I want to execute some javascript that will send a string of text to a c++/java console application running on the same machine as the web browser
What javascript should I execute? and how should I receive the string?
As far as I know, there are two ways to transmit data to somewhere else using JavaScript. The first is using an XMLHttpRequest, the second is using a WebSocket. In both cases, the JavaScript code will establish a connection to another program, which in this case you want to be your C++/Java program.
In the first case, if you want to communicate using an XMLHttpRequest (or other libraries that use this, such as jQuery's get or post), you'd need to make sure that your C++/Java application starts a small webserver. This way, the JavaScript code can establish a connection to it and send data. I'm sure there are C++/Java libraries which you can use for this, but even if you can't it should be fairly simple to get something to work with just plain socket code. The text-based HTTP protocol that you need for this is not that difficult.
In the second case, you'd need to make sure that a WebSocket server is started in your C++/Java application. Your JavaScript code then can connect to this server and just send its data. I'm not that familiar with the WebSocket protocol but I suspect that it's slightly less trivial, so using a library for this would be a good choice.
Related
I have a C++ project for windows, using MiniBlink as embedded browser. (MiniBlink is a smaller Blink, which is close to chromium). I use this embedded browser to show responsive and nice looking dialogs with Quasar.js (wrapper for vue.js).
Problem:
Mostly a browser is just the passive backend. In my case, both the backend (project with embedded browser) and the frontend (dialog) are active and thus I need some communication. At the moment I use a local server to catch HTTP send from the frontend to the backend.
But is there a way to communicate from the backend to the frontend? At the moment I could only think about catching cookies or using a permanent loop in JS to send http queries to check for a possible response.
And is there no other way to send information to a backend? Everything is local, I dont need nor really want to send it into the network.
Thanks!
Idea 1: Use a local temp file to save on one side and read on other (can be also used both way)
Idea 2 (similar to question author solution): Local server with both side communication (GET/POST request into one side, text/json other way around)
Idea 3: Use launch parameter to pass though data directly into links for example: instead of using browserprocess.exe file.html, use browserprocess.exe file.html#showsomething
There are also other ways which like catching for example: checking window title of process with certain binary name from running tasks by other side; we didin't get good enough info about your background becouse you coud either use it in same process or other process, if thats same process you coud also just directly use variables both ways directly in code of miniblink and do action when they meet if statement
As CertainPerformance added as a comment, WebSockets might be the best way to go.
If one does not like to implement a websocket server, because a http server is already running, long polling requests might be the best workaround to simulate this behaviour.
Long polling: The client sends a request, which stays open as long as possible. If the server needs to communicate, it can use the open request to send its own "request" via response. It is a bit hacky, but essentially the idea behind websockets.
Mozilla has a nice article to help with websockets:
https://developer.mozilla.org/en-US/docs/Web/API/WebSockets_API/Writing_WebSocket_servers
If you (like me) use vuejs or quasar, you might want have a look at vue-native-websocket.
https://github.com/nathantsoi/vue-native-websocket
Good luck
I am currently designing a GUI for a piece of hardware. We want the GUI to be able to be accessed over a browser. The browser would be displaying a map generated from C++ code, but I also need to send some params to the code that generates the map from buttons on the JS front end? Is there anyway to accomplish this. I have done a little research so far and know about web sockets and AJAX, but I am not entirely sure it is what I am looking for. In an ideal world I would be able to just send UDP packets, but my research tells me that is not possible, not is TCP. Is this correct?
Thank's in advance for any help!
Your C++ code could setup a server that listens for requests. You could use libhttpserver, for example. Then, in your JavaScript code, you can use XMLHttpRequest or the Fetch API (for newer browsers) to make an HTTP request to the server, which would then return a new static page (with the generated map embedded into the page).
im trying to create a simple website with HTML/CSS and Javascript. Basically the user should be able to input a number into a textfield and "send it" with a button. When the button got pressed i want to run a Javascript function that searches the number in a sql database.
Creating all that stuff shouldnt be a big problem for me, but i have no clue how to create a safe connection between JS and SQL. I have read that a direct connection with javascript is very insecure.
Some people recommend to use java or c# to built an sql connection. How would that work? Basically just an Javascript code, that runs an java/c# application(which builds an sql connection) and returns the needed sql data?
Also heard that its possible to create a sql connection with node.js, is this safe? Or is another method more suitable?
