I have developed a simple two player chess game in android to be played using Bluetooth. I want to extend it by making it possible to be played through internet. whenever a player makes a move, the move should be transferred to the other player via internet.
How to make this possible?
I have heard of C2DM mechanism.Does that suites the scenario i described and is it reliable?
Thanks:)
Yes, C2DM is ideally suited to this type of game. This is what I am using for my own game (http://www.chesspresso.net) which is a correspondence chess client for android.
Things to consider when using C2DM:
You don't send the info to the devices, you notify the devices that a move has been made. You don't use C2DM to transfer data, you use it to notify that something has changed.
Its available for 2.2+ Android, which is the majority of devices. But if you wanted to support older devices you'd have to consider an alternative. I am using polling for older devices.
You have to request for developer access, then once your app is ready you have to request production status. If you don't do this you'll hit the developer status quota very quickly once its released! They are very generous with production quota, but you have to explain what you're using it for and it also can take a few weeks to get accepted!
Your users will have to have a google account that is authorised, otherswise C2DM won't work. Most users will have an account associated with their device, but some don't so this means that you'll possibly want to validate for the presence of an account to notify the user.
Its reliable, but every now and again a device will have to wait for the message. Sometimes a few minutes. Usually its instant.
Hope that helps!
UPDATE:
C2DM has now been deprecated, and replaced by Google's GCM.
Also, I strongly suggest looking at other options as tying yourself down to a Google specific API means you won't be able to support external marketplaces. For alternatives, I am currently evaluating Amazon SNS and I will also be looking at Urban Airship. There are possibly other alternatives I have not considered evaluating yet.
UPDATE:
Evaluation update of non google based push notifications:
Amazon SNS is just not a project for this task and Urban Airship for the vast majority of apps is too expensive. Unfortunately all the other alternatives are all very expensive also, especially if your app (like mine) relies heavily on push.
A good way of doing that is using a simple direct TCP connection between the peers.
If you're new to socket programming on Java, try this:
All About Sockets
Another option is to use some sort of IM as a communication medium for app. For eg. Use Asmack to connect to XMPP Im like GTalk. Prompt user to create an account there, for your game.
And use it to send and receive commands via IM. This way you won't need to setup your mediating server.
This works if user knows who he is playing with. To collect the user data and let them search for available players, you still need to setup a server. IRC chat room may be an option to avoid this also.
GTalk was just an example. You can use any IM or IRC also.
C2DM it's not design to transfer informations, even if they are small like "horse in b4" or things like this. It's designed to inform the device of something, maybe a newer version of a document or more articles on a website.. Stuff like this.. It's not designed to communicate device to device. And also it may be not fast enough for a real time chess play.
You should look for a more traditional way of communicate via internet or to search for some libraries (I'm pretty sure that something exists..) that will help you.
IMHO, C2DM is exactly the kind of thing you would want for a chess game; to be notified when the oppo has made his turn (which may be minutes /hours / days later ?). I have discussed my game with a few google android devs and they've stated that C2DM is ideal for this. You'll need to go via a centralised server though (well, not essential but very advisable) as there may be issues with resync'ing game state etc. Worried about "hitting the limit" ? Well, for a start my c2dm acct is restricted to "just" 100,000 messages per day. I guess you're buying the drinks if you hit that !!
Chess is often played by email. You could do that.
Of course, any centralized/federated messaging system will work.
What might be better for your use is to add a jabber client to the application and have the program generate an account name that is used for automated messaging. You could host the jabber server or generate the accounts on a free provider.
Google App Engine if you know Python or Java.
Alternatively there are two web app API styles in wide use today: SOAP XML and RESTful web services.
If you know RoR I would recommend using JSON/REST, because you can just use Phusion Passenger with Apache to deploy your app. Free, extremely easy, and makes your server very reliable.
You could, and I only mention this because my friends do this all the time, use twitter as a server between the games.
I also found a lib called mages which looks quite promising.
Good luck.
I did this for my online 2D rpg: http://developingthedream.blogspot.com
Basically, use a middle-man server to co-ordinate data between all your clients.
You simply open a socket and communicate with the middle server and it takes care of passing on the information to any other connected clients.
I wouldn't recommend C2DM because of the message limit, and because the latency is still to big. Using your own server you can optimize it, plus you'll be the only one using the service so your data will be delivered faster.
I think that C2DM is not right way for playing chess because there is no warranty that messages will be delivered. You need more reliable way for data transfer
Related
I am making a chat application for android. For that, I decided to use GCM (Google Cloud Messaging). But having researched a bit about it,I have read that it shouldnt be used for something like chat.
