UniKnowledge entry: Unity Networking the Zero to Hero guide

Edit: A greatly improved version of this tutorial project is now available on the asset store.




Download the pdf here: http://www.M2H.nl/files/M2H_Networking_Tutorial.pdf (+/- 700kb)
And the project folder: http://www.M2H.nl/files/M2H_Networking_Tutorial.zip (+/- 28mb)


Original post

I'm writing a unity networking tutorial as entry for the UniKnowledge contest.

This networking tutorial is meant as the one and only guide you need from start to end. It covers the very basics and ends with a game example. I think it's most important to have allnetworking issues covered at least a bit, the next priority is the depth of the tutorial.

The tutorials pdf will be combined with a unity project featuring several independent examples.

I'd like to hear what you want to learn about Unity networking so I can make sure I've got it all covered.

 

I look forward to reading this tutorial.
I am new to unity and so far this is where I am haveing the most issues. Havent found any detailed docs on networking yet for unity.

Depending on how deep and detailed you are going with this tutorial I would like to see some of the following information(Since you asked for some ideas) :wink: :

1. Information on setting up a lobby system.
2. Multiplayer FPS setup

Will add more once I see an area I may be haveing an issue and other members. I am still digging around docs and forums trying to learn how to use Unity and such so that I dont post some "Newb" questions that are usualy already answered over and over. :wink:

 

That's exactly why I've chosen this topic, and why I'm aiming this tutorial to require no networking knowledge.

Thanks, both will be covered in independent example scenes so you know where to look for the workings&code.

 

Cool!

My top 3 networking issues:

* Where can I find / how can I host a reliable master server?
* What is the best way to do interpolation and extrapolation for fast moving players, and how often should their states be synced?
* How do you troubleshoot when clients in your games occasionally stop syncing their networkviews (even though they can still send and receive RPC calls just fine)?

 

Very much looking forward to this. I tried a small FPS myself and it never worked out due to networking difficulties.

 

SamK

This has been finished

Robur

I'll briefly mention 1. And to answer you right away: You could host one yourself on a dedicated windows/linux/mac machine (e.g. rent one at leaseweb.com). Furthermore dimerocker is hosting their own masterserver and sharing it with the community.

2. I'll answer this one right away too: This really depends on the speed and scale indeed. It sounds dull but you should update as often it is necessary; at one point you can't properly extrapolate any more, that's when you need more updates.

3. I'll need more information about this one. In my document I do treat all known networking bugs and limitations we've got, but I'm not sure what you mean here. Do you mean this bug: http://forum.unity3d.com/viewtopic.php?p=77193 ? If not; did you make sure the player runs in the background? If you did..then hm..THe only difference between RPC and observing is that observed bits can be limited by networkview.scope, whereas (sadly) this doesn't apply to RPC.

Great, working on this very last example today!

 

Hey Leepo!
I'm currently writing a networking tutorial, though, it is heavilt based on the Project Darkstar server written in Java. It is mainly aimed at creating a "Multyplayer Game" based on a remote server where the game is hosted.

I just wanted to wish you good luck and... just to know, you are using Unity's built in networking right?

Philip

 

Hey Philip,

Yea I'm using the built in networking, so we're not in each others ways :wink:. While the unity networking works great (and is very easy) for smaller (web)games, I'm looking forward to your Darkstar tutorial since it's great for the more serious networking setups. I might actually need to "go darkstar" soon myself, but I'll wait for your tutorial.

I've secretly been following your blog already.
Good luck to you too!

 

Leepo;

Thanks!

1: I am hosting my own master server right now, and I have also extensively tested Unity's main master server and the beta one that Larus set up and Unity is hosting. Bottom line - they are all so unreliable for me that my community has dropped over the last several months from around 70 users online at any given time to around 20. I get complaints all the time that people can't see any games to play in (and a diagnostic message that I trigger in OnFailedToConnectToMasterServer() is present in all these cases). Interestingly enough, users report that this occurs much more often in webplayer games than in standalone games. Larus has confirmed to me that this is a known issue in the latest master server beta, and has created some special diagnostic builds for me to do testing with - but so far I have received nothing but headaches for my trouble. If anyone is having success running a moderate volume master server, please tell me what you are doing! I recall in another post your mention that you were restarting Wooglie's master server every hour - did this help, and was it because you were experiencing problems similar to what I am describing? Thanks for letting me know about DimeRocker's setup - I will definitely give that a try.

2: Is there any mathematical / rule of thumb way to determine how often is necessary? Not a big issue, but I am currently syncing 20 times per second after reading http://developer.valvesoftware.com/wiki/Source_Multiplayer_Networking.

3: It is definitely something other than the issues you mentioned. Like I said, RPCs go through just fine (the player can still use the messaging console, fire lasers, etc), but their vehicle's OnSynchronizeNetworkView just seems to stop getting called. I finally gave up on trying to solve this issue through conventional debugging, and I am nearly finished rewriting my game's networking logic to never use buffered RPCs, and to always use as few networkviews as possible. The "not responding" issue seems to be decreasing in frequency as I continue to simplify my networking, so perhaps everything will just work once I am complete. If not, I will be in a much better position to isolate the fault anyway...

 

We were restarting the server because it kept losing the connection between the masterserver and the facilitator. Sometimes one of these would just crash without leaving any error message in the log. The masterserver seems to work nicely now though (check out crashdrive on Wooglie, a constant 100+ rooms). I'd like to improve connection problems by using a proxy, but have not yet figured out what proxy server I need to run (see other topic). However, using dimerocker should probably solve it for you if RD keeps their server running.

