I am in the process of prototyping and app (Cordova/phonegap).
I want to know if its possible to have ibeacon information, like (UDID, Major, Minor, Signal Strength) retrieved from my app and then posted from the app to a MySQL database.
Let's say the ibeacon broadcast every 5 seconds then I want all data mentioned above posted to the database.
If it's possible is there a script that can be used as an example?
This is certainly possible and a very common use case. Using a Cordova plugin for beacon detection, you will get callbacks every second with a list of all beacons seen.
How you make a server call in JavaScript is nothing special about beacons. One way with jQuery is:
$.post('/remote-url', {json: jsonString });
The main thing you need to understand is that you probably can't make a call to the server every second. You need to throttle the calls so you only make one every 15-30 seconds or so to keep the requests from piling up.
Related
I am creating a webpage in ReactJS for post feed (with texts, images, videos) just like Reddit with infinite scrolling. I have created a single post component which will be provided with the required data. I am fetching the multiple posts from MySQL with axios. Also, I have implemented redux store in my project.
I have also added post voting. Currently, I am storing all the posts from db in redux store. If user upvotes or downvotes, that change will be in redux store as well as in database, and web-page is re-rendering the element at ease.
Is it feasible to use redux-store for this, as the data will be increased soon, maybe in millions and more ?
I previously used useState hook to store all the data. But with that I had issue of dynamic re-rendering, as I had to set state every time user votes.
If anyone has any efficient way, please help out.
Seems that this question goes far beyond just one topic. Let's break it down to the main pieces:
Client state. You say that you are currently using redux to store posts and update the number of upvotes as it changes. The thing is that this state is not actually a state in your case(or at least most of it). This is a common misconception to treat whatever data that is coming from API a state. In most cases it's not a state, it's a cache. And you need a tool that makes work with cache easier. I would suggest trying something like react-query or swr. This way you will avoid a lot of boilerplate code and hand off server data cache management to a library.
Infinite scrolling. There are a few things to consider here. First, you need to figure out how you are going to detect when to preload more posts. You can do it by using the IntersectionObserver. Or you can use some fance library from NPM that does it for you. Second, if you aim for millions of records, you need to think about virtualization. In a nutshell, it removes elements that are outside of the viewport from the DOM so browsers don't eat up all memory and die after some time of doomscrolling(that would be a nice feature tho). This article would be a good starting point: https://levelup.gitconnected.com/how-to-render-your-lists-faster-with-react-virtualization-5e327588c910.
Data source. You say that you are storing all posts in database but don't mention any API layer. If you are shooting for millions and this is not a project for just practicing your skills, I would suggest having an API between the client app and database. Here are some good questions where you can find out why it is not the best idea to connect to database directly from client: one, two.
I've been trying to resolve this problem for a while now, I even gave it a shot to rewrite the entire program but without success. The application is running on VueJS 2.3.3 and is supposed to be running on Chromium in combination with a Raspberry Pi (irrelevant information, for now).
We're working with several components which are being included in a single file, later on this file will be compiled using either gulp or npm run dev. When the instance of VueJS initializes, a request will be send using Vue Resource's $http option. This'll receive a json response with a size of around 30mb. This'll be saved in the data array, as seen here:
this.$http.get('<url>' + this.token)
.then((response) => {
this.properties = response.properties;
});
This data will later on be used for further actions, another thing that is worth mentioning is that the data is being refreshed every once in a while. Which is where I think the problem occurs, if I'm not refreshing the data every 5 minutes (can be longer too, really depends on the way I'm testing) the program runs fine. It's just that I want to refresh the data every once in a while to retrieve new information. The way of setting a timeout which I'm using is as following:
this.dataTimeout = setTimeout(this.refreshData, 300000);
Each (so called) property has at least 6 base64 images saved in it's JSON, which are later used to present to the user. Besides that, there is a name, address, and some other tiny bits of data. It doesn't sound all that wrong but I'm getting the feeling that each response makes the memory grow so intense that even a desktop is getting trouble running it.
Each 10 seconds a new property will be presented on the user's screen including the images, street, location, etc. I'm not sure if there is a memory leak in my code or if I'm forgetting something. A few questions pop up in my head:
Do I need to reset the response I'm getting from the server back to
null or undefined?
Could there be a leak in one of the plugins I'm using (Just VueResources)?
