Where is wich part of the AI located at(Client-Server Games)

random · Post by **random** » Fri Sep 17, 2010 3:54 pm

Ok that might be is a silly question, but where is which part of the AI lodated at in a MMO Game.

For example, usualy the client will NOT receive the kind of command "move left leg from NPC XYZ now to an angle of..." AFAIK...

But where does the client part of the AI begins, will it receive the command "player in stage, spawn NPC´s" will it receive a command like "Player is close to NPC XYZ, advise NPC XYZ to attack" if the NPC now does have lifepoint, hitpoints, energy... something like that will the client receive a command like"lifepoints low on NPC XYZ make it attack more aggressive, make it flee... make it..." or are commands like that, those that describes the behaviour of a type of NPC, saved in the client itself, are there are conditions in the client like "if (NPC->getLifepoints() < NPC->getMaxlifepoints *20 / 100) NPC->actionFlee() ;", does the client even receive a command like "NPC[XYZ]->actionAttack()" or just the command "Player in Stage ... Spawn NPC".

Is there some kind of literature specificly about Online MMO Games where which part of the AI is located at.

thx in advance

kazymjir · Post by **kazymjir** » Fri Sep 17, 2010 5:00 pm

If you make AI at client side, don't be surprised when someone hack client and will make his lvl faster/get better items faster or will take other benefits by making that NPCs will not attack him.

By second, imagine that client side is old computer with slow configuration.
There is two players and one NPC. NPC is attacking player 1 with slow configuration and player 2 is watching everything.
For player 1 game very slows due to higher cpu load and everything is slower, but player 2 have faster computer and for him everything is fine.
Player 1 and player 2 will see different NPC actions, due to overload on player 1 side. For player 1 NPC will moving towar him, when for player 2 NPC will now attacking player 1.

NPC is just another player, but controlling by computer. It should be at server side and simulate other player.

slavik262 · Post by **slavik262** » Fri Sep 17, 2010 6:06 pm

It's all about abstraction. The server will never say "NPC #1 needs to move his right arm 45 degrees to swing his sword." The server just indicates to the clients that the NPC is attacking, and the client plays the animations.

random · Post by **random** » Fri Sep 17, 2010 9:19 pm

thanks for the replies, would you like to recommend me an opensource server software?
I have searched but so far apart from the usual application servers only http://www.reddwarfserver.org/?q=conten ... entation-0 server as open source found.

greetz

slavik262 · Post by **slavik262** » Fri Sep 17, 2010 9:41 pm

Games typically have their own proprietary networking code. You might want to start learning the basics about real-time networking, such as topic like the differences between UDP and TCP and how best to use them in a real-time application.

random · Post by **random** » Sat Sep 18, 2010 1:36 am

well i former programmed in java and actionscript, more webapplication like client server software where i used shared objects to communicate, i used a wether a tomcat application server or for media server issues the Red5 Mediaserver (opensource like flash media server derivat) which is based on Apache MINA Framework... both with a hibernate binding to sql.

I just thought there would be some opensource gameserver software with a ready to use API for the most common handling stuff, load balancing etc....

what about boost.asio?

greetz

kazymjir · Post by **kazymjir** » Sat Sep 18, 2010 2:50 am

Random, in this case everything is on more lower layer.
Check IrrNetLite, if you want to easily make networking in your Irrlicht game.
Anyway, you must learn about some things Slavik262 said, because it's really needed if you want to do network programming. Also, networking is very interesting topic

Lonesome Ducky · Post by **Lonesome Ducky** » Sat Sep 18, 2010 2:54 am

As the saying goes: "Never trust the client."

If you aren't looking for a network library but an already set up code base for game interactions between client and server, you might do best to look at some open-source multiplayer games.

Midnight · Post by **Midnight** » Tue Oct 05, 2010 11:03 am

Lonesome Ducky wrote:As the saying goes: "Never trust the client."

If you aren't looking for a network library but an already set up code base for game interactions between client and server, you might do best to look at some open-source multiplayer games.

OS (open source) won't get you very far, although you might find great examples of how to handle the basics the problem with open source is usually an utter lack of security. You might find the correct way to handle the flow of data but it won't be much for stopping hackers from abusing your systems.

The best advice anyone can give you is to use your head, and try to think like someone who is attempting to hack/abuse the networking format to their advantage. I have spent a great deal of time thinking about this subject and on many occasions you will find yourself in a catch-22 situation where doing it one way has it's flaws and doing it the other way presents a whole new set of issues.

As for the subject of TCP vs UDP the basic difference is that TCP works in an orderly fashion, where as UDP is all "random and stuff". But UDP is a very loose connection in the respect that it doesn't maintain a constant connection but rather "waits around listening like a CB scanner". IrrNetLite (which is legacy and unrefined) uses Enet, Enet is a UDP networking library which transforms UDP into something more like TCP as-in it orders the packets sent and is very useful for certain things. However Enet along with INL isn't a tried and tested library, and there is no support for the also legacy and abondoned code.

Although Enet or INL (irrNetLite) may be fine for games like RTS where you only have about 8 players maximum, it's not built to withstand proper scaling for something like an MMO which could be as simple as a MUD (multi-user dungeon) game.

When it comes to networking the only library worthy for game designers is custom code or RAKNET. You can purchase raknet for as little as $100 depending on how honorable you are it works on an honor system up to as much as $3000 if I remember correctly.

My personal intention was to develop a network lib specifically to solve this issue within the indie game dev movement, but until I build it over the coming year(s) there is no telling if that'll ever come to fruition.

At any rate, you are not fit to call yourself a network coder nor a game dev until you learn all of this yourself through years of experience. And although I'm not the only one this educated on the subject you'll find that most people are very reserved about telling you rather than attempting to motivate you to learn for yourself.

Do not use this in vain, take the others advice and actually LEARN how to program rather than constently seeking out all-in-one, easy-to-do, no-work-involved, free anything libraries.

Good luck, good reading, and happy coding.