Category:AI War 2: All About Multiplayer

Initial Caveats And Related Resources

• Please note that multiplayer is currently in alpha status. If you have not read about that, or the current status of where it is is, please see this page.

• If you are testing during alpha, we have a variety of questions for you that we would definitely appreciate you taking a look at.

• If you want to know what the known outstanding issues are, a pretty good summary of that is here. In some cases, particularly for features we might add, that can be rather vague, so more data is on our our mantis bugtracker.

Reporting Bugs Or Suggestions

• Any bugs or requests should go to our mantis bugtracker
  • If you need to submit log files, those can generally be found under your PlayerData folder in the folder your game is installed in. The most relevant one is called ArcenDebugLog.txt. You can send us the whole thing, or just strip out relevant parts.
  • In rare cases, mainly if your entire game crashes (that almost never happens), we will need your unity player log. That gets overwritten the next time you run the game after a crash, unlike the other log. These can be found here:
    • Windows: C:\Users\username\AppData\LocalLow\Arcen Games, LLC\AIWar2\Player.log
    • macOS: ~/Library/Logs/Arcen Games, LLC/AIWar2/Player.log
    • Linux: ~/.config/unity3d/Arcen Games, LLC/AIWar2/Player.log

• If you have been generating logging information that is networking-specific, then that will also likely be in the PlayerData folder, in some cases in subfolders.
  • Generally with those sorts of logs, we need the equivalent log from the host and at least one client (whichever client had the problem).
  • But, also, we really don't expect you to be generating these sorts of logs for us typically, so these really are going above and beyond if you are sending those in.

• In other cases, if you suspect something is wrong, then opening the escape menu during the game and taking a screenshot of the stats there to send to us is welcome.

• Relating to multiplayer performance problem reports:
  • Knowing how long (in actual realtime, not gametime) you were playing in a given session to go along with the amount of data transmitted and performance you were seeing is useful.
  • Knowing rough distances between the players (intercontinental, same country, same metro area, or same building is also useful if you're having performance-related problems.
  • Similarly, knowing the general strength of the internet connections in question is useful if it's a performance problem, as well as which networking framework (Steam, GOG, or LiteNetLib) was used is also helpful. If one or more of you is running this over a VPN, that's also important for us to know.

Multiplayer, At A Glance

This game is a client-server model, with one host, and any number of clients who are connected to that host. There are several networking frameworks available to use, but the host and clients must all be using the same one.

About The Host

• If the host severs the connection, then the game is halted for everyone else. A new host is not automatically chosen.
• Only the host can save the game, at present. Even with our improvements to multiplayer sync, clients are too likely to have slightly-garbled versions of the game.
• The host must start up the game first, either in the lobby, or by loading an existing save or quick start. The clients are then able to connect, based on whatever the rules are of the networking framework everyone is using.
• The host should have the most powerful CPU, as it runs a lot of background AI commands that clients do not need to run.
• The host should also have the most robust network, as they have to send approximately 2xn the data that a client does, where n is the number of clients.
  • So in a two player game, the host is probably sending and receiving roughly 4x as much data as the sole client.
  • In a three player game, the host is sending and receiving roughly 6x as much data as either of the two clients.
  • A spectator client adds roughly the same amount of bandwidth requirements as a regular player.

About Clients

• Each client connects to a host, and passes the name of their current Player Profile (as configured in AI War 2 itself).
• Clients (and for that matter the host) are linked back to their prior faction based on the player profile's name, so changing that midway through a campaign with friends is not a great idea.
• Clients are in general in a state of slightly-wrong-sync with the host, though the game does its best to keep everything consistent.
  • There's a rolling sync process that sweeps through and corrects inconsistencies within 3-4 seconds on each client, and so in cases of high desync clients may see things jump to correct themselves to match the host.
  • This is not something the host will see, as the host is treated as the "central correct record" for everything.
• It's worth noting that if a client is lagging behind, it will slow the host and other clients to wait for them. BUT if a client is disconnected entirely, then the game will continue without them (though any other player can pause it; they can then save, stop, or continue).
  • It's also worth noting that the host and the other clients do not have to disconnect or restart anything in order for the missing client to connect back. When the missing player returns, there is usually just a 1-5 second pause (depending on the size of the savegame) while the client gets caught back up to speed. But you don't even have to explicitly pause the game.
  • If sync is ever atrociously off on one client, that client can always use this to their advantage to disconnect and reconnect and have perfect sync again (although sync being that bad off is not supposed to ever happen).

Bandwidth/CPU Requirements And Player Counts

• There is a built-in limit of 254 clients connecting to a single host, but for practical purposes there's really not going to be remotely that many players supported.
• How many clients are actually supported is a matter of bandwidth between them and the host, as well as CPU processing power for the resulting game.
  • If there are 40 clients all sharing one faction, then this is far less of a load than 40 clients all with their own starting planet and unique faction. It's several orders of magnitude less CPU processing, to the point where the former might be barely possible on a nice LAN, but the latter is not possible with current hardware.

• As the years pass and multi-core processors become stronger and also add more cores, AI War 2 will naturally spread out to use those capabilities with no code changes required. It would probably take 16 or so cores before you stop seeing any tangible benefit.

