sorry if this question sounds kinda weird, but I haven't managed to get a satisfying answer yet.
The thing is, I am making( or willing to make ) a web-browser based game where people have their own company, trade, build etc.. And the game will also include bots. Because there will be quite a lot happening, it would be good for the bots to run at all times and react to various situations.
But.. I don't know how to make it happen server-side. Is there a way to make a script run on a server (like VPS)? Or is there a way to make some kind of application that would run on the server and communicate with the database and send answers?
Thank you :)
Of course there is a way to do this server-side - you "just" have to create a server, using any language/framework/platform that enables you to create a proper server application (this could be C++, Java, you could even stay in the JavaScript realm by using Node.js).
You would have to provide some kind of communication channel between web clients and your server. For that, you could use either Websockets (TCP) or WebRTC (UDP), simple AJAX could be an option too, but I wouldn't recommend it for persistent communication channel.
I am using Flask and I want to show the user how many visits that he has on his website in realtime.
Currently, I think a way is to, create an infinite loop which has some delay after every iteration and which makes an ajax request getting the current number of visits.
I have also heard about node.js however I think that running another process might make the computer that its running on slower (i'm assuming) ?
How can I achieve the realtime updates on my site? Is there a way to do this with Flask?
Thank you in advance!
Well, there are many possibilites:
1) Polling - this is exactly what you've described. Infinite loop which makes an AJAX request every now and then. Easy to implement, can be easily done with Flask however quite inefficient - eats lots of resources and scales horribly - making it a really bad choice (avoid it at all costs). You will either kill your machine with it or the notification period (polling interval) will have to be so big that it will be a horrible user experience.
2) Long polling - a technique where a client makes an AJAX request but the server responds to that request only when a notification is available. After receiving the notification the client immediately makes a new request. You will require a custom web server for this - I doubt it can be done with Flask. A lot better then polling (many real websites use it) but could've been more efficient. That's why we have now:
3) WebSockets - truely bidirectional communication. Each client maintains an open TCP connection with the server and can react to incoming data. But again: requires a custom server plus only the most modern browsers support it.
4) Other stuff like Flash or Silverlight or other HTTP tricks (chunked encoding): pretty much the same as no 3). Though more difficult to maintain.
So as you can see if you want something more elegant (and efficient) than polling it requires some serious preparation.
As for processes: you should not worry about that. It's not about how many processes you use but how heavy they are. 1 badly written process can easily kill your machine while 100 well written will work smoothly. So make sure it is written in such a way that it won't freeze your machine (and I assure you that it can be done up to some point defined by number of simultaneous users).
As for language: it doesn't matter whether this is Node.js or any other language (like Python). Pick the one you are feeling better with. However I am aware that there's a strong tendency to use Node.js for such projects and thus there might be more proper libraries out there in the internets. Or maybe not. Python has for example Twisted and/or Tornado specially for that (and probably much much more).
Websocket is an event-driven protocol, which means you can actually use it for truly real-time communication.
Kenneth Reitz wrote an extension named Flask-Sockets that is excellent for websockets:
Article: introducing-flask-sockets
Github: flask-sockets
In my opinion, the best option for achieving real time data streaming to a frontend UI is to use a messaging service like pubnub. They have libraries for any language you are going to want to be using. Basically, your user interfaces subscribe to a data channel. Things which create data then publish to that channel, and all subscribers receive the publish very quickly. It is also extremely simple to implement.
You can use PubNub and specifically PubNub presence meant especially for online presence detection. It provides key features like
Track online and offline status of users and devices in realtime
Occupancy to monitor user and machine presence in realtime
Join/Leave Notification for immediate updates of all client connections
Global Scale with synchronized servers across the PubNub Data Stream Network
PubNub Presence Tutorial provides code that can be downloaded to get presence up and running in a few minutes. Five Ways You Can Use PubNub Presence shows you the different ways you can use PubNub presence.
You can get started by signing up for PubNub and getting your API keys.
I hope this is okay to ask here as its more a request for advice than a technical problem.