Greetings
I have read that a direct connection with javascript is very insecure
The danger is in giving direct access to your database to the client. JavaScript is most commonly run client-side in web browsers, so for it to access the database you would have to give the browser (and thus the visitor) a username and password on your database server and let them run raw SQL.
There are many possible security risks with this and it just isn't worth it.
(Aside: You can't make arbitrary socket connections with browser-side JavaScript, so it's impossible to connect to most database servers from it anyway).
If you want to expose data to JavaScript running in the web browser, then the standard approach is to write a webservice.
You can write the webservice in any programming language you like (including JavaScript). It listens for HTTP requests, reads data out of them, possibly performs authn/authz, the queries the database (applying the well-documented defences against SQL Injection attacks) and returns the result (often formatted as JSON).
The client-side JavaScript, therefore, just has to make an HTTP request (e.g. with XMLHttpRequest or fetch) with parameters passed in the query string or request body, and process the data it gets back from it.
Connecting to a database using client side javascript is very insecure as the javascript will need to know the login details. And since the client side javascript is on the client side, any user will be able to see the login details in plain text.
The best way to do this is to make a webservice on a server. When the button is clicked it will make a GET/POST request to the webservice with the entered number as a parameter. The webservice, which can be made using any language pretty much, will create the connection with the database and insert the row itself.
Although I would advise going the webservice route since it will be much easier to make secure. Playing with javascript to database is extremely dangerous unless you have a really good system and understand exactly what you are doing; but if you really want to do it and have an application that requires it, then can use PouchDB connected with CouchDB.
PouchDB is run locally and can sync with CouchDB over HTTP.
https://pouchdb.com/
https://couchdb.apache.org/
There is an answer here discussing basic security with pouchDb synchronizing with couchDb. Basically, each person needs separate login credentials and credentials should never be stored in the page code.
PouchDB security
There are some neat uses for pouchDB: https://pouchdb.com/users.html
Suppose I have server. A client loading an HTML file containing a javascript library will have the script executed by the browser. The problem here is that if the client's computer is slow, the processing will take a long time.
So I want to move the processing to the server side. But, instead of having to rewrite the entire javascript library into another language, I simply want to run the javascript on the server.
Googling "server side javascript" directs me to Node.JS, which in my imagination have the capability to do so. But, I cannot find a tutorial which does just that. Does this mean that there really is no easy way to do so? For example, because the javascript script may contain DOM specific things such as document.getElementById(), which does not make much sense on the server side.
There is no trivial way to simply shift processing of JS from the client to the server.
You need to break the code down into code that must run on the browser (such as, assuming you don't want the browser to load an entirely new page, DOM manipulation) and code that can run on the server.
Then you need to provide a way to pass data between the server and the browser, this is normally done via HTTP (using Ajax).
When you take input from the client you need to send it to the server in an HTTP request (instead of just passing it as an argument to a function). The server needs to read the HTTP request, process it, and make an HTTP response.
The Ajax callback then needs to parse the response and run any client side logic (such as DOM updates) in response.
Note that network communication times will impact performance.
You can't "merge" the client and server in this way. All you could do is process the data on the server and just display it in the client without any further processing. Maybe you should refresh you knowledge about HTTP and how websites are send to the clients. Without any additional tricks, like websockets, comet or ajax polling, you can't access the client after you send the initial website to it. Even than you can just send data to the client.
When you want to stick to Javascript, Node.js is a good option. But even than you would need to send the data you want processed to the server, process it there and send back the processed data in JSON or "display ready" HTML.
I am new in JavaScript, and now I want to run a Linux application in JavaScript and show the result in a web page. It all happens in client without a server. But for security issues or something else, JavaScript as no such interfaces. I know in Windows, it could be achieved with activeX, but how could I achieve this in Linux?
I just wanna make js+browser equal to a client application without the complex GUI design. So there is no server. Any easy way to accomplish it?
Maybe Node-webkit is what you want.
It allows you to easily create a desktop application in javascript and access "low-level" stuff so you can run commands, without the need of an http server.
Can't be done.
JavaScript cannot interact with the users system in any way.
The only thing you can do is send a request to a server, which executes the command and sends the response back.
With javascript alone can't be done. But you have at least two option to do this using javascript plus other technologies.
The first one is what Jivings sent, using Jquery to sent a post request to a scripting language at the server side.
The second way is to install Node.js. This platform runs on javascript engine, and has all the features you need from the language. After installing it just see this post that explains how to execute a command.