I am working on a web application where I have to make live updates to the pag. When data is inserted, deleted or updated in the server-side database, then the page will be updated. I have heard about persistent connections. I have also tried AJAX using setTimeInterval(), but the major problem is that when thousands of requests are sent then the browser will start misbehaving. I need something that will make a single request and keep it open/alive and that request will exchange data between the client and the server.
You need PUSH from server, aren't you ? This is the ability for a webapp te receive notifications from the server.
There are several options depending on your server.
For example, I would recommend socket.io for node.js.
Related
I'm looking for technique or skils to fix the ways for new web site.
This site show the read time data which located on server as file or data on memory.
I'll use Node.js for server-side. But I can't fix how to get the data and show that to web site user.
Because this data have to update per 1 second at least.
I think it is similar to the stock price page.
I know there are a lot of ways to access data like AJAX, Angular.js, Socket.io..
Also each has pros and cons.
Which platform or framework is good in this situation?
This ultimately depends on how much control you have over the server side. For data that needs to be refreshed every second, doing the polling on client side would place quite the load on the browser.
For instance, you could do it by simply using one of the many available frameworks to make http requests inside some form of interval. The downsides to this approach include:
the interval needs to be run in the background all the time while the user is on the page
the http request needs to be made for every interval to check if the data has changed
comparison of data also needs to be performed by the browser, which can be quite heavy at 1 sec intervals
If you have some server control, it would be advisable to poll the data source on the server, i.e. using a proxying microservice, and use the server to perform change checking and only send data to clients when it has changed.
You could use Websockets to communicate those changes via a "push" style message instead of making the client browser do the heavy lifting. The flow would go something like:
server starts polling when a new client starts listening on its socket
server makes http requests for each polling interval, runs comparison for each result
when result has changed, server broadcasts a socket message to all connected clients with new data
The main advantage to this is that all the client needs to do is "connect and listen". This even works with data sources you don't control – the server you provide can perform any data manipulation needed before it sends a message to the client, the source just needs to provide data when requested.
EDIT: just published a small library that accomplishes this goal: Mighty Polling ⚡️ Socket Server. Still young, examine for your use if using.
As we know, if running application also manage sessions in main memory then is there any way for server to send responses to all web clients/browsers for new recorded data in a database.
Remember: I have not made any request to server or polling to server for new records update..
Let server make responses without web request..
Objective :
No all web browsers making request or polling to server for every certain interval therefore reducing the performance issue with the application memory..
Am just against of making so many ajax calls from every web client..
Need your ideas from your past, if experienced similar..
read about websockets and socket.io.
basically with socket.io you have a connection open between browser (client) and server and server can send data which the client than receives as an event.
the client doesn't need to send a request to get that data, only open the web socket connection.
you can look at socket.io chat example: http://socket.io/get-started/chat/
WebSocket is the best and easy solution if you don't want to go through the hassle to learn Angular or others.
Both server-side and client-side can build WebSocket, and it acts as a bridge to transmit data back and forth.
I just created an easy solution for this.
Please check my new library wsm - WebSocket Manager, it works for both server-side and client-side.
Websocket Server can be built easily; this library includes several useful features.
I'm creating an app where the server and the clients will run on the same local network. Is it possible to use web sockets, or rather more specifically, socket.io to have one central server and many clients that are running native apps
? The way I understand socket.io to work is that the clients read the web-pages that are served from the server but what happens when your clients become tablet devices running native apps instead of web pages in a browser?
The scenario I'm working with at the minute will have one central server containing a MEAN app and the clients (iPads) will make GET requests to the data available on the server. However, I'd also like there to be real-time functionality so if someone triggers a POST request on their iPad, the server acknowledges it and displays it in the server's client-side. The iPad apps will (ideally) be running native phonegap applications rather than accessing 192.168.1.1:9000 from their browser.
Is this technically possible to connect to the socket server from the native apps or would the devices have to send POST requests to a central server that's constantly listening for new 'messages'? I'm totally new to the whole real-time stuff so I'm just trying to wrap my head around it all.
Apologies if this isn't totally clear, it's a bit hard to describe with just text but I think you get the idea?