For how long can a VueJS instance stay alive, is there any recommended time to reload the entire program?
What thinks should I take in consideration in order to achieve this at all?
I've taken out the data renewal and put a demo project online, this can be seen right here. The main problem I'm having is that the browser just runs out of memory and shows us the amazing Aw snap! page from Chrome. I tried taking snapshots from the memory usage but it all seems fine, it just explodes randomly after a while.
Well, I don't know what really does your app, but are your 30Mb of data really useful / essential ? In JSON moreover ?
Maybe you don't need all this data, and you could just adapt the data to your needs. For example, keep your JSON store data, and retrieve your Base64 images by another way.
I don't understand why you store in memory images. Images are just useful for display purpose in my opinion.
So I think 30Mb is really huge. But maybe I'm wrong ?
By the way, I've tested with Firefox Nightly, no problem here. Doesn't seem to crash. Maybe I don't encounter the refresh call ?
I am new to programming and am working on pushing real time data from a PLC to a web page either by deploying HTML 5 on the WAGO or a Modbus driver wrapper. I honestly have tried to research but don't know where to start. it will be a closed private network with little to no influence from the outside web. I am simply looking to display a single piece of live information for proof of concept. basically I'm trying to custom design a Groov program.
You might want to look into using OPC. Kepware & SoftwareToolbox are just 2 of many vendors that offer tools to help you get your data the way you want it.
There is an existing tool to do what you want, but I am under the impression you have to write one from scratch. The existing tool is http://www.softwaretoolbox.com/cogentdatahub/ if you are interested in looking at it for ideas.
I've been able to interface with PLC using python and modbusTCP and an Raspberry pi as the webserver. Python is a quick and easy to learn language. Websockets are the HTML5 component best used for realtime data.
simple connect code (after you install everything):
from pymodbus.client.sync import ModbusTcpClient as ModbusClient
from time import sleep
client = ModbusClient('ip_address_of_modbus_IO')
if(client.connect()):
print(client.read_discrete_inputs(200,1).bits[0])
client.write_coil(0,True)
sleep(100)
client.write_coil(2,True)
found here:
http://simplyautomationized.blogspot.com/2013/09/home-automation-project-2-rpi-light.html
Can create a websocket broadcast server using an example here:
http://simplyautomationized.blogspot.com/2015/09/raspberry-pi-create-websocket-api.html
Fortunately you can not push data to a browser.
The Internet would become an even greater mess if you could.
To solve this, have your webpage contain a timer, written in JavaScript.
Every say 1 sec. it does an AJAX request (e.g. use jQuery implementation) to the server, which then delivers (almost) realtime data.
The webpage then displays that in some DOM element, e.g. an empty DIV.
So it's the browser polling your server.
#BlueDog
The data is "almost" realtime because sampling once a second gives a delay of at least one second. In the ideal case, as soon as data changes, it would be pushed to the browser. Unfortunately the browser has no way of knowing that anything changed, so the best it can do is frequently "ask" for updates (polling).
How much the delay is depends on your poll frequency. If it's once per second one has to add the delays for transmission of the page request and the reply of the server. The transmission time depends on your network (which may be the Internet with all uncertainty involved). If the backbones involved have enough capacity I expect overall delay to be between 1 and 1.5 seconds. With a dedicated network and even more frequent polling, I expect that 0.5 seconds should be possible. These are however estimated averages. If I request a page over the Internet and my provider (again) has a problem, it may be hours before I receive what I want. Also things like virus scanners and OS updates may spoil your game.
So, practically: with a good broadband connection, a stable browser and the right process priorities it should be possible to get below 1 second overall delay (incl. poll time interval) for 95% of the time. Be prepared to reboot the client every few days. Most browsers leak memory and most OS'es do so too.
I'm not after any code in particular but I want to know what is the most efficient way to build a function that will constantly check for updates for things such as messages e.g. Have a chat conversation window and I want live updates such as Facebook.
Currently I have implemented it by putting a while loop in my core code that checks if the view is currently visible run a Task every 5 seconds to get new messages. This works but I don't believe its the most efficient way to do it and I need to consider battery life. *Note I do change visibility when the view goes away e.g. on iOS i do
public override ViewDidDissapper {
Model.SetVisible(false)
}
Has anyone implemented some sort of polling on a cross platform app?
