I want to create 2d multiplayer with game mechanism similar to slither.io/agar.io . I've done some reasearch and i'am not sure what technology should i use:
Java: http://netty.io/ + jbox2d or http://netty.io/ + liquidfun (Is there something better than netty for web communication ?)
or
c++: box2d original implementation +? (I didnt find any suiting web-comunication library. Please let me know if you have knowledge about some stable and suported library like netty).
You may want to look into Node.js and see how it might be able to replicate the games your talking about. Using node in your project lets you do a full stack implementation of any one of these games using a single language. If your interested I have a proof of concept server running that tracks the movement of a couple of balls.
The next steps would be to implement physics which I have used box2d with JavaScript before so it wouldn't be that difficult. Looking on npmjs.com there are a couple of package available that support the box2d library. Lucy-b2 looks like it might work and the author wrote up some decent instructions.
Also if you are interested I've been writing a tutorial series talking about this very subject using JavaScript, canvas, and Node. Just PM me and I'll send you the links to the proof of concept server and my tutorials.
If you are already familiar with a specific language or engine it would make sense to go with that. Otherwise you can take a look at Unity3D.
@lede I've made alpha version of my game with node.js and this https://www.npmjs.com/package/box2dweb box 2d implementation, but unfortunately it comes out that this js-port has some memory leaks. Jbox or liquid fun seems like more stable libraries and they are faster than js ports because math stuff works better in vm or in c++. Are you sure that Lucy-b2 has no leaks? If i was sure that creating my game in node will be stable and fast considering a little more sophisticated physics than agar.io then i would chose node.