I have been developing a game using html5+js and my goal was to make it multiplayer. It's a dungeon crawling game and my intent is to have a main village where all players online and in the village can see each other going about and talk and form parties but when a player enters a dungeon its a seperate instance for them and their party. Party size maxium of 4.
My intention was to use websockets and write a server in c#. The problem is I just found out that IE does not support websockets and is still holding around 25% of the browser market share.
my options seem to be to use websockets anyway and cut out the IE crowd or maybe drop multiplayer support. Someone else suggested that I just write world data to a database and have players read from it every frame and update that way.. it sounds horriable.
I found this socket.io thing that seems like it can use websockets OR do the same deal in other ways - but how does this effect me writing a server? If I use the c# implementation of websockets and socket.io will IE users be able to talk to my server?
Or there may be other ways of doing client->server communication that I don't even know about.
To be completely honest i'm tempted to drop the multiplayer idea! But before I do I look to you guys for advice and experienced suggestions on how I could handle this. Thanks for your time and I hope this kind of question is okay here :)
Do not drop the multiplayer idea! It's way cooler with multiplayer. :)
Socket.io is a Server-Side JavaScript library. This means that you need Node JS server for it. IE users will be able to talk with Socket.io server, because it uses other protocols if WebSockets are not available. For example: FlashSocket or XHR long-polling. The last technique is available in every browser that supports XHR, but it is inefficient.
The greatest advantage of socket.io is the fallback. You can set it to start with any protocol (like WebSockets) and if the client does not support it, then it tries the others. It is really great, since you can use WebSockets (which will slowly but surely dominate web apps) and still work with browsers which do not support it, like IE or Opera or Safari. I don't know whether there is any other library with this advantage.
I don't know any library for real-time connections for C# (I'm not a C# developer), but it is unlikely that there are none (look at this question). Also note that real-time connections require a bit different server architecture then normal HTTP requests, so probably you will need additional server for handling them.
Also I think that neither nginx nor Apache handle WebSockets (without some hard core tricks) at the moment (but Node JS does!). I'm not sure though.
There is no reason to lock yourself in platform-wise for something as simple as transport. Support for these things change over time, and you will want to decouple yourself from them as much as possible. You are, after all, making a game, not a network tech demo.
Have a look at Orbited/Orbited2 TCPSocket. You can write your server as standard TCP in whatever manner you like. This also makes life easier if you decide to make a native client.
I've been developing in the .NET stack for the past five years and with the latest release of MVC3 and .NET 4.0 I feel like the direction I thought things were headed in were further confirmed.
With the innovative steps the client community has in such a short period of time, it seems like the best in class apps have a UX controlled by a majority of client events. For example, facebook.com, stackoverflow.com, google, www.ponched.com :), etc. When I say client events I am not talking about a server side control wrapped in an UpdatePanel to mask the postback. I am talking about doing all events and screen transitions on the client and use full postbacks only when really necessary. That's not to say things like .NET aren't essential tools to help control security, initial page load, routing, middle tier, etc.
I understand when working on a simple application or under aggressive time constraints using the controls and functionality provided by default by .NET (or other web dev frameworks) isn't practical if the project calls for it but it seems like the developers that can set themselves apart are the ones you can get into the trenches of Javascript/jQuery and provide seamless applications that have limited involvement from the (web) server. As developers we may not think our users are getting more sophisticated because of the big name web applications they are using on the reg but I am inclined to think they are.
I am curious if anyone shares this view or if they have another take on this? Some post lunch thoughts I figured I'd fire out there and see what I got back.
I share this view. We've ironically moving away from thin client and back to thick client, although this time around everything on the client is distributed on-demand via the server so obviously the maintenance overhead is nothing like it used to be.
Rich client-side functionality not only gives you fluid, responsive, interactive apps, but has the significant advantage for large scale sites and applications of being able to palm off a large chunk of processing resources to client browsers rather than having to process everything at their end. Where tens or hundreds of millions of users are involved, this amounts to a very large saving.
I could say more on the matter but time is short. I'm sure there will be other views (assuming the question isn't closed for being subjective).