There are many different possible solutions here - which one you prefer depends a lot on your requirements in terms of latency, reliability, efficiency, etc - and it depends on how much you can change server side.
If your server is fixed as a normal http server, then frequent polling may be your best route forwards, although you could choose to modify the 5 seconds occasionally when you think updates aren't likely.
One step up from this is that you could try long polling http requests within your server.
Another step beyond that are using Socket (TCP, UDP or websocket) communications to provide "real time" messaging.
And in parallel to these things, you could also consider using PUSH notifications both within your app and in the background.
Overall, this is a big topic - I'd recommend reading up about PushSharp from #Redth and about SignalR from Microsoft - #gshackles has some blog posts about using this in Xamarin. Also, services like AzureMobileServices, UrbanAirship, Buddy, Parse, etc may help
I'd like to start developing a "simple" game with HTML5 and I'm quite confused by the many resources I found online. I have a solid background in development, but in completely different environments (ironically, I started programming because I wanted to become a game developer, and it's the only thing I've never done in 13 years...).
The confusion derives from the fact that, although I know JavaScript very well and I have some knowledge of HTML5, I can't figure out how to mix what I know with all this new stuff. For example, here's what I was thinking of:
The game would be an implementation of chess. I have some simple "ready made" AI algorithm that I can reuse for single player; the purpose here is to learn HTML5 game development, so this part is not very important at the moment.
I'd like build a website around the game. For this I'd use a "regular" CMS, as I know many of them already and it would be faster to put it up.
Then I'd have the game itself, which, in its "offline" version, has nothing to do with the website, as, as far as I understand, it would live in a page by itself. This is the first question: how to make the Game aware of User's session? The login would be handled by the CMS (it should be much easier this way, as User Managememt is already implemented).
As a further step, I'd like to move the AI to the server. This is the second question: how do I make the game send player's actions to the Server, and how do I get the answer back?
Later on, I'd like to bring a PVP element to the game, i.e. one-against-one multiplayer (like the good old chess). This is the third question: how to send information from a client to another, and keep the conversation going on. For this, people recommended me to have a look at Node.js, but it's one more element that I can't figure out how to "glue" to the rest.
Here's an example of a single action in a PVP session, which already gives me a headache: Player 1 sends his move to the Server (how does the game talk to Node.js?). I'd need to identify the Game Id (where and how should I store it?), and make sure the player hasn't manually modified it, so it won't interfere with someone else's game (how?).
I'm aware that the whole thing, as I wrote it, is very messy, but that's precisely how I feel at the moment. I can't figure out where to start, therefore any suggestion is extremely welcome.
Too many things and probably in the wrong order.
A lot of the issues don't seem to me to be particularly related to HTML5 in the first instance.
Start with the obvious thing - you want a single page (basically a javascript application) that plays chess, so build that. If you can't build that then the rest is substantially irrelevant, if you can build (and I don't doubt that you can) then the rest is about building on that capability.
So we get to your first question - well at the point at which you load the page you will have the session, its a web page, like any other web page, so that's how you get the session. If you're offline then you've persisted that from when you were online by whatever means - presumably local storage.
You want to move the AI to the server? Ok, so make sure that the front end user interaction talks to an "interface" to record the player moves and retrieve the AI moves. Given this separation you can replaces the AI on the client with an ajax (although I'd expect the x to be json!) call to the server with the same parameters.
This gets better, if you want to do player to player you're just talking about routing through the server from one user/player to another user/player - the front end code doesn't have to change, just what the server does at the far end of the ajax call.
But for all this, take a step back and solve the problems one at a time - if you do that you should arrive where you want to go without driving yourself nuts trying to worry about a bucket full of problems that seem scary that you can probably easily solve one at a time and I'd start by getting your game to run, all on its own, in the browser.
About question one: You could maybe give the user a signed cookie. E.g. create a cookie that contains his userid or so and the SHA2 hash of his userid plus a secret, long salt (e.g. 32 bytes salt or so).
About question two: For exchanging stuff and calling remote functions, I'd use the RPC library dnode.
About question three: Use the same thing for calling methods between clients.
Client code (just an example):
DNode.connect(function (remote) {
this.newPeer = function(peer) {
peer.sendChatMessage("Hello!");
};
});
You don't have to use game IDs if you use dnode - just hand functions to the browser that are bound to the game. If you need IDs for some reason, use a UUID module to create long, random ones - they're unguessable.