Last semester we had to develop the game Ludo in JavaScript and HTML/CSS. That was pretty easy. Now we have to develop a backend with GWT (Java) to create a multiplayer game. Sadly, we haven’t got much information on how to develop with GWT and the exercise is quite difficult at the beginning.
At the moment I am trying to create a kind of lobby where different players can join.
My idea was to use some input fields, where the player could enter his name and join the lobby. But I don’t know how to give the other clients the information that a new player has joined.
I created an asynchronous interfaces (RPC) where a player could submit his name to the server (Like this example). This works ok. But how should I share this information? Our docent said we should use JSON to share information’s, but I don’t know how this should help in this situation.
Is there a way to send information’s to the clients? I read a lot and just find to use additional libraries as gwt-comet.
I have really now clue how I could go on. I’m thankful for every help and information!
Greetz
You have two options: push and pull.
"Pull" option:
Other players get required information when they join the lobby and/or do something else. You can also schedule to pull this information periodically (like once every 10 minutes). You can use the same RPC mechanism to get data from server to a client. "Pull" means that a client initiates the request and server responds with the information.
"Push" option:
When a new player joins, the server pushes this new data to all other players. The best solution depends on your game implementation. Comet is a good option, as Jean-Michel mentioned, but it's more complicated and "expensive" from resources point of view. You should use this option if you need real-time status updates for your game.
I would suggest Errai and ErraiBus in particular. From Java perspective you are only sending some events via event bus (observer GoF pattern) and all the magic with Ajax Push is happening behind the scenes.
Related
Context
Greetings,
One day I randomly found RethinkDB and I was really fascinated by the whole real-time changes thing. In order to learn how to use this tool I quickly spinned up a container running RethinkDB and i started making a small project. I wanted to make something very simple therefore i thought about creating a service in which speakers can create room and the audience can ask questions. Other users can upvote questions in order to let the speaker know which one are the best. Obviously this project has a lot of realtime needs that i believe are best satisfied by using RethinkDB.
Design
I wanted to use a vary specific set of tools for this. The backend would be made in Laravel Lumen, the frontend in Vue.JS and the database of course would be RethinkDB.
The problem
RethinkDB as it seems is not designed to be exposed to the end user directly despite the fact that no security concern exists.
Assuming that the user only needs to see the questions and the upvoted in real time, no write permissions are needed and if a user changed the room ID nothing bad will happen since the rooms are all publicly accessible.
Therefore something is needed in order to await data updates and push it through a socket to the client (socket.io for example or pusher).
Given the fact that the backend is written in PHP i cannot tell Lumen to stay awake and wait for data updates. From what i have seen from the online tutorials a secondary system should be used that should listen for changes and then push them. (lets say a node.js service for example)
This is understandable however i strongly believe that this way of transferring the data to the user is inefficient and it defeats the purpose of RethinkDB.
If I have to send the action from the client's computer (user asks a question), save it to the database, have a script that listens for changes, then push the changes to socket.io and finally have the client (vue.js) act when a new event arrives, what is the point of having a real-time database in the first place?
I could avoid all this headache simply by having the Lumen app push the event directly to socket.io and user any other database system instead.
I really cant understand the point of all this. I am not experienced with no-sql databases by any means but i really want to experiment with them.
Thank you.
This is understandable however i strongly believe that this way of transferring the data to the user is inefficient and it defeats the purpose of RethinkDB.
RethinkDB has no built in mechanism to transfer data to end-users. It has no access control (in the conventional sense) as well. The common way, like you said, is to spin up one / multiple node instance(s) running socket.io. On each instance you can listen on your RethinkDB change streams and use socket.io's broadcast functionality. This would be a common way, but as RethinkDB's streams are pretty optimized, you could also open a change stream for every incoming socket.io connection.
I´m going to create a web service for learning purposes and wanted to combine it with my WoW Hobby. My goal would be to create a "simple" Addon, which tracks my battleground activity in real time.
So when queuing for AB it enters my data in an db and when I´m out of the BG it should delete the db entry. The information should be stored in an JSON/XML-File and whenever the bg-status changes it should execute the post/update on the DB on the RESTful service.
The real time communication is very important here and I would like to know which ways of communicating to a web service are available, so I could directly dive in and create a solution.I´d like to have resources instead of solutions.
Currently I´m not used to LUA, but would like to learn it to get the knowledge of creating such a service.Which sites are you suggesting for learning LUA, especially the WoW-API?
Addons only write to disk when you log out of a character (and read that saved data when you log in) so what you intend would not be possible.*
More involved ways of communicating with the rest of the computer or even the internet are prohibited to prevent the gain of certain advantages, an example would be looking up details about your Arena opponents.
