Question

i’m currently programming an iPhone game and I would like to create an online multiplayer mode. In the future, this app will be port to Android devices, so I was wondering how to create the game-server ?

First at all, which language should I choose ? How to make a server able to communicate both with programs written in objective-c and Java ?

Then, how to effectively do it ? Is it good if I open a socket by client (there’ll be 2) ? What kind of information should I send to the server ? to the clients ?

Thanks for your time.

Answer 1

EDIT How massively multiplayer’ed will you game be?

Hi Cyril,

as you noticed, there are two main things two consider:

1. information sent to the server

2. information sent to the client

There’s only one type of information to sent to the server: the user inputs. If you don’t do that, you’ll encounter headaches over headaches when rogue client will try to send fake data to your server (like saying “My tank now has 100 000 000 armor”).

Then what you sent to the client is up to you but it’s totally possible to only sent to the client the other player(s)’s input. This is the way to have the absolute minimum and tinies bandwith usage possible. That is how games like Blizzard’s Warcraft 3 are doing it. As a bonus, this makes for tiny replay files (because all you need to do to be able to replay a game is the time (and the input) at which each player’s input happened).

The one downsides with sending only the other player’s input to the client is that it means all the game’s logic is present on every client. For some games, this may be an issue because people may cheat by reverse engineering your game and finding flaws. This issue can be mitigated with careful, controlled, randomization (where in addition to the input+time you send input+time+randomness where randomness cannot be guessed by the client in advance.

Another way to do it is to do some logic computation on the server side. Then, obviously, you need to send the result of the server computation to the client. Done correctly, this has the benefit of both preventing cheats and maky piracy impossible (for example nobody managed to play World of Warcraft in the real economy –that is, on the real Blizzard servers– using a fake licence key).

Regarding the phone-turn-based game server: just look at one top-selling turn-based game are doing it. Take Uniwar for example: works on iPhone and Android. Game server is written in Java “of course”.

The one thing to realize is that a game like the one you plan to write is entirely deterministic: if you can’t easily code a replayer or if you can’t easily reproduce any kind of scenario leading to a logic bug, you’re doing it wrong.

Note that being determistic doesn’t mean you can’t add what looks like randomness to your players: it’s simply that the randomness shall also be deterministic (for example by simply using a different seed for each game + the time at which player inputs are made as a fake random source).