65
votes
What's the performance benefit of saving all logged in characters in MMOs in regular intervals?
This is not for performance. This is a failsafe. If the world saves every few minutes, then if something happens to the server and it shuts down everyone will only lose a few minutes' progress.
By ...
- 595
49
votes
Accepted
How to handle a large number of pickups in a MMO game
By simply only loading those parts of the world into memory which are close to the player. Anything else is suspended to hard drive. When there is a tiny object laying around two kilometers away, then ...
- 121k
43
votes
How does delta compression reduce the amount of data sent over the network?
There are times when you cannot avoid sending the full game state - such as on load of a saved multiplayer game, or when a resync is needed. But sending full state is usually avoidable, and that's ...
- 30.2k
33
votes
Accepted
Acknowledgement reliability using UDP
This is a form of the Two Generals Problem, and you're right - no number of retries is enough to perfectly guarantee receipt.
In practice in games, there's usually a time horizon beyond which the ...
- 136k
24
votes
How does delta compression reduce the amount of data sent over the network?
You have the wrong delta. You're looking at the delta of the individual elements. You need to think of the delta of the entire scene.
Suppose you have 100 elements in your scene, but only 1 of them ...
- 994
22
votes
How to handle a large number of pickups in a MMO game
You have two very different things to manage:
The server must manage the entire world, in an authorative manner. For that, communication with N clients (where N is "massive") is necessary.
The client ...
- 1,384
13
votes
Accepted
What is the difference between a "ping" and "RTT" (round-trip time)?
A ping is a method to measure round trip time.
The process of "pinging" is to send a "ping". A "ping" is a network message which serves no other purpose than to get an immediate response from the ...
- 121k
12
votes
Should damage calculation in a competitive multiplayer game be done client-sided or server-sided?
Rule number one for multiplayer netcode design: Anything that matters for gameplay should be calculated server-sided. Never trust the client. The client is in the hands of the enemy. You can not ...
- 121k
11
votes
Should damage calculation in a competitive multiplayer game be done client-sided or server-sided?
Option 3: The client sends a click event to the server, the server decides where this click event has landed, decides if there is a hit or a miss, then applies the damage and sends the updated world ...
- 16.3k
9
votes
Accepted
How to compensate for moving objects with client side prediction?
During the 6 months since I asked this question, I ended up developing a complete open source game server to deal with this exact issue (and many others!): https://lance-gg.github.io/
The R&D ...
- 655
9
votes
How does delta compression reduce the amount of data sent over the network?
Very often another compression mechanism will in combination with delta encoding like for example arithmetic compression.
Those compression schemes work much better when the possible values are ...
- 7,496
9
votes
Acknowledgement reliability using UDP
The approach TCP uses is that the sender will keep resending the packet until it receives an acknowledgement. The receiver will ignore duplicate packets, but still send acknowledgements for them. The ...
- 630
8
votes
Accepted
Why do multiplayer games/chat services ever need to be able to open all NAT ports?
Just to make sure we're all on the same page in terms of terminology:
What is NAT?
NAT is an acronym for "Network Address Translation". It's a system designed to allow a router to allow a ...
- 21.4k
8
votes
Accepted
Where should multiplayer games start? Client or server?
You develop both at the same time, inside the same executable or a DLL loaded by the game executable.
The game always run on a server, even when running single-player.
When running single player ...
8
votes
How does delta compression reduce the amount of data sent over the network?
You are right that a naïve delta calculation on its own, with the result stored in the same size data structure as the operands and transmitted without any further processing would not save any ...
- 178
8
votes
How does delta compression reduce the amount of data sent over the network?
You are broadly correct, but missing one important point.
Entities in a game are described by many attributes, of which position is only one.
What kind of attributes? Without having to think too ...
- 20.2k
7
votes
Accepted
Networked projectiles in an authoritative server
This is what we ended up doing:
Client side
Detect player clicks button to shot missile
Immediatley simulate rocket visuals on client
In parallel, send command to server
Once predict hit something, ...
- 676
7
votes
Accepted
Client side prediction physics
Client-side prediction depends very heavily on a deterministic physics model that exactly replicates the way the game object behaves on both the client and the server. Even small floating point errors,...
- 128
7
votes
Determing winning on the server side or client side?
Hello visitors of Jindsay's Card Game Forum. Here is your friend xXx_GameH4x0rPhilipp_xXx with another cheat for you. Do you want to win every game? Here is a simple hack which works with every web ...
- 121k
7
votes
Acknowledgement reliability using UDP
If you want to reinvent TCP, it makes sense to look at TCP first, which deals with the exact problem you describe (part of the solution is to use user defined values for retry attempts and timeouts).
...
- 9,955
7
votes
Accepted
Architecture of networked game engine
TLDR - start simple and build up. Getting to AAA quality networking in an action game is complicated but may not even be necessary for your game.
So basically: When client connects to the server, ...
- 41.9k
6
votes
Accepted
Resolving prediction error from client side prediction and server reconciliation
I solved the problem on my own. My previous implementation of the networking engine made reconciliation impossible. The code I am using is private, though I plan on open sourcing the Box2D server/...
- 332
6
votes
Accepted
Network protocol for chat -- UDP or TCP
When it comes to chat systems, reliability is far more important than latency and bandwidth. That would usually make it a typical TCP/IP use-case. However, using both TCP and UDP in parallel through ...
- 121k
6
votes
How does delta compression reduce the amount of data sent over the network?
While most answers talk about how delta encoding is about only sending the changes to state as a whole, there is another thing called "delta encoding" that can be used as a filter for reducing the ...
- 407
6
votes
Accepted
Why is server frame rate slower than client's?
It's not necessary. The reason why you need 60 FPS on the client is because you want the animations and movements to look fluent. But when it comes to just the game mechanics, 20 FPS is more than ...
- 121k
5
votes
Accepted
How to organize messages queue in a fast-paced multiplayer game
You should implement your UDP reliable as TCP.
On http://gafferongames.com/ you can read about packing packets, resending them, correcting errors. There is some pseudo-code (or this is written in C, ...
- 2,552
5
votes
Does it make sense to use both TCP and UDP at once?
Here's a quote by Sam Jansen from a comment on gafferongames.com:
Speaking as a network researcher and not a game developer, the conclusion to never use TCP and UDP together seems a bit strong. TCP ...
- 699
5
votes
Accepted
How do MMO servers handle a large concentrated number of players?
Are you already familiar with technologies that exist like redis? Server architecture is definitely a complicated subject and it's good that you're planning it out now, but you might be worrying ...
- 165
5
votes
Determing winning on the server side or client side?
Doing basically anything on client-side apat from the inputs is a bad idea. And believe me, if the programmers could collect inputs on the server side, so the client couldn't fake them, then they ...
- 15k
Only top scored, non community-wiki answers of a minimum length are eligible