The point about the developers who set themselves apart is definitely on target. Developers who understand the underlying technologies and can produce customized solutions for their clients are indeed set apart from developers who can drag and drop framework tools and wire up something that works well enough.
Focusing on web development in this discussion, it's vitally important that developers understand the key technologies in play. I can't count how many times I've encountered "web developers" (primarily in the Microsoft stack, since that's where I primarily work) who patently refuse to learn JavaScript/HTML/CSS simply because they feel that the tooling available to them in Visual Studio does the job just fine.
In many cases it does, but not in all cases. And being able to address the cases where it doesn't is what puts a developer above the rest. Something as simple as exposing a small RESTful JSON API and using AJAX calls to fetch just the necessary data instead of POSTing an entire page and re-processing the entire response means a lot to the overall user experience. Both get the job done, but one is considerably more impressive to the users than the other.
Frameworks are great when what you want to do is fully encapsulated in the feature set of the framework. But when you need to grow beyond the framework, it ends up being limiting. That's where a deeper understanding of the underlying technologies would allow a developer to grow outside of the framework tooling and produce a complete solution to the client.
You are right in saying that modern web development involves technologies like jQuery (or similar libraries) and JavaScript in general.
Full page reloads are old fashion and Ajax approach is the way to go, just don't think that the web server is less used or involved than before, it still responds to the ajax calls simply it does it asynchronously :)
MVC does not support any post back actually, because there are no web forms and there is not the same model of page life cycle.
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I have an application whose primary function works in real time, through websockets or long polling.
However, most of the site is written in a RESTful fashion, which is nice for application s and other clients in the future. However, I'm thinking about transitioning to a websocket API for all site functions, away from REST. That would make it easier for me to integrate real time features into all parts of the site. Would this make it more difficult to build applications or mobile clients?
I found that some people are already doing stuff like this: SocketStream
Not to say that the other answers here don't have merit, they make some good points. But I'm going to go against the general consensus and agree with you that moving to websockets for more than just realtime features is very appealing.
I am seriously considering moving my app from a RESTful architecture to more of an RPC style via websockets. This is not a "toy app", and I'm not talking about only realtime features, so I do have reservations. But I see many benefits in going this route and feel it could turn out to be an exceptional solution.
My plan is to use DNode, SocketIO, and Backbone. With these tools, my Backbone models and collections can be passed around from/to client and server by simply calling a functions RPC-style. No more managing REST endpoints, serializing/deserializing objects, and so forth. I haven't worked with socketstream yet, but it looks worth checking out.
I still have a long way to go before I can definitively say this is a good solution, and I'm sure it isn't the best solution for every application, but I'm convinced that this combination would be exceptionally powerful. I admit that there are some drawbacks, such as losing the ability to cache resources. But I have a feeling the advantages will outweigh them.
I'd be interested in following your progress exploring this type of solution. If you have any github experiments, please point me at them. I don't have any yet, but hope to soon.
Below is a list of to-read-later links that I've been collecting. I can't vouch that they are all worthwhile, as I've only skimmed many of them. But hopefully some will help.
Great tutorial on using Socket.IO with Express. It exposes express sessions to socket.io and discusses how to have different rooms for each authenticated user.
http://www.danielbaulig.de/socket-ioexpress/
Tutorial on node.js/socket.io/backbone.js/express/connect/jade/redis with authentication, Joyent hosting, etc:
http://fzysqr.com/2011/02/28/nodechat-js-using-node-js-backbone-js-socket-io-and-redis-to-make-a-real-time-chat-app/
http://fzysqr.com/2011/03/27/nodechat-js-continued-authentication-profiles-ponies-and-a-meaner-socket-io/
Tutorial on using Pusher with Backbone.js (using Rails):
http://blog.pusher.com/2011/6/21/backbone-js-now-realtime-with-pusher
Build application with backbone.js on the client and node.js with express, socket.io, dnode on the server.
