A good framework to make multiplayer shooter for your mobile devices

There are many things you can use off the shelf but the basic setup is very simple but you have a few options.

The most common is server push, things like Flash Media Server, LiveCycle Data Services from Adobe or other tools like SmartFoxServer can do this. With this setup the server saves the connections to everyone that connects to the server and passes or "pushes" applications state to the people connected every time the data changes in the application.

Another option is called long pulling, this can be done with any web server really. How this works is the data stores the state of the application, when the application starts it calls the server, when it responds the client calls the server again.

There are a few other ways to do it but these are the most common. But this has nothing to do with protocol like HTTP, UDP, AMF, XMPP, or whatever else. The protocol is the format that the data is sent. With these out of the box servers they normally output a few of these but the fastest formats are binary like AMF but not always the best, there are advantages to each, because each gives you different features for keeping track of things.

If you are talking about have a game that takes over the world that has millions of users then you need to think about scaling and what happens when you need two or 100 servers and how do they talk to each other. But for now keep in mind that the more the server does the slower it will get, if you are sending small amounts of data it will be able to handle more users. Stick with making one efficient server and worry about that later if you get there.

You also need to thing about what server side programming language you want to mess with if any. Some services don't let you do anything, these normally cost money and don't do as much. Adobe likes Java but there are servers that output all of these protocols in most every language. My favorit lately has been Node.js a super fast way to run JavaScript on the server. Node.js has a built in HTTP server but it is just as easy to create a simple server that sends basic text through a Socket or XMLSocket. A server like this will easily handle many thousands of users. There are many games that use Socket.IO and if you want to see a simple example of what I'm talking about you can check out this.