when i use comet iframe i just send script tags from backend php file to front end and javascript is displaying it.
can someone explain briefly where a comet server comes up in the picture and how the communication will be between frontend (javascript), backend (php) and the comet server.
cause i read that if you are going to let a lot of users use your comet application it's better to have a comet server. but i dont quite understand the coupling between these parts.
use this link:
http://www.zeitoun.net/articles/comet_and_php/start
That is the best tutorial i could found, and takes 1 min to try;
in short:
( image from that tutorial )
index, can be html or php, creates a request, which php doesnt answer until there is data to send back, with chat, when someone sends you a message.
If you have many users chatting, i recommend using a java chat app
otherwise your server will load up with running php engines ( each unanswered request keeps a php engine alive, which is server capacity ).
http://streamhub.blogspot.com/2009/07/tutorial-building-comet-chat.html
this should help you out with that, but you do need java hosting :)
have fun
edit:
just read the other server part; sending requests to your own server can get messed because the timeout function may not work well, so the server crashes, an independant server timeouts the connection after a certain amount of time, no matter what.
I have a very simple example here that can get you started with comet. It covers compiling Nginx with the NHPM module and includes code for simple publisher/subscriber roles in jQuery, PHP, and Bash.
http://blog.jamieisaacs.com/2010/08/27/comet-with-nginx-and-jquery/
A working example (simple chat) can be found here:
http://cheetah.jamieisaacs.com/
Related
I've written a game server in python which communicates to multiple pygame clients via sockets. Since it's a turn-based card game there isnt that much data flowing and it's in JSON format. Because I don't want people having to download the client I've started working on a 3D UI with three.js and it's not looking bad.
However I am currently stuck with the communication between the backend (my python game server) and the frontend (The webpage / client I am building with html, javascript and three.js). I feel like my question is already pretty specific and don't get any helpful results when looking online.
How can the webpage (client) and the python server communicate? What changes do I need to make on the python server side? And what do I need to know to implement this on the client side in javascript?
Because your client is running in a web browser, your main limitation is what the browser supports. Javascript in browsers is severely limited so that a website can't trick computers that visit the website into doing bad stuff.
So the first step is to find out "How can my Javascript web page communicate with a backend at all?" and then once you have chosen something, write the backend after that.
You have two options: HTTP requests (AJAX) or websockets.
An HTTP request is basically the same way the browser downloads the page to begin with, and the pictures on the page. The browser says to the server "hey, give me the address http://127.0.0.1:8000/play_card?card_number=3 and the server says back "the page says OK". Little does the browser know, that your server made you play card number 3 and now it's the next player's turn.
This is one-way - the client can ask for stuff, the server can't just send it. So the client has to keep asking over and over, whether anything has happened. The client might ask for address http://127.0.0.1:8000/game_status?player=5 and maybe the server says {} if nothing has changed. (Or maybe it says the entire game status and then you don't need the player number. Depends on the game.)
The other option is websockets. The browser sends a special request saying "hey please make this connection into a websocket" and the server sends a special response saying "okay, this connection is now a websocket", and then the connection stays open for as long as the client wants, and the client and server can send data at any time. It's not just a normal socket, though, because there are extra security measures to prevent the webpage from doing naughty stuff. And the connection always starts with an HTTP request and response.
In either case, note that http://127.0.0.1:8000 has to be the same website that the web page came from - websites can't just send requests to other websites (that would be naughty), so your server also has to serve the game page itself. (not difficult)
You can implement HTTP and/or websockets yourself by listening on a socket on port 8000 (or any other port), but you'll have to learn the HTTP protocol and get it right or else it won't work. It's actually not too difficult but it is work that you have to do. Or you can use a library someone else wrote, like http.server or websockets.
so on client side running in the browser I have a javascript code that has a variable (namely a url that is 1500 characters long), and which I need to insert it into a online database that lives on the webserver where I have hosted my website. I have these two technologies on my website, mysql DB and PHP.