* Well, there are certainly some ways, but rather complicated ones: a program monitoring sound output to check when the BG queue pop sound is played, or a screengrabber that registers when the BG score screen comes up (which can be viewed during the match though, too)
I have the ecommerce store.
I faced automatization problems as my business growing.
My website is written in PHP on Kohana Framework.
I want to automize many processes, but do not know where to dig deeper.
Example:
When order is recieved I want to fire the event "order.recieved". This event knows that my system needs to fire subevents and other actions:
to log inventrory changes asynchronously;
send to the procurement module out-of-stock products and their quantity;
to recreate sliced inventory table asynchronously;
send real-time message to crm system that order is recieved;
send sms to the client with message "We will call you soon";
etc.
Solutions I have in my head:
1) I think the simplest way is to rewrite my application on Laravel framework with it's event dispatcher.
Challenges:
I want use fifo (First In, First Out) for the inventory change;
I need digging to the code to know how many events I have in my system, when they are used,
2) Use AMQP Middleware like RabbitMQ.
Challenges:
I need digging to the code to know where exactly message is sent;
Maybe It can be solved with some event dispatcher, but ->;
Again, I need digging to the code to know how many events I have in my system, when they are used
Are php workers/consumers good to handle messages? Or I need to use python, nodejs?
Challenges:
I need to have many php workers/consumers. I think PHP is not good to handle this.
3) Use some webhooks management system.
4) Study more and use some bpm engine. Only one thing I know right now I can benefit using business rule engine for complex discounts.
What solution I need to take and get deeper with it?
I am wanting to give back to a small gaming community. The idea is to make an app that acts like a chat client to connect to the game servers. I am trying to grasp the concepts on how connections work through examples I've found on the web, since I am self taught by seeing examples.
So far the examples I found are for connections on the same network. What I need is some kind of example that will allow me to connect from different networks or at least an explanation on what I need to do. Also I need to be able to get around a router without with setting port forwarding on the router.
In the end the app will be connecting to the game developer's server but I need a working app before I get his permission to connect to his servers.
Any help will be most appreciated. If any additional information is needed to help just ask and I'll do my best to fill in the gaps.
That is a very broad question, but I try to give you as much information as possible from by point of view. As I'm not yet sure if you want to have a P2P Connection (game-application to game-application) or a standard server model, I will just mentioned different approaches to this problem.
Adobe has support for P2P since a long time. Read some FAQ, esspecially "How does RTMFP differ from RTMP?" (I try to choose Sources with infographics, as that helped me to understand it).
What you really should start playing with and making first steps in, should be NetConnection. This is the very basic Function that will allow you to communicate to a Server running e.g. PHP or connecting to a Flash Media Server (FMS). FMS is inpartcular interresting for you, as it really boosts the ideas what you game could do, but setting up a FMS is not that easy,to host a own instance is even more complex. So if you come to the conclusion that you want to travel the road of using a FMS, I can suggest you Onyx Server. They mainly marketing theirself as a Streaming service, but in reality you will get access to a FMS for a ok'ish price (FMS instances on Amazon were way worst the last time I checked).
The FMS basicly only a Flash AS2 File with some extra Commands. Your FMS can handle real-time (!) persistent connections (!) with any client that connects to it. Everyone is able to connect to the server at first, and you can then choose in your FMS Script what a client have to bring to the table to stay on the server or is rejected. After that, you have a very string tool for a Game. For example, you could have a game instance connect to it, tell the server that an enemy was hit and the server near-instantly (the speed is really amazing, there is no feeled delay, it really is instant. Its called SharedObjects) pass this information down to the enemy game instance. I used FMS only for one project and it was a very long ride to understand it and work with it, but it was a really nice experience, as you code the Server in the "same" language like the game itself (AS2, AS3 = ECMA).
If you dont want to spend money at this stage, you can use the Adobe RTMFP Instance at p2p.rtmfp.net. It is, as far as I know, only for testing and you will be rejected if you misuse the service for a real project, but for starting and testing it will do. If you use the Cirrus Engine, you can even follow this Tutorial. You will find sample code in there:
// Cirrus connect info
private const SERVER:String = "rtmfp://p2p.rtmfp.net/";
private const DEVKEY:String = "{YOUR_DEVELOPER_KEY}";
// Used to connect to the Cirrus service
private var _netConnection:NetConnection;
_netConnection = new NetConnection();
// Listen for status info
_netConnection.addEventListener( NetStatusEvent.NET_STATUS, onNetStatus );
// Connect to Cirrus using our unique URI
_netConnection.connect( SERVER + DEVKEY );
My adive for you would be: Try getting comfortable with NetConnection. It is really straight forward. When I first started using it, I had a couple of days struggeling and reading a lot on the web, but I learned a lot doing so. You should too. Use NetConnection and try to create two simple AS3/FLA instances of your code that both connect to the same domain (use the adobe rtmfp domain for now) and try to exchange some simple String-Data between these instances.
