I am using nodeJs and the express, express-handlebars and mqtt packages.
I am recently trying to update a table which shows the content of the current temperature outside and inside. This table is only a part of the website making it worth striving to just update this particular talbe each second.
Therefore, using does not seem like the right answer for me and also harms the ability to set settings and click on a link.
I have already tried using the Query .load function which indeed works but does not work properly together with express-handelbars. Instead of the content transmitted to my server via MQTT, {{temperatureInside}} and {{temperatureOutside}} is shown on the website.
Any ideas how to solve this problem?
In the case that you want the table to be updated automatically, that means you need the server to tell the front end that there is new data. This is not possible with standard HTTP requests, which is why some clever person built Websockets (WSS protocol). Using Node, a the library I use for this is socket.io
socket.io has code that needs to be both imported on the front end (tells your client how to talk through WSS) and required on the Node side (npm install socket.io --save)
From there, you can set up custom events that both your server and client understand. I'll leave you to go through the docs, but socket.io would certainly do the trick for you. I've used it in many similar circumstances.
Related
I've developed an application that I would like to use meteor.js for real time updates (I want to enhance but not change my program, for example when a user adds a comments make it update in real-time ) . Problem is meteor.js uses node.js (so javascript as server-side code). I use LAMP stack, Is it possible to get PHP to feed data into meteor.js from mysql.
Meteor is more than just an 'interactive webapplication'-builder or javascript framework. The idea is to have only one programming language (besides HTML/CSS for markup) to do all the work. Basically it creates a 'remote server' (in the clients browser) it can push data to and at the same time it publishes various API's to the users system. The data passed through these API's / connections has a specific structure which has to be adhered at all time.
Meteor is built around NodeJS, which makes it hard (if not impossible) to run it without this backend. Sure you can try to mimic the backend using PHP, but it would be a waste of time. Reading your question you'll be better of using a javascript framework like jQuery or Prototype. Unlike Meteor you will need to do the AJAX calls (POST & CallBack) yourself, but you can actually decide which backend you want to use yourself (including PHP / MySQL).
If you want to do this anyway you need to check the Meteor & NodeJS source code to see what the minimum requirements are to make Meteor run under PHP. The PHP stack has to interpret the commands Meteor sends and receivers, but this won't be an easy task.
You can use comet (or reverse ajax) for realtime updates.
Trying to marry node.js with PHP doesn't sound like a worthwhile path to go down. If someone insisted on using a system like Meteor.js, yet with a PHP back-end, it would make more sense to look at AngularJS which is mainly the client side.
Of course, that is different technology stack. If someone really insisted on the blending, one could consider using server side sockets to interact with PHP Web services; and/or use mongodb and/or mysql-node to interact with the same databases.
I released a meteorite package that interacts with a Wordpress site that has the Wordpress JSON API. A quick fix. For now.
Comes with a backend call that will return the raw data, or a publication that stores the posts using their id's instead of a randomly generated mongoid. And some basic templates to get you started including a Session variable that keeps track of the currently selected post.
I'm working on it a lot more and will eventually have a version that directly makes mysql calls from node so you won't need php or Wordpress; just the ability to access the mysql database (which can be remote, with the appropriate configuration, or on the same machine).
Currently I have a Flask server that runs a small web frontend as well as a command line interface to that same server. The basic idea looks like this:
<Top section: allows file upload>
* list of files from database
<Second section: allows file manipulation/ upload>
* list of files from database
<Third section: Not files, but still allows for database changes>
* list of things made from database
Now this works well from the front end, but currently if the CLI or another client makes a change to the database, it doesn't update other clients. I have it somewhat working with JS polling and rewriting the list of files every 10s, but that seems both inefficient and also would look very messy if I had to do it for every section. I saw websockets mentioned in various forums, but I've never used them and am unsure if it would be a pain to add. I'm not trying to rewrite the whole thing for a single feature.
Final takeaway: How to update all clients better than polling/ how to do polling efficiently?
Yes you are correct. You need sockets. There are bunch of articles over the internet but I would like to give a summary and try to explain why sockets will be the best fit to your requirements.
Sockets are way of achieving two way communication between client and server without the need of polling.
There is a package called Flask-SocketIO
Flask-SocketIO gives Flask applications access to low latency
bi-directional communications between the clients and the server.