• At the moment, with one client and one host in a fairly average starting galaxy with one AI and two player factions, the bandwidth requirements are less than 100KB per second on the host (in many cases closer to 10KB per second). The client ranges from half to a quarter of that amount, depending on what stage of the game we're talking about.
  • With just two players, far more important than the speed of the connection is the reliability of it. Lots of dropped packets and resends will cause delays even if the actual connection is plenty robust.
  • With two clients and one host (aka 3 players), the client requirements stay the same, but the host bandwidth requirements go up to something in the 200KB range.
  • It's actually expected that, for most practical cases with more than 10 total players, the CPU load of preparing all the extra network messages will probably cause more slowdown than the actual sending of the messages. This is something that we have worked around as much as we can, but also not something that more CPU cores will help given the linear nature of the data we are sending.

• The bottom line is that, in most situations, you should have a fine time as long as you have a 10 or fewer players, but we'd be interested in hearing what sort of experiences you have.
  • For practical purposes, the game itself will probably bog down with more than 4-6 human factions on current hardware.

Which Networking Framework To Use?

The game supports three networking frameworks at present, although more could be added in by ourselves or modders.

What Is A Network Framework?

A networking framework is responsible for transmitting data between players, and for getting players connected in the first place, but it is completely unaware of what data is being transmitted.

Conversely, the game itself is responsible for preparing and handing off all the actual messages it wants to orchestrate between players, and it has no idea where those messages go (at a low technical level) or how they get from the client to different hosts.

Some networking frameworks are more efficient than others in terms of how they use CPU and RAM on the client and host, and also in terms of how they use your network card and available bandwidth. They also can differ in what sort of networks they use, and so again can have a big impact from that area alone.

Steam

In this networking framework, you don't have to worry about IP addresses at all. As long as all of the clients are Steam friends with the host, you're good to go. Firewalls and network configurations don't matter much.

The host starts a game while logged into Steam, but they do not have to be in Online status on the Steam Friends section. Even someone who appears Offline in Steam Friends can be a host or client.

The clients will see a list of their Steam friends, sorted first by those who are currently online and playing AI War 2, and then by those who are online, and then those who (at least seem to be) offline. You can click connect next to any of the friends and try to connect to their game, even if they appear to be offline. It won't hurt their machine or yours, and if they have a game open even while Steam Friends is set to offline, you can connect to them. Please do only connect when invited, though!

It's worth noting that all of the network traffic is routed through Valves relay servers at all times. This will typically give you better performance than the general Internet backbone, according to Valve. You CAN also use this while on the same LAN as other players, but your performance and ping will be as if you were on different networks in the same city. Aka, far worse than if you were on the LAN together, but still plenty great for most purposes.

GOG Galaxy

In this networking framework, you also don't have to worry about IP addresses. As long as all of the clients are GOG friends with the host, you're good to go. Here again, firewalls and network configurations don't matter much.

The clients will see a list of their GOG Galaxy friends, sorted first by those who are currently online and have an active AI War 2 multiplayer session open. You will then see the others who are offline, or in game, etc. The various statuses don't really matter except for the ones that show up as purple, who have a game actively open at the moment. You won't see a connect button except for players in that status, so be sure to refresh the list of friends frequently if one of them just opened a game and you want to connect.

We're not sure exactly how the network traffic is routed. There are relay servers involved if a direct connection can't be made, but we're not sure if a direct connection is used in cases where it can be. Performance seems great in general, but definitely is relay-based if you are on the same LAN.

LiteNetLib

If you're on the same LAN as the other players, then this is a no-brainer choice. If you're on different networks connected to the Internet, then it's your choice; to use this in that situation would probably require port forwarding on your routers, and that's something you can easily look up for multiplayer games in general if you want to go that route.

The game's network tab of the settings menu shows you your public internet IP address, as well as your local IPv4 and IPV6 addresses. You can also configure what port the game runs on (it is using UDP). Only the host would need to set up port forwarding for that port if you are playing across the Internet.

The host would need to give their public IP address (for internet play) or their local IP address (for LAN play) to all of the intended clients, and they then type that into the connection textbox and connect to the host after the host has started or loaded a savegame/quickstart or the lobby.

If you are on a VPN network together, then it works much like a LAN does, but whether or not your IP address for the VPN's virtual network adapter will show up in the game interface is dependent on the VPN service itself. If not, then most VPN services prominently show both your virtual IP address as well as the virtual IP addresses of any other folks in the same session with you.

VPN services usually try to forge a direct connection if they can (which is almost as fast as the port forwarding route, but not quite because of encryption), but fall back on a relay server network of their own if that is not possible. The speed of these relay networks varies hugely depending on the VPN service. Some of them are extremely fast and suitable for gaming, others are direly bad.

So What Should I Use?

• Are you playing the Steam version across the Internet? Use the Steam network framework. It's simple and really fast.
• Are you playing the GOG Galaxy version across the Internet? Use the GOG Galaxy network framework. It's also simple and quite fast.
• Are you playing on a LAN? Consider using LiteNetLib, as it's the most direct and will be the fastest by far. If you have trouble, you can fall back to Steam or GOG.
• Do you feel like avoiding Steam or GOG Galaxy, and you're an expert with your router? Use LiteNetLib with port forwarding for maximum speed.
• Do you feel like avoiding Steam or GOG Galaxy, and you're not a networking wizard? Use LiteNetLib with a VPN service like Hamachi or similar. There are many available.

How Do Expansions (DLC) and Mods Affect Multiplayer?

How Can Players Participate In A Multiplayer Session?

What Multiplayer-Specific Features Exist?

What Do I Need To Know About Balance In Multiplayer?