To take some of the pain of your shoulders, add the minimum amount of listeners to your NetConnection like so:
//Main NetConnector
nc = new NetConnection();
//Troubleshooting Listener
nc.addEventListener(SecurityErrorEvent.SECURITY_ERROR, securityErrorHandler);
nc.addEventListener(NetStatusEvent.NET_STATUS, status_handler);
//nc.objectEncoding = ObjectEncoding.AMF0; //Default
nc.client = this;
nc.connect("https://some-domain");
////////////////////////////////////////////////////////////////////////////////
/// CALL ERROR LISTENER
////////////////////////////////////////////////////////////////////////////////
private function status_handler(e:NetStatusEvent):void {
//trace("NetStatusEvent");
dispatchEvent(new CallEvent(CallEvent.CALL_NATIVE_NET_STATUS, e, true ));
}
private function securityErrorHandler(e:SecurityErrorEvent):void {
//trace("SecurityErrorEvent");
dispatchEvent(new CallEvent(CallEvent.CALL_NATIVE_SECURITY_ERROR, e, true ));
}
You will get alot of errors and netStatus and NetSecuriy Events. Flash will often run into Sandbox-Violation errors when you now know what you are doing. That can be frustrating but if you keep it up, google every error and compare you implementations with the implementation of others, you will wrap your head around this and can do really neat stuff with it.
I recommend you google sources and tutorials for NetConnection and stick to one that is on your level of knowledge.
Good Luck.
I'm working on an iPhone application that should work in offline and online modes.
In it's online mode it's supposed to feed all the information the user enters to a webservice backed by GWT/GAE.
In it's offline mode it's supposed to store the information locally, and when connection is available sync it up to the web service.
Currently my plan is as follows:
Provide a connection between an app and a webservice using Protobuffers for efficient over-the-wire communication
Work with local DB using Core Data
Poll the network status, and when available sync the database and keep some sort of local-db-to-remote-db key synchronization.
The question is - am I in the right direction? Are the standard patterns for implementing this? Maybe someone can point me to an open-source application that works in a similar fashion?
I am really new to iPhone coding, and would be very glad to hear any suggestions.
Thanks
I think you've blurring the questions together.
If you've got a question about making a GWT web interface, that's one question.
Questions about how to sync an iPhone to a web service are a different question. For that, you don't want to use GWT's RPCs for syncing, as you'd have to fake out the 'browser-side' of the serialization system in your iPhone code, which GWT normally provides for you.
about system design direction:
First if there is no REAL need do not create 2 different apps one GWT and other iPhone
create one but well written GWT app. It will work off line no problem and will manage your data using HTML feature -- offline application cache
If it a must to create 2 separate apps
than at least save yourself effort and do not write server twice as if you go with standard GWT aproach you will almost sertanly fail to talk to server from stand alone app (it is zipped JSON over HTTP with some tricky headers...) or will write things twise so look in to the RestLet library it well supported by the GAE.
About the way to keep sync with offline / online switching:
There are several aproaches to consider and all of them are not perfect. So when you conseder yours think of what youser expects... Do not be Microsoft Word do not try to outsmart the user.
If there at least one scenario in the use cases that demand user intervention to merge changes (And there will be - take it to the bank) - than you will have implement UI for this - than there is a good reason to use it often - user will get used to it. it better than it will see it in a while since he started to use the app because a need fro it is rare because you implemented a super duper merging logic that asks user only in very special cases... Don't do it.
balance the effort. Because the mess that a bug in such code will introduce to user is much more painful than the benefit all together.
so the HOW:
The one way is the Do-UnDo way.
While off line - keep the log of actions user did on data in timed order user did them
as soon as you connected - send to server and execute them. Same from server to client.
Will work fine in most cases as long as you are not writing a Photoshop kind of software with huge amounts of data per operation. Also referred as Action Pattern by the GangOfFour.
Another way is a source control way. - Versions and may be even locks. very application dependent. DBMS internally some times use it for transactions implementations.
And there is always an option to be Read Only when Ofline :-)
Wonder if you have considered using a Sync Framework to manage the synchronization. If that interests you can take a look at the open source project, OpenMobster's Sync service. You can do the following sync operations
two-way
one-way client
one-way device
bootup
Besides that, all modifications are automatically tracked and synced with the Cloud. You can have your app offline when network connection is down. It will track any changes and automatically in the background synchronize it with the cloud when the connection returns. It also provides synchronization like iCloud across multiple devices
Also, modifications in the Cloud are synched using Push notifications, so the data is always current even if it is stored locally.
Here is a link to the open source project: http://openmobster.googlecode.com
Here is a link to iPhone App Sync: http://code.google.com/p/openmobster/wiki/iPhoneSyncApp