Correct me if I am wrong.
You have multiple iPads running native app. They send a POST request to your node JS server which is running in a computer in the same local network. Whenever the server receives a request from app, you want to display that a request has been received in your computer screen.
If my assumptions about the scenario is correct, then it is fairly easy to do. Here are the steps to do it.
Create a small webpage (front end). Load socket IO in the front end page like this -
<script type="text/javascript" src="YOUR_SERVER_IP/socket.io/socket.io.js"></script>
Then connect to server using var socket = io(). This should trigger connection event in your backend.
Handle all POST request from apps normally. Nothing special. Just add a small snippet in between. socket.emit('new_request', request_data). This sends new_request event to front end.
Handle the new_request in your front end using socket.on('new_request', function(request_data) { ... });. That's it. No need to add anything to your native app for realtime update.
The second step would be a little complicated as it is necessary to make socket variable available inside all POST requests. Since you chose node.js, I don't think you need any help with that.
Not totally clear on your project, but I'll try to give you some pointers.
An effective way to send data between native apps and a server is using a REST server. REST is based on HTTP requests and allows you to modify data on the server, which can connect to your database. The data returned is typically either JSON or XML formatted. See here for a brief intro: http://www.infoq.com/articles/rest-introduction
Android/iOS/etc have built in APIs for making HTTP requests. Your native app would send a request to the server, parse the response, and update your native UI accordingly. The same server can be used from a website using jQuery ajax HTTP requests.
Express.js is more suited to serving web pages and includes things like templating. Look into "restify" (see here: mcavage.me/node-restify/) if you just want to have a REST server that handles requests. Both run on top of node.js (nodejs.org).
As far as real-time communication, if you're developing for iOS look into APNS (Apple Push Notification Service). Apple maintains a persistent connection, and by going through their servers you can easily send messages to your app. The equivalent of this on Android is GCM (Google Cloud Messaging).
You can also do sockets directly if that's easier for you. Be careful with maintaining an open socket on a mobile device though, it can be a huge battery drain. Here's a library for connecting ObjC to Socket.IO using websockets, it may be useful for you: https://github.com/pkyeck/socket.IO-objc
Hope that helps!
To answer your question, it is definitely possible. Socket.io would serve as the central server that can essentially emit messages to all of the client. You can also make Socket.io listen for the messages from any of the clients and serve the emitted message to the rest of the clients.
Here's an example of how socket.io can be used. Simply clone, npm install, and run using 'node app.js'
All you have to do is to provide a valid server address when you connect your socket from the iPad clients:
var socket = io.connect( 'http://my.external.nodejs.server' );
Let us know if you need help with actual sending/receiving of socket events.
It is possible to connect to Websockets from your apps.
If you are using PhoneGap then you need a pluging that gives support to websockets in your app (the client) and then use websocket like normal way using Javascript see this.
If your app is native iOS look into this it could help you.
The primary use of the Sockets in your case is to be a bidirectional "pipe" between an app and server. There is no need of server sending the whole web-page to the native app. All what you need is to send some data from server to the client(app) in response to POST (or GET) request and then using this data on client side to update client's UI in real-time. If you are going to use moderate amount of devices (say tens of them), you may have connected all of them to the server permanently keeping individual socket connection open for every individual link server-to-app. Thus you may deliver data and update client's state in real time.
In fact web browsers also employ sockets to communicate to web servers. However as in general case there is no control on amount of concurrent clients in Internet, for the sake of limited networking resources conservation, servers do not keep sockets open for a long time, closing it just after the web-page was sent to client (or timeout has expired). That's how HTTP protocol works on the low level. The server waiting for the HTTP clients (browsers) by listening the 80 port, responding them by sending the whole web page content, then closing the connection and keep waiting for another requests on the same port.
In your case it's basically a good idea to use socket.io as it's a uniform implementation of sockets (ok WebSockets) on both client and server side. The good starting point is here
I'm currently experimenting with WebSockets in a bid to reduce / remove the need for constant AJAX requests in a potentially low bandwidth environment. All devices are WebSocket compliant so there's no issue there, and I'm trying to keep it to native PHP WebSockets, no node.js or other frameworks / libraries (Which so far has been fine).
