What are the usual patterns for bidirectional communication between a client and a server in a wlan environment. How is it possible for the server to push data to a mobile client over wlan after a connection has been established.
Lets say I have a webservice running on a server and the moblie cients in the wlan can use this webservice. Now the question is how can the server invoke methods at the client, or directly send data to the client. How is this handled usually?
I would apriciate some links to read about this topic.
Is this a common problem or is it not that easy to solve?
Cheers
HTTP server push (also known as HTTP streaming) is a mechanism for sending data from a web server to a web browser. HTTP server push can be achieved through several mechanisms.
More at http://en.wikipedia.org/wiki/Push_technology#HTTP_server_push
In web development, Comet is a neologism to describe a web application model in which a long-held HTTP request allows a web server to push data to a browser, without the browser explicitly requesting it. Comet is an umbrella term for multiple techniques for achieving this interaction. All these methods rely on features included by default in browsers, such as JavaScript, rather than on non-default plugins.
More at http://en.wikipedia.org/wiki/Comet_(programming)
Also there is a recent IETF draft on
Best Practices for the Use of Long Polling and Streaming in Bidirectional HTTP
https://datatracker.ietf.org/doc/html/draft-loreto-http-bidirectional-01
Related
I have an angular app on a node js server. On another machine, I have an API server. My dilemma is how to communicate with the API server. The first approach is to send all my AJAX calls directly to the API server. The downside of this approach that the client will see how I send the requests to the API, including the secret key I send in the headers. This means I will have to work harder to secure my API. The other approach is to send my requests to my node js server, and then forward them to the API server. The downside of this approach, however, is increased latency, since it will require two serial HTTP requests. I would love to hear from you what you think is the best way to handle this.
Thanks.
First approach, and you "have to work harder to secure your API". I recommend JWT autthorization.
The most popular and reliable solution for this widely followed architecture style (Front End App to Backend API Server) is OAuth.
OAuth is very easy to setup and use with Angular Js.
As far as AJAX calls are concerned, if your application entails this behavior make sure your API is enable with CORS capability.
I am trying to generate lot of requests from my angularjs app to a backend rest server. I am using http service to make the calls. I want to control the concurrency of requests going to server.
I know that browser itself throttles the number of connetions per server.
Now my questions are:
How can I control the number of connections chrome opens to a server? How to do it using angularjs?
How does the angularjs http service works? Does it opens and close the http connection every time I make a http call? If yes then how can I create persistent connections in angularjs?
XMLHttpRequest is used under the hood. Since it uses HTTP, most of the answers to your questions are dependent on the headers you use and the server you are communicating with. For instance, whether or not connections persist depend on whether or not Keep-Alive is specified and the server supports it.
As for the number of connections, this is generally limited by the browser on a per domain basis. You won't be able to make use of more than the browser can allow, but you can probably write your own code to throttle it down if you so desire.
This question has good information about connection limits for the various browsers.
I am creating a web application using GAE/GWT. Front end GUI is a web client and the server is a RESTFUL server both running in GAE in different domains.
I am using json with padding to communicate with the server but discovered I won't be able to send a PUT/POST/DELETE request.
My application will be used to mainly used to query data (query: 85% of cases, modify data: 15%). All requests will be authenticated.
I am considering the following options.
1) For querying use JsonpRequestBuilder, for modifying create a proxy in the web client server side and hit the REST service through this proxy. Use GWT RPC to communicate to this proxy.
2) Make every request as a GET request in my REST service (including those that modify data) and use jsonp directly from web client.
I would prefer option 1) but option 2) seems less work to do.
Should 1) be my preferred option ?
Are there any problems with 2) given all my requests will be authenticated. ?
Is there any other easy approach to solve this problem ?
Regards,
Sathya
The simplest solution is to use CORS which allows you to send requests two different origins. But it is not so widely spread (check caniuse), so if you have to support IE8-9, it will not be enough for you.
In your case I would try to implement dual solution (e.g. CORS + server proxy). If browser supports CORS - send the request directly to the target server, if it doesn't - send request via proxy.
Sorry to ask but what is the advantage to have your client running on a different domain ? From what I understand your client's server will do nothing ...
If you are not the "owner" of the REST backend, maybe this backend should developp an authorization system for third party applications, like oauth2.
Then your application can talk backend to backend with a secured connection. You can use scribe to do that on your backend.
Is is must to have the client to be browser for a web server? Is this a good architecture for mobile clients to have some non browser client and get data from webservers?
I am thinking of implementing a basic browser at mobile client. Login using web methos and rest of the communication (monitoring info at every 10sec) be done using web sockets. Will this work?
Can I implement web sockets without JS?
Thanks
You can implement WebSockets outside the browser, and without any JavaScript involved. You could have i.e. a Android native Java application that talks to a server over WebSockets.
WebSockets is a protocol. The WebSockets API defined for JavaScript running in the browser is something different.
You can authenticate a WebSockets connection during the WebSockets handshake using any method available with HTTP (i.e. basic auth, digest, cram-md5, client cert.-based (TLS), and so on), since the WebSockets handshake is still like any other HTTP conversation. It is only after the handshake is completed that WS is different from HTTP.
Note, that what you likely want on the server side is not a plain old Web server, but a WebSockets server/framework.
Whether using WS to connect mobile clients is "a good architecture" is a bit vague. I would say: if you decide to have your mobile client talk to a server, and that server is under your control, and you want to leverage WS advantages like near real-time/bidirectional, then it might be good. Better than cooking your own low-level protocol.
I would like to build a mobile application with the following requirements:
The mobile client applications should request and recieve data from a database on a server.
In the future I will probably want to build a web application for the same database.
For communication between the clients and the server I would like to use Google Protocol Buffers.
So I have the following questions:
How does one set up a server to take request and respond with anything other than html. I think that using RPC sounds nice, but I have no clue how to set it up on a server.
I need to find a good web hosting service which will allow me to set up a database and a server that can serve both Google Protocol Buffers and regular web pages with data.
Before I get to making the web app, is there any more lightweight solution that might be better just for communicating with the clients (maybe even a home made tiny server), and how hard would it be to do it with a full scale web server from the start?
Please point me in the right direction so I know what to read up on.
I'm not necessarily looking for specific names of web hosting services but rather an idea what kind of services are available that might meet my needs. I've worked a little bit with django, Spring and Java EE so if there's any solution involving those that would be great, however I'm not afraid of learning something new.
Thanks in advance
Simon
if you still mean http, that is pretty trivial - you simply set an appropriate content-type, and write your data to the response stream. The exact how depends on your web framework and tools, but this is no different to (say) serving generated images on the fly. HTTP requests function fine for messaging scenarios - as simple as making an http request (typically POST) with a protobuf (etc) body, and processing the response in the same way.
can't comment
a web app can be lightweight; certainly more-so than having to configure a non-http service/daemon. The "lightweight" option would be raw sockets, but that is harder to deploy, and you'll have to be more picky choosing a host. Unless you absolutely need this level of terseness (i.e. dropping the http headers and writing your own transport to get close to the wire), just stick with http - it'll be a lot easier to get going and maintain
For info, I have a blog post on doing this with ASP.NET MVC; this isn't intended to mean "do this" (heck, use whatever tools help you) - simply, it is meant to show the kind of thing necessary.