I will be implementing Upstream messaging (sending data from the device to the GCM directly, without a send-to-sync). Here are my concerns:
Will the messages transfer instantly? (will be fast enough that the user can see 'typing'/seen)
If all devices are online, what is the guarantee of the message from GCM reaching the client.
The main reasons I want to use GCM is
GCM uses the least amount of battery life
This is an android-only app.
If GCM is not what I should use, what should I use?
I am working on a similar requirement and Looking at the requirement of being able to show feedback such as typing/lastseen etc, as per my knowledge XMPP based solution would be appropriate.
you can try with available xmpp server like ejabberd/mangooseim (open source) by installing it on your server and use asmack or any other client side java library to communicate it with your server. (There are lot of tutorials available for this).
With this much setup you will be able to get to the stage where you are able to get status such as "typing", "gone" which whatsapp and also some chat clients like gtalk/pidgin shows.
It would roughly give an idea of how existing chat clients work.
Ejabberd is completely written in erlang and if you want to extend any functionality erlang knowledge is must. (it is specifically designed for highly concurrent fault tolerant and non-stop systems, which was helpful in chat applications.
GCM would be definitely able to communicate between the android phones 99.99%of times with not much delay but if you want to have roasters status like normal chat applications, you will have to reinvent the wheel completely.
Update:
Here are the considerations.
from client A to client B I want to send chat messages with roasters and dont require to store messages on any central server but just on the clients - XMPP (like whatsapp)
in case you require all the communication to be stored in server - XMPP with sql driver or mongodb driver / gcm (Depending on your time and resources)
in case you require communication between devices not necessarily chat, then gcm should be sufficient.
I am using this approach in my app currently which is live on playstore with beta version and it absolutely works fine in most of the cases. I havent seen much of bottle necks as of now.
I'm creating a viber-like application, i.e. android users can make instant messages in their android-powered devices. I've created client-to-server webservices using ASP.NET (ASMX service with JSON response) and it works like a charm, but the other side, i.e. server-to-client requests is just a little headache. Of course I can make my application so that there is no need to server-to-cliend requests (sending dummy requests from client to server in short periods) but in this way server will be overloaded specially when number of users increases. I've found some technologies regarding instant messaging, including GCM and XMPP. What are my other options? or let me ask what is my best option?
Should I use sockets? If so, how can I always have my clients IP (considering that clients are mobile users which may be using WiFi or GPRS/3G/4G internet). I'm thinking of a system in which my clients send their IP each n seconds (n can be around 30), so server always has a (nearly) up-to-date list of client IPs.
Is it possible or even logical to do so?
You should definitely consider using GCM (Google Cloud Messaging for Android)
You need to setup a few things in your server to be able to use it to send via GCM.
Its the built-in way to send data from a server to an android device, hope this can help
Implementing GCM Server
Using the good old strategy of long-polling is always possible, but there are much better ways to do it nowadays. That's perhaps the fastest to implement of the mentioned (not so if you want to implement it correctly and with min amount of load on your server/DB engine). I've seen some projects that start around that architecture with the idea to move to something better in the future .... and the moment to move never comes of course. If you start browsing your Android phone connected to a proxy like Charles you'll see what I mean :)
WebSockets are an option, but I don't see a reason why I'd use them for a Viber-like app, which is event-based (you've received a message) and not "real-time" (monitoring some stock graphics movements for example).
Your best choice here is a Google Cloud Messaging (GCM)! It's easy to implement it both on your backend and on the client, and it's built specifically with the problematic connectivity in mind (switching between wifi/poor 3g/4g/etc). It has some pretty nice features that other methods don't provide "out of the box" - message resending (the common scenario of a client loosing his connection - GCM it'll send the push notification later, when he comes online), automatic syncing between devices (smartphone, tablet, etc) and others.
I am conceptualizing an Android app that sends data from one device to another (like a picture message), but because I do not have a server, I am looking into other ways of messaging. Google Cloud Messaging (GCM) seems like a good choice, since its made for Android, and is free to use, but it still requires a server to use. Is there a way around this requirement- such as running the GCM server on the app itself? Or is there a better approach to serverless messaging on Android?
Yes you can - it's possible to send the same messages from a device that would be sent from a server. However, this has the following problems:
You're putting your API key in your app, so somebody could decompile your APK to get it.
Your users would need some way to share their GCM registration IDs with each other. If two users had both their IDs expire at the same time, there would be no way to share them again.