http://andyet.net/blog/2011/feb/15/re-using-backbonejs-models-on-the-server-with-node/
http://addyosmani.com/blog/building-spas-jquerys-best-friends/
http://fzysqr.com/2011/02/28/nodechat-js-using-node-js-backbone-js-socket-io-and-redis-to-make-a-real-time-chat-app/
http://fzysqr.com/2011/03/27/nodechat-js-continued-authentication-profiles-ponies-and-a-meaner-socket-io/
Using Backbone with DNode:
http://quickleft.com/blog/backbone-without-ajax-part-ii
http://quickleft.com/blog/backbone-without-ajax-part-1
http://sorensen.posterous.com/introducing-backbone-redis
https://github.com/cowboyrushforth/minespotter
http://amir.unoc.net/how-to-share-backbonejs-models-with-nodejs
http://hackerne.ws/item?id=2222935
http://substack.net/posts/24ab8c
HTTP REST and WebSockets are very different. HTTP is stateless, so the web server doesn't need to know anything, and you get caching in the web browser and in proxies. If you use WebSockets, your server is becoming stateful and you need to have a connection to the client on the server.
Request-Reply communication vs Push
Use WebSockets only if you need to PUSH data from the server to the client, that communication pattern is not included in HTTP (only by workarounds). PUSH is helpful if events created by other clients needs to be available to other connected clients e.g. in games where users should act on other clients behaviour. Or if your website is monitoring something, where the server pushes data to the client all the time e.g. stock markets (live).
If you don't need to PUSH data from the server, it's usually easier to use a stateless HTTP REST server. HTTP uses a simple Request-Reply communication pattern.
I'm thinking about transitioning to a WebSocket api for all site functions
No. You should not do it. There is no harm if you support both models. Use REST for one way communication/simple requests & WebSocket for two way communication especially when server want to send real time notification.
WebSocket is a more efficient protocol than RESTful HTTP but still RESTful HTTP scores over WebSocket in below areas.
Create/Update/Delete resources have been defined well for HTTP. You have to implement these operations at low level for WebSockets.
WebSocket connections scale vertically on a single server where as HTTP connections scale horizontally. There are some proprietary non standards-based solutions for WebSocket horizontal scaling .
HTTP comes with a lot of good features such as caching, routing, multiplexing, gzipping etc. These have to built on top of Websocket if you chose Websocket.
Search engine optimizations works well for HTTP URLs.
All Proxy, DNS, firewalls are not yet fully aware of WebSocket traffic. They allow port 80 but might restrict traffic by snooping on it first.
Security with WebSocket is all-or-nothing approach.
Have a look at this article for more details.
The only problem I can using TCP (WebSockets) as your main web content delivery strategy is that there is very little reading material out there about how to design your website architecture and infrastructure using TCP.
So you can't learn from other people's mistakes and development is going to be slower. It's also not a "tried and tested" strategy.
Of course your also going to lose all the advantages of HTTP (Being stateless, and caching are the bigger advantages).
Remember that HTTP is an abstraction for TCP designed for serving web content.
And let's not forget that SEO and search engines don't do websockets. So you can forget about SEO.
Personally I would recommend against this as there's too much risk.
Don't use WS for serving websites, use it for serving web applications
However if you have a toy or a personal websites by all means go for it. Try it, be cutting-edge. For a business or company you cannot justify the risk of doing this.
I learned a little lesson (the hard way). I made a number crunching application that runs on Ubuntu AWS EC2 cloud services (uses powerful GPUs), and I wanted to make a front-end for it just to watch its progress in realtime. Due to the fact that it needed realtime data, it was obvious that I needed websockets to push the updates.
It started with a proof of concept, and worked great. But then when we wanted to make it available to the public, we had to add user session, so we needed login features. And no matter how you look at it, the websocket has to know which user it deals with, so we took the shortcut of using the websockets to authenticate the users. It seemed obvious, and it was convenient.
We actually had to spend quiet some time to make the connections reliable. We started out with some cheap websocket tutorials, but discovered that our implementation was not able to automatically reconnect when the connection was broken. That all improved when we switched to socket-io. Socket-io is a must !
