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1500 Archers on a 28.8: Network Programming in Age of Empires and Beyond (2001)

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Re: 1500 Archers on a 28.8: Network Programming in Age of Empires and Beyond (2001)

#121

Post by reitzensteinm »

Emjayen wrote: post #119
reitzensteinm wrote: post #112

Earlier quoted context omitted.

That's not intrinsic to this style of netcode, though. Company of Heroes, for instance, just keeps the game running and your input is delayed until you can communicate it to the server. You'd generally want an authoritative server to accomplish this. Having it also execute the inputs prevents most cheating, too.

It is, in fact, inherent to this model. While there will be some tolerance threshold as to how far behind in the simulation a machine may fall, it still must be rather conservative (generally a few seconds), as elsewise the context (state-) sensitive inputs start frequently failing -- if I issue a command given at world-state time t , will it be meaningful/valid at state t2 ? The answer is where you get your threshol…

If it's not valid, just throw it out!

I've built and licensed a time traveling variant of this model (GGPO style) and spent years with thousands of concurrent users playing my games. And they operated just as I describe.

Company of Heroes is more of a traditional AoE style and will happily queue up unit orders for a minute or more while it attempts to reconnect or catch up.

Re: 1500 Archers on a 28.8: Network Programming in Age of Empires and Beyond (2001)

#122

Post by bluescrn »

taberiand wrote: post #47
paulryanrogers wrote: post #36

Earlier quoted context omitted.

If the randomness is deterministic doesn't that mean players could peek into the future?

I'm gonna take an uneducated guess that though the simulation is in lockstep, the order of inputs from all players is not known ahead of time so you can't peek too far. Though maybe a cheat engine could simulate a few branches of possible inputs a few steps ahead and adjust inputs when it discovers split-second advantages?

Deterministic multiplayer has an assortment of cheating problems that weren't really a big deal in the early days of online multiplayer, but certainly are now, in the days of ranking systems and very competitive gaming.

The obvious one is that the client knows where everything is on the map, even when hidden by fog-of-war - so client-side hacks can reveal that.

A hacked client can easily desync the game too, or stall it and cause it to time out if the player is losing.

Re: 1500 Archers on a 28.8: Network Programming in Age of Empires and Beyond (2001)

#123

Post by maartet »

IntelMiner wrote: post #118
ies7 wrote: post #21

Earlier quoted context omitted.

We've 10/100mbps in 2001 and I think 1500 archers on 28.8k hayes is a great challenge no matter what the year.

Reminds me of the anecdote of John Carmack developing Quake in the early to mid 1990's He put out a comment effectively saying "I forgot not everyone has a T1 line. I'm going to order Dial-Up for real-world testing"

Ah, I remember playing Quake death match at night in the late '90s on a university connection, against scores of opponents on dialup. It usually ended with somebody shouting "Everyone, go after that LPB" (Low-ping b**d). Then finally there was some real challenge :)

Re: 1500 Archers on a 28.8: Network Programming in Age of Empires and Beyond (2001)

#124

Post by AshleysBrain »

What I find interesting about the lockstep approach described here is it seems a lot of modern RTS games still use the same approach, even though the bandwidth calculations have changed radically. When developing my own RTS game I was able to fairly straightforwardly get 1000 units in combat to live stream using about 50 KiB/s bandwidth, which is nothing these days: https://www.construct.net/en/blogs/ashleys-blog-2/rts-devlog...

So as much as this is a fascinating piece of history and an impressive technical solution to the constraints of the time, I think modern games ought to move past it.

Re: 1500 Archers on a 28.8: Network Programming in Age of Empires and Beyond (2001)

#125

Post by Emjayen »

reitzensteinm wrote: post #121
Emjayen wrote: post #119

Earlier quoted context omitted.

It is, in fact, inherent to this model. While there will be some tolerance threshold as to how far behind in the simulation a machine may fall, it still must be rather conservative (generally a few seconds), as elsewise the context (state-) sensitive inputs start frequently failing -- if I issue a command given at world-state time t , will it be meaningful/valid at state t2 ? The answer is where you get your threshol…

If it's not valid, just throw it out! I've built and licensed a time traveling variant of this model (GGPO style) and spent years with thousands of concurrent users playing my games. And they operated just as I describe. Company of Heroes is more of a traditional AoE style and will happily queue up unit orders for a minute or more while it attempts to reconnect or catch up.

