This is an edit of a question I asked about a week ago.
I'm working on an Android app which communicates with the users' home PCs to control some 3rd-party PVR software running on the PCs. The model is as follows...
Android app < - wifi/3g -> Windows Service <- localhost -> 3rd-party PVR software
The Windows Service is written by me (C# .NET) and acts as a proxy between the Android app and the PVR software.
What I'd like to do is use C2DM to notify users of various things - one example is if one family member sets a TV show to record, a C2DM message is sent to other family members' devices so everybody is up to date.
I now seem to have 3 possible options for how to proceed. The Windows Service is a key player in the system so plays a part in them all but I don't know what the best approach is.
Use the Windows Service as the C2DM 3rd-party app server. Downside - I need to embed my C2DM credentials into the software and there will be potentially 100s of servers around the world requesting authentication tokens (not sure if Google would allow that).
I have a hosted web server I could use which allows PHP/MySQL. The Windows Server would simply act as a relay but my PHP experience is minimal and I can't find any comprehensive PHP examples for C2DM.
Use Google App Engine (again with the Windows Service as a relay). The problem is I don't know if Google are happy with GAE being used as a C2DM app server although I've seen a few mentions of it.
I've basically Google'd until my head hurts and keep coming back to the same tutorials and partial code examples. I know how C2DM works and actually have option 1 working in my dev environment but it doesn't seem like a good option to go public with.
So (trying to keep my question as objective as possible)...working on the principle that option 1 is not a good idea, are there any reasonably comprehensive PHP examples out there for a C2DM app server or, alternatively, does anyone know definitively if GAE is an acceptable approach?
With C2DM you can target the device that the message goes. So in you example the one that sets the TV show sends a message to the Windows Service to notify each one of the other users.
You can do that with 1 C2DM server
UPDATE
I whould go with the 3rd server.But of what i can tell you are not sure about the structure. Shared now GAE later maybe finally ec2. What can you actualy do is to create a CNAME that points to the server of choice.(less hard coded). I don't think that GAE cannot be used for C2DM. It's a simple server with http requests.
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.
What I'm trying to achieve is a connection between a users browser (logged in with his Google account) and an Android application on his phone (also logged in with the same Google account). I want to send a bunch of text formatted as JSON from GWT to the device and the other way round too.
My first thought was to send a C2DM ping to the Android devices and wake up a service witch connects to the App Engine server or the GWT client directly (if that's possible).
What I'm doing now is a socket with the Channel API from GWT to App Engine. And for a large amount of text I would just send a notification via the Channel to the GWT client, which then gets the data with a RPCall. Missing is the connection between the App Engine and the Android application. What I could do is C2DM for one direction and simple HTTP requests for the other direction. I don't like this solution, because C2DM can be really slow some times. Is there a solution to connect these two (GAE & Android app), or even a better without App Engine and a connection between the GWT client and the Android client directly ?
Thanks in advance :)
If I understand your question correctly, you're looking to push messages from a server (in your case GAE) to an Android app without using C2DM? In that case you can give pubnub a try.
Edit: of course you have a few options in this area (another one being Urban Airship) but you'll notice that they're not cheap!
I'm not sure what you mean by "a connection between GWT and Android directly" -- do you mean a connection between a GWT client and an Android phone? If so, there's not a good way to do that without installing client software; you'll need some sort of server to proxy messages.
So, given that you're using App Engine and GWT already, and C2DM is potentially too slow, you could wrap up an HTML page on the Android and use the Channel API. Then when you get messages, have your javascript client (again, running on Android) call the container to do anything you want.
This is nice because you have parity in the message delivery between your browser clients and your Android clients. It's not nice because it's not native and probably will eat battery, unlike C2DM.
Ideally I know you'd like a native API for Android to consume Channel API messages. You can vote for this issue but I unfortunately can't provide an ETA for it: http://code.google.com/p/googleappengine/issues/detail?id=4189
There is a Google+ mobile application for Android. To receive all the information it must be using some API.
How I can retrieve this information from my phone and see from where this app is getting data? I'd love to access it myself and see how it works.
You are talking about "reverse engineering" a network protocol.
Full sniffing
Get a market enabled emulator: How to install Android Market App on the emulator?
Get a network sniffer: tcpdump, wireshark, ...
Start to sniff what's going over the wire
http://www.thoughtcrime.org/software/sslstrip/ - an ssl stripping proxy
Inject your ca: http://www.mcbsys.com/techblog/2010/12/android-certificates/
This should, in theory, enable you to sniff any https or plain text connection.
Already available APIs
I would not try to hijack the connection. There is already a contacts API, it's called xmpp. You should be able to use the talk integration to pull your friend list.
Future APIs
You may also want to sign up for the upcoming API.
UPDATE
It appears that the Android client uses (at least partially) XMPP. The regular client requires an open XMPP connection and you can see a "RealTimeChat" in your logcat. It looks like the connection is encrypted because you get a "TLS required" message (the client seems to go through the XMPP connection states). I'm not sure if that's used for client based posts or just for server push. You can see the open connections with the help of "netstat". The connection goes away when google plus terminates.
I'd thus expect the API to be really open once released (or rev.eng).
UPDATE 2 (06. Jul. 2011)
Hangout is build on XMPP/MUC+JINGLE (muc == multiuser chat, jingle is roughly a SIP alternative on top of XMPP). And yes, they'll release the the details of it :-)
UPDATE 3 (06. Jul. 2011)
Multiple XMPP components for gtalk/gplus have been revealed by reading the JS code. It also emphasizes that they have build a great deal of features on XMPP.
They haven't launched the API yet. If there is something you want to build on Google+, they encourage you to signup here: https://services.google.com/fb/forms/plusdevelopers/
The API hasn't been released yet. Heck, the product hasn't even been released yet. Thats like developing a video game for playstation 5.
Yes it is. Its coming "soon" read :: http://www.webpronews.com/api-coming-soon-for-google-plus-2011-07
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