Then for the scenario where you would like to send changes to all the connected client when one client does some work to your database or something similar, you will need to use broadcasting. When a message is sent with the broadcast option enabled, all clients connected to the namespace receive it, including the sender. Here you can find details of the broadcasting using Flask-SocketIO.
I am working on a home automation hub -- a Raspberry Pi running locally that displays weather info, controls my lights, etc. It is "networked" (and I use that term loosely) to a website via a shared MongoDB. Both the site and the hub are running Node.js/Express servers.
Essentially, I am looking to be able to enter text into a field on my website and then display it on my hub.
I'm struggling to figure out how to pass data between them. I can think of a couple ways that might get it done, but the only way I know I could get working is to implement some sort of Mongo watcher/listener to watch for changes on a specific collection. Essentially, you enter the text into the site, that updates the document in Mongo, the watcher informs the locally-running hub, which then fetches and displays the new content.
This seems hacky. Is there a better way? Is this something socket.io could manage? Maybe I'm overthinking it? Help!
You can use Socket.io, WebSocket or TCP socket to connect the two servers together and communicate that way. Or you can use a queue system like ZeroMQ or RabbitMQ and communicate that way. Or you can even make an HTTP request from one server to the other one every time you want it to grab new data - or you could even sent that data right in the request.
It would be much easier if you used Redis that supports pub/sub, see:
https://redis.io/topics/pubsub
or CouchDB that supports the changes feed:
http://docs.couchdb.org/en/2.0.0/api/database/changes.html
or RethinkDB that supports changefeeds:
https://rethinkdb.com/docs/changefeeds/javascript/
I don't think Mongo supports anything like that.
I'm developing a web application with Symfony2. I need to create a push notifications sysmte (like Facebook). When an user publish something, I need some of another users receive a notification.
I saw that Node.js it's the easiest manner to do this. But, I did some simple examples and all works fine, but I don't know how can I integrate this node.js application with my Symfony2 application, or really with a PHP application.
Anybody can help me?
Thanks in advance!
Please note that you've not given enough details, so I will respond as a front-end developer and not as a mobile developer
Integrating NodeJS and PHP (in general) is not a good way since you need to launch both servers separatly, create the websocket server in JS while your application is in PHP and finally create a request (GET or POST) from your PHP to you JS server. Well, a big mess, so I'll expose my solution here under.
Quick insight for mobile apps. Well, technically, there's no easy way. You can use the Push "protocol" (http://www.wikiwand.com/en/Push_technology) with NotificationPusher (https://github.com/Ph3nol/NotificationPusher). I didn't used it before so I can't help you with it.
In general.
Most of the time when people thinks of Push, long polling will do the trick. For starters it means that the request is made client-side and the server don't send data & close connection until there's new data.
How do you implement this ?!?
Basically, you change the max_execution_time using ini_set or set_time_limit to a very long time for the current script and launch a loop (like a do..while) with a sleep and the check to your data inside. From your Javascript just make an Ajax call, for example with jquery: $.get. Just remember to remove the timeout and stay in asynchronous mode.
The only drawback of this solution is that you will always have a connection opened to your server which will consume a bit more of battery on a mobile device. If you have multiple types of data to receive do not hesitate to merge the calls and publish a type in your response data, since most of the browsers allows only 2 or 3 simultaneous connections to the same server.
I sounds like your describing WebSockets.
Take a look at Socket.io, its a module for node.js.
Also there is a example at GitHub https://github.com/Automattic/socket.io/tree/master/examples/chat
Interesting files for you should be the index.js and the public/main.js.
You can see the example live at http://socket.io/demos/chat/
I'm trying to build a simple VB.NET/Express 2012 windows application that will be able to receive a POST or JSON object with two parameters:
an XML document
an array or object of parameters
It will get its data from a front-end through JavaScript. That on itself makes a query to the back-end getting the needed info and will then trigger a print task on the local machine where this software is running using a local port to 'talk' to the local application.
I'm just looking for the components to use or some simple examples. Preferably I'd like to run a background TCP listening service that works on it's own (possibly a threaded task inside the application) and fires an event when needed.
Please, remember that it has to be made on the Express version of Visual Studio. I do not have all the extended possibilities the regular Studio has.
All the help is appreciated.
BTW, I've found This thread and this one, but they don't seem to going in the direction I'm wanting to go, as in that they run a continuous loop that seems to disable any and all other input or interaction unless you quit (kill) the application.
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I'm not creating a web application/server - I'm using a PHP solution for that. It's supposed to be a sort-of printserver.
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