Are these players interacting in any way? If they aren't then it could be more tolerable, but one player being more than several seconds behind others is going to lead to a rather undesirable experience, especially in the middle of a battle (and having most of their commands dropped due to being invalid equally so)

Re: 1500 Archers on a 28.8: Network Programming in Age of Empires and Beyond (2001)

#126

Post by Emjayen »

skocznymroczny wrote: post #106
lamacase wrote: post #33

> Cheating to reveal information locally was still possible, but these few leaks were relatively easy to secure in subsequent patches and revisions. I don't understand this. Running the whole simulation locally on both ends means that a modified client would have access to the whole game state, and I don't really see how you could patch that out. Anyone have any idea what they actually did? Try to detect modified cli…

One of the unofficial solutions used in Warcraft 3 was to spawn an illegal 3D model object in the corner of the map by a trigger as soon as the map begins, or during random spot checks during the map gameplay. The model would crash the game (and world editor, that's why we have to spawn it during runtime) when displayed, but it wouldn't get displayed when under fog of war, so you'd put it in a place that is impossibl…

Similarly, a common technique used within notably the DotA community (of which's map didn't have such a tripwire) was to analyze the replay for what were termed "fog clicks", since for whatever reason object selection is part of the command stream and those using maphack would often, intentionally or inadvertently, select objects otherwise under fog.

Re: 1500 Archers on a 28.8: Network Programming in Age of Empires and Beyond (2001)

#127

Post by qikInNdOutReply »

AshleysBrain wrote: post #124

What I find interesting about the lockstep approach described here is it seems a lot of modern RTS games still use the same approach, even though the bandwidth calculations have changed radically. When developing my own RTS game I was able to fairly straightforwardly get 1000 units in combat to live stream using about 50 KiB/s bandwidth, which is nothing these days: https://www.construct.net/en/blogs/ashleys-blog-2/r…

Did those units shoot? What happens when there is a few thousand projectiles in the air, fired by those 1000 units? What about map deformations? What about map wide physic simulations, like springs tsunami water sim or the lava flows of a volcano, changing directions?

Re: 1500 Archers on a 28.8: Network Programming in Age of Empires and Beyond (2001)

#129

Post by reitzensteinm »

Emjayen wrote: post #125
reitzensteinm wrote: post #121

Earlier quoted context omitted.

If it's not valid, just throw it out! I've built and licensed a time traveling variant of this model (GGPO style) and spent years with thousands of concurrent users playing my games. And they operated just as I describe. Company of Heroes is more of a traditional AoE style and will happily queue up unit orders for a minute or more while it attempts to reconnect or catch up.

Are these players interacting in any way? If they aren't then it could be more tolerable, but one player being more than several seconds behind others is going to lead to a rather undesirable experience, especially in the middle of a battle (and having most of their commands dropped due to being invalid equally so)

Giving the undesirable experience to one player is strictly superior to giving it to all of them.

There just aren't many modern multiplayer games where slow players can negatively impact the experience of others, and that's because the industry has learned how terrible the experience is.

And that's for players playing in good faith on bad connections - abuse by inducing latency was a big thing in the past. Think a player that runs out the clock when they're a move away from being checkmated.

Basically the only time you'd ever want to operate the system to pause if a player fell behind is during a tournament, where fairness is more important than player experience and they know that going in. And even that, IMO, is questionable.

Re: 1500 Archers on a 28.8: Network Programming in Age of Empires and Beyond (2001)

#130

Post by Emjayen »

IntelMiner wrote: post #115
Emjayen wrote: post #100

As someone who fixes up old games in my spare time, and Age of Empires II being one of them, I'll provide a bit of trivia about the game's internals: - The AI system is not part of the deterministic simulation. This was surprising to me, and after contacting one of the original programmers it was explained that it was due to a desynchronization bug that the "AI and network programmers weren't able to fix it in time".…

Absolute left field question. Have you touched the other RTS contemporary of the time, Red Alert 2 in any detail? I've been told the source code for it leaked some long time ago and has floated around for the past two decades or so. While most people contend that EA had lost the source code to the Command & Conquer series games many years ago when the studio was closed down and assets were shipped to "DICE" in Stockh…

RTS-wise it's just been Blizzard games otherwise; Starcraft and Warcraft III, the latter of which I did the most work with, mainly multiplayer optimizations and writing a server implementation.

However, I have been entertaining the idea of supporting other deterministic (RTS-) games, adapting them the same way --rearchitecting the multiplayer system/code-- as I have done for Age of Empires II, providing a unified platform for these games. The first candidate that came to mind was the Red Alert series.

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