Having said all that, to be honest, I think we missed out on some great socket-io features. Socket-io has a lot more to offer, and I am sure, if you take it in account in your initial design, you can get more out of it. In contrast, we just replaced the old websockets with the websocket functionality of socket-io, and that was it. (no rooms, no channels, ...) A redesign could have made everything more powerful. But we didn't have time for that. That's something to remember for our next project.
Next we started to store more and more data (user history, invoices, transactions, ...). We stored all of it in an AWS dynamodb database, and AGAIN, we used socket-io to communicate the CRUD operations from the front-end to the backend. I think we took a wrong turn there. It was a mistake.
Because shortly after we found out that Amazon's cloud services (AWS) offer some great load-balancing/scaling tools for RESTful applications.
We have the impression now that we need to write a lot of code to perform the handshakes of the CRUD operations.
Recently we implemented Paypal integration. We managed to get it to work. But again, all tutorials are doing it with RESTful APIs. We had to rewrite/rethink their examples to implement them with websockets. We got it to work fairly fast though. But it does feel like we are going against the flow.
Having said all that, we are going live next week. We got there in time, everything works. And it's fast, but will it scale ?
I would consider using both. Each technology has their merit and there is no one-size fits all solution.
The separation of work goes this way:
WebSockets would be the primary method of an application to communicate with the server where a session is required. This eliminates many hacks that are needed for the older browsers (the problem is support for the older browsers which will eliminate this)
RESTful API is used for GET calls that are not session oriented (i.e. not authentication needed) that benefit from browser caching. A good example of this would be reference data for drop downs used by a web application. However. can change a bit more often than...
HTML and Javascript. These comprise the UI of the webapp. These would generally benefit being placed on a CDN.
Web Services using WSDL are still the best way of enterprise level and cross-enterprise communication as it provides a well defined standard for message and data passing. Primarily you'd offload this to a Datapower device to proxy to your web service handler.
All of this happen on the HTTP protocol which gives use secure sockets via SSL already.
For the mobile application though, websockets cannot reconnect back to a disconnected session (How to reconnect to websocket after close connection) and managing that isn't trivial. So for mobile apps, I would still recommend REST API and polling.
Another thing to watch out for when using WebSockets vs REST is scalability. WebSocket sessions are still managed by the server. RESTful API when done properly are stateless (which mean there is no server state that needs to be managed), thus scalability can grow horizontally (which is cheaper) than vertically.
Do I want updates from the server?
Yes: Socket.io
No: REST
The downsides to Socket.io are:
Scalability: WebSockets require open connections and a much different Ops setup to web scale.
Learnin: I don't have unlimited time for my learnin. Things have to get done!
I'll still use Socket.io in my project, but not for basic web forms that REST will do nicely.
WebSockets (or long polling) based transports mostly serve for (near) real-time communication between the server and client. Although there are numerous scenarios where these kinds of transports are required, such as chat or some kind of real-time feeds or other stuff, not all parts of some web application need to be necessarily connected bidirectionally with the server.
REST is resource based architecture which is well understood and offers it's own benefits over other architectures. WebSockets incline more to streams/feeds of data in real-time which would require you to create some kind of server based logic in order to prioritize or differentiate between resources and feeds (in case you don't want to use REST).
I assume that eventually there would be more WebSockets centric frameworks like socketstream in the future when this transport would be more widespread and better understood/documented in the form of data type/form agnostic delivery. However, I think, this doesn't mean that it would/should replace the REST just because it offers functionality which isn't necessarily required in numerous use cases and scenarios.
I'd like to point out this blog post that is up to me, the best answer to this question.
In short, YES
The post contains all the best practices for such kind of API.
That's not a good idea. The standard isn't even finalized yet, support varies across browsers, etc. If you want to do this now you'll end up needing to fallback to flash or long polling, etc. In the future it probably still won't make a lot of sense, since the server has to support leaving connections open to every single user. Most web servers are designed instead to excel at quickly responding to requests and closing them as quickly as possibly. Heck even your operating system would have to be tuned to deal with a high number of simultaneous connections (each connection using up more ephemeral ports and memory). Stick to using REST for as much of the site as you can.