20 times a second is probably not required when you add more prediction code. However; in your game I don't think the bandwidth really hurt either. I'm not aware of any mathematical calculations to decide the right update rate, I guess you could come up with your own by using scale, and max. random movement distance. Personally I'd just play around with it and try to get the update rate as low as possible without it having any visual effect.

Very odd. This must be a unity bug, unless you use networkview.setscope (since that's the only logical reason I can come up with for why RPC's do work, but the serialisation does not). I have never experienced this bug myself though (In Crashdrive, Crate mania, Verdun online, Surrounded by Death). I'll keep an eye out for this bug now tough.

 

Will this tutorial be aimed mostly at web player games or standalone games or both?
I am mainly looking into the standalone multiplayer games at the moment and will later look into the web player games once I get more familiar with Unity. :wink:

 

Both, for multiplayer there is no difference. You can even have the webplayers play against/with the standalone players right away.

In fact, while learning unity it doesn't matter if you "learn webplayer" or standalone games first. The whole coding part has no differences.

 

Awsome thank you.
I was not sure if there was much of a difference between the 2 or not.

 

I hate to say this - but after running off dimerocker's master server for the last several days, they seem to be scarcely any more reliable than my hosted beta server was.

When running in the Unity editor, around 95% of master server requests go through.

When running inside a web browser (tested mainly with FireFox 3.5.2), around 70 % of requests work, and the rest result in a masterserverconnectionfailure.

In other words, my game is basically unusable.

I just played with Crashdrive a bit, and your masterserver seems to be working great! I sure wish I know what the difference was - it's incredible that something this seemingly trivial could pose such issues.

Most interesting of all however, was that I could only connect to around half of all the servers listed in Crashdrive - and of those, I was only able to find one server where other players were actually moving on my screen. In the rest of the servers, I could message everyone fine - but their vehicle's positions were not updating. Several players I talked to stated that this happened "all the time" - and that they didn't know of any workarounds for it. It looks like Crashdrive is suffering from the same mysterious issue I mentioned above as afflicting Mars Explorer

Are there any multiplayer Unity games that actually work? It's almost like there is a major flaw deep in Unity's networking core. Trying not to get discouraged here...

 

Yea, I got a list of (seriously easy to implement) additional features and bugfixes that would greatly improved the unity networking. But I'm afraid we're not getting any of it in 2.6 .

I did indeed notice the Crashdrive cars being stuck, but just haven't looked into it yet. I will do so soon, as it'll be handy to document this in my tutorial as well (as confirmed bug, or with a workaround).

Now wrapping up the last example (FPS game) for the tutorial first.

About the master server; I re-register the games every 2 minutes and have a cron set to restart the masterserver&connection tester applications every 2 hours. I should have no other differences except for load/server configuration perhaps.

 

I know of no current work around for this issue, I know it exists and what is causing it, have posted about it in other threads based on internal Unity engine, it has to do mainly with lost connectivity or a ghost as it were, not all packets are arriving reliably which is odd, I even have a test project in another thread around here showing the loss of the information but another user pointed out that although my referenced object looses connection, a direct connection call to the main object kept the information. The problem seems to sit in referenced object information.

Everyone codes their network project differently, so the problem could just be in the individuals code base. You could create a bug report about it, they do eventually get around to looking at every single bug report that comes into the queue, but it might be a while before the bug gets looked into. As far as I am aware, this latency problem has existed since 2.1, but again, that is just me. Others have projects that they say that they have never had any connection state issues which is what this is, the state of the objects during the open connection is getting reset and the object itself looses the network view information.

They are probably researching this problem, but not for sure, you would have to write support to find out if they know about the problem or any solutions to it.

 

You didn't say you knew any workarounds so I assume you don't. Might (regularly) resetting the allocated viewid's/networkviews work?

It only applies to observed networkview messages (also unreliable messages?)

 

Fascinating Zumwalt!

The more you can share about this, the better.
I had the exact same question as Leepo...


Leepo:

I'll try restarting my master server with a cron job, but I just don't see how it could help - this occurs randomly, then it fixes itself. Especially with the way that this issue is much more apparent in webplayers - it almost seems like a client side issue
Also, what is the best example you know of that illustrates properly functioning network position sync and interpolation in Unity? Even while syncing 20 times per second, my players jitter pretty significantly.

It would be great to hear either from some one who has succeeded in publishing a Unity game with smooth, bug free networking - or from Unity, acknowledging that there are major problems and that they will be fixed soon. The only Unity game I could think of that had decent networking was Paradise Paintball - then I remembered that they are using Proton... Such is life

 

As for a solid unity networking example; We're working on Verdun Online (http://m2h.nl/#Verdun Online). In our own tests so far the networking there works great; movement is smooth. We only had to use one fix for a unity networking bug (the instantiate error: http://forum.unity3d.com/viewtopic.php?p=77193).

But in Verdun we did not yet experience the bug you and Zumwalt described..so that might kill us. But then again, if I find it there I'll try a few hacks to get rid of it like re-adding networkviews and reassigning the viewids as soon as is the bug is detected.

Changing your update rate any higher than 20 probably won't help much. After that number I think you'll need to improve your prediction to cope with lag. Did you also already enable interpolation