Please kindly would someone recommend the best way to do this?
showing examples, specifically, how to send this data over to the remote server and how to process return data it may send back to me??
what i was thinking if there's a way to send over this variable string that is 1500 characters long, over to a PHP file living on my website which this PHP file will be able to insert the data into the DB, and then some time afterwards my same script running on the client browser will check and pull data from the remote DB back to itself...... I've tried to follow along some example searches googling but none of them are making sense to me, sorry I am visual learner , and would greatly appreciate any help you may provide me with this task .....
The solution already discussed here is the proper one. You need an API (also called a service).
I don't know who downvoted it but its the right one.
And you need it for several reasons.
Performance issues. Your solution "writting to a file" will be slow. And even "writting to a file" will require a service on top.
Security reasons. To allow in any other kind of way for a user to write in your server directly (FTP or other methods) is a big security risk and your server might end up being attacked.
Scalability and mantainance.
I would recommend reading more at
https://code.tutsplus.com/tutorials/a-beginners-guide-to-http-and-rest--net-16340
And if you are a bigginer an want to start something fast loopback is an amazing option, but you need NodeJS in your server.
In broad terms what you need to do is set up a API on the PHP side of things. Basically you want a structure where your javascript can send the request, and then, using promises, wait till it gets a response to get the data. That way your PHP server can take however long it needs to put the data in the database and process it properly.
Here's a tutorial on how to make a restful api in php
i have developing a website that user can chat with other user if they are online . if one user send a message will notify that receiver on their screen , these checking process are happen in background process , i have an option of using
setinterval method and javascript self execution method
but i am looking much faster background process methods which will check every seconds if message or notification arrived .
could any one give suggestion for this.
You can use HTML5 websockets.
WebSockets is an advanced technology that makes it possible to open an interactive communication session between the user's browser and a server. With this API(JS functions), you can send messages to a server and receive event-driven responses without having to poll the server for a reply.
below is good link to start
http://www.sanwebe.com/2013/05/chat-using-websocket-php-socket
I think the best match for your needs will be http://elephant.io
Elephant.io provides a socket.io client fully written in PHP that should be usable everywhere in your project.
Take a look at the Thruway Project. It's a PHP websocket implementation using the WAMP protocol, which gives you Publish and Subscribe abilities (you can use that for your chat application) as well as RPC.
A good place to start would to take a look at this chat demo (source code) and then use Thruway as the WAMP router.
I'm one of the developers of the thruway project, so if you run into any issues or have any questions, feel free to ask.
If a Client is requesting something from the server, I want to send some extra information to the client along with the requested page. That web page is being processed by JavaScript on loading. Sometimes I require updating the DOM using the data which I have received from server. Can I get some pointers on how I can implement solution?
According to my understanding of your question. To communicate javascript to server and server to javascript you can use signalR. For more information please see.
http://www.asp.net/signalr/overview/getting-started/tutorial-getting-started-with-signalr
Generally this method is used for chat application. I think for your problem this is one the solution.
please correct me if I am wrong.
I thing that websocket is your best solution, of course this only will work with modern browser (not IE, just IE 10), but if you are using nodejs in server side, you can use socket.io, http://socket.io/ they say that work even in IE 5.5+
So I was learning JavaScript/jQuery and building a website as I go along. Now I need to have a database, and my friend recomended learning Ruby and using it to handle data. From this question: JavaScript Execute Ruby Script It shows how I could execute the Ruby script, but I was wondering if it is possible to send data to that script so it can push it to a MySQL database?
Basically the user would submit a string, and all the stuff is dynamically generated by JS, so I want to send that string to the SQL db as soon as the user submits it. If anyone can point me in the right direction in terms of readings. I don't have much knowledge/experience in Ruby so anything that redirects me to something useful for this particular task would be great. Thanks!
The question you referred to is probably not what you want. That will only work if the server is on the same machine as your browser and if that machine runs Windows.
For a website, that everybody can visit you need to have a server that runs some software - in your case written in ruby - and that is sent requests by the browser - in your case through your JavaScript program.
To do that you need to send an XMLHttpRequest. For jQuery you can read about this in the docs or in a tutorial. This way you get your browser to talk to the server.
For the server to listen and respond you should use some framework like Ruby on Rails or (not Ruby but Python) Django.