What I'm looking to do is to decide how to go about notifying connected clients about an update to a database by another Client. The use case in question is a person pressing a button on their device, which then alerts that persons manager(s) to that press. So the two options I have though of are as follows:
1. Looping a Database Query (PHP)
My first thought was to insert a query into the WebSocket server that is effectively saying "Has the alert field changed? If so, notify the manager(s)". Whilst this is the most straightforward and sensible approach (That I can think of), it seems wasteful to have a PHP script designed to reduce strain on the server, that is now running a query every second, however, at least this would ensure that when a Database update is detected, the update is sent.
2. Sending a notification from the Client
Another thought I had, was that when the client updates the Database, they could in fact send a WebSocket notification themself. This has the advantage of reducing any intensive and looped queries, but also means that I'd need to have a WebSocket message being sent every time I want to change any data, such as:
$.post("AttemptDatabaseUpdate.php", {Data}).function(Result) // Don't worry about the semantics of this, it's not actual code
{
if(Result == "Successful")
{
SendWebSocketNotification(OtherData);
}
}
Maybe this is the best option, as it is the most efficient, but I worry that there is a chance the connection may drop between updating the Database, and sending the WebSocket notification, which may create a need for a fallback check in the PHP file, much like the one in the first solution, albeit at a longer interval (Say every 30 seconds).
3. MySQL Trigger?
This is purely a guess, but perhaps another option is to create a MySQL trigger, which can somehow notify the server.php file directly? I've no idea how this would work, and would hazard a guess that this may end up with the same or similar Query requirements as solution #1, but it's just a though...
Thank you in advance for your help :)
EDIT: Solution possibility 4
Another thought has just popped into my head in fact, whereby the PHP file used to update the database could in fact have a WebSocket message built into it. So that when the PHP file updates the database, the WebSocket server is notified via PHP, is this possible?
If you use websockets, you should use notifications from client. That's one of their main use cases.
If you're worried about inconsistencies due to connection dropping or something changing in-between, you could implement a system similar to HTTP ETags, where client would send a hash code that you can respond on server side if there is a conflict in updating.
Update: I guess I understood your initial issue a bit wrong. If I understand your use case correctly: you are sending database updates from a client and after that all connected clients need to be updated. In that case, I think server should send the update messages after DB updates have been done, so I agree with solution 4. I am assuming here that your websocket server is the same server running PHP and doing the DB updates.
However, depending on your use case, client should still send a hash value on the next request identifying its "view of the world", so you would not be doing identical updates multiple times if a connection gets broken.
Update 2: so it was now understood that you indeed use a separate, standalone websocket server. Basically you have two different web servers on the server side and are having an issue on how to communicate between the two. This is a real issue, and I'd recommend only using one server at a time - either take a look at using Apache websocket support (experimental and not really recommended) or migrating your php scripts to the websocket instance.
Neither PHP or Apache was really build with websockets in mind. It is quite easy to set up a standalone websocket server using only PHP, but it might not be so easy then to migrate the rest of the PHP stack to it if the code is relying on Apache/web server on. Apache websocket support also is hardly optimal. For a real websocket solution, unfortunately, best practice would be using a technology that is built for it from the ground up.
The better answer is to send notification through Server side when database is updated by PHP script, so that script have to add options of web sockets to directly send notification to all web socket clients registered.
User send content->Php script process content and save data according to true condition->check database is updated by checking return of mysql_query/other alternative->if true than use web-socket and send notification to all users
now this is more easy/handy/bandwidth saver.
I am creating an internal corporate tool which is entirely client driven and utilizes web services to update, insert, and delete data. While creating the application, I was able to use Chrome Debugger to send any type of request to the server in order to test various scenarios.
I would change objects from the debugger and execute AJAX requests right from the console and there were no issues, the web service would call and execute just fine.
This raised a concern for me in that, a majority of my company employees are developers and i worry that they may "play around" with the code to either change, or invalidate the data going to the database.
Is it possible to secure an AJAX request to the server so that users will not be able to change items in their browser debugger and post those changes to the server?