3

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?

leaksterrr
  • 3,800
  • 7
  • 34
  • 65
  • Have you already tried it? http://maniacdev.com/2013/01/an-ios-objective-c-socket-io-client-library-for-easy-real-time-web-communication If I correctly understood you question this may help... – matteospampani Jun 09 '14 at 01:18

6 Answers6

1

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.

  1. 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.

  2. 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.

  3. 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.

0

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!

Greg T
  • 3,278
  • 3
  • 37
  • 39
  • All you've done is tell me what each technology is responsible for in the development cycle, which if I'm already working them, I know exactly what they do... – leaksterrr Jun 04 '14 at 09:38
0

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'

Sean
  • 779
  • 6
  • 18
0

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.

Ingmars
  • 998
  • 5
  • 10
0

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.

Community
  • 1
  • 1
Qusai Jouda
  • 1,048
  • 8
  • 12
0

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

esboych
  • 985
  • 2
  • 10
  • 16