the structure of the data that might include container which wraps around a payload.
"... whatever HTTP is coming to the server into usable bits of information, and generate the proper HTTP response"
...but that's not any different than how you handle the HTTP request on the server using your server-side language.
...how to implement a backend process in C/C++, instead of installing a package like PHP
If the embedded device is programmed in C/C++, you are required to know how to do socket programming in C/C++. On your web server, you also have to know how to socket programming, except that will be in that server-side language.
Hope this helps.
I've always wanted a way to make a socket connection to a server and allow the server to manipulate the page DOM. For example, this could be used in a stock quotes page, so the server can push new quotes as they become available.
I know this is a classic limitation (feature?) of HTTP's request/response protocol, but I think this could be implemented as a Firefox plugin (cross-browser compatibility is not important for my application). Java/Flash solutions are not acceptable, because (as far as i know) they live in a box and can't interact with the DOM.
Can anyone confirm whether this is within the ability of a Firefox plugin? Has someone already created this or something similar?
You may want to look at Comet which is a fancy name for a long running HTTP connection where the server can push updates to the page.
It should be possible. I have developed a xulrunner application that connects to a TCP server using sockets. Extension development would likely have the same capabilities. I used a library from mozdev - JSLib. Specifically check out the networking code. The fact that there is a Firefox add-on for JSlib add-on for Firefox makes more more confident.
Essentially, as I understand it, sockets are not part of JavaScript, but through XPCOM, you can get raw socket access like you would in any c/c++ application.
Warning: JSLib doesn't seem to receive a lot of attention and the mailing list is pretty sparse.
Java/Flash solutions are not acceptable, because (as far as i know)
they live in a box and can't interact with the DOM.
That's not actually true of Java. You can interact with Java via JavaScript and make DOM changes.
http://stephengware.com/proj/javasocketbridge/
In this example there are two JavaScript methods for interaction
Send:
socket_send("This was sent via the socket\n\n");
Receive:
on_socket_get(message){ more_code(message); }
You may want to look at Comet
a.k.a. server push. This does not let the server "update" the client page directly, but all the new data is sent to the page through a single connection.
Of course, a Firefox extension (as well as plugins, which are binary libraries that can do whatever any other application can do) can work with sockets too. See 1, 2.