Really, building your app and hosting it on AppEngine would take about an hour to write, and cost less than $10 a month, even for a ton of users.
For a dead-simple messaging server example written in Java, check out the server backing one of my apps:
https://github.com/charlesmunger/touch-to-text-server.git
I think that will be hard to do what you want effectively without a server but you can check out Parse's SDK. It is free to try and free up to a certain monthly limit.
The docs.
You may want to read "Sending Pushes to Channels" and "Using Advanced Targeting".
I noticed that Google C2DM quota is limited to 200000 messages per day. This makes me thinking that it should be used for very simple use cases. Now I understand why IM services like skype or others have a service always running on the background. Does a library exist to manage a persistent connection to the server? I have tried XMPP with Smack api but even if it is very good for desktop stable connections, it is not so suitable for mobile ones (that have many problems). I would prefer a simpler one specific for mobile applications. Does it exist?
Thanks
What are you trying to do here? Google C2DM quota is a soft-limit. If needed, you can email them and perhaps agree on some sort of business deal with them.
If you are looking for push-like experience, you can check out Urban Airship. They made their version of service that works on the Android devices without C2DM support.
I would recommend checking out Deacon. There is Android specific code and it runs as a service in the background with a connection to your server.
I am an android developer and I made some board games. Now i want to make some of my board games multiplayer. I don't want to create and host my own web service, so i thought about P2P.
The first thing i found was the XMPP protocol, however it's not real P2P, but if i can use the existing google talk service, i'm ready to go. Is this possible while using your existing google account without interfering with the normal working of your google talk client?
Then i heard about JXTA, a real P2P solution, and it's already ported from J2ME to Android (http://code.google.com/p/peerdroid/).
Maybe i am overcomplexing things here (as i do sometimes)
I just want to know the easiest way to do simple P2P for a boardgame.
All your opinions are welcome! Thanks in advance
Kristof, Did you get an answer to your question? I've been working on a multi-player application recently as well, though I've chosen to host the server (originally). I'm now reconsidering my choice, though, but the library I'm using fully supports peer to peer communications. The underlying protocol is built on top of Google Protobuf. It's essentially a full duplex RPC stack built on top of Netty, which can use Protobuf. Here's the URL to the RPC protobuf stack: http://code.google.com/p/protobuf-rpc-pro/
The author has been very helpful and I've found a couple of bugs, nothing major. I also had very little issues getting these libraries working on my Android phone, but they're not terribly "compact." Nothing extraordinarily large, just not small :). So far, I've had no issues getting the communications working both synchronously and asynchronously. As such, I may be moving my game over to a "peer to peer" style, and just provide the necessary location/registration server that would be used to find existing games/server.
Using XMMP should be possible for you case. Look at smack from igniterealtime. They have a nice and active java api that helps to build you own jabber extension packets that can be used to transport the changes in game state.
I think that using two google talk clients at the same time with the same account could be difficult. But it would be great because you could invite all the friends from you list to play with you directly from your game. This way you could easily get more people to play your game.
You can't use the existing Google Talk Service/Connection from what we've seen. You should take Janusz's advice and check out the smack library, that's your best bet. To allow multiple non-interfering connections with the same GTalk login take a look at the resource component of the XMPP address, it's what allows you to be logged into two clients at the same time to the same account. You can effectively make your game another client. More here: http://code.google.com/appengine/docs/java/xmpp/overview.html#JIDs_and_Resources
Finally, there appears to be some new functionality in 2.2 relating to device push communication, but I haven't looked into it yet. 2.2 is not widely deployed yet either, so probably of limited use.
Basicly, if you want to write a multi user game or a game built on top of XMPP (Jabber), you should have a serious look at pubsub extension of XMPP. It's designed for pushing data from a server to clients, in the opposite way of HTTP. In HTTP the client has to pull information from the server all the time to be able to know when some new data is pushed. While XMPP is designed to push data to clients, when something happens. Less resources used on server and clients.
You should not use the Chat part of XMPP, as that will interfere with the users presence.
In pubsub you can create a tree of nodes, where clients can listen to any new data published in any node or subnod in the tree that the client subscribes to. So if some client publish data on one node, all clients that has subscribed to that node, or any parent, will be notified about this data.
The good part with XMPP is that it's extensible so you can extend the protocol with your own extensions. I also give you user authorization, authentification and encryption, and you don't need to debug that yourself.
You could use any XMPP-server with good support for pubsub or you can host one server yourself. There are plenty of servers usable for this. GTalk doesn't have support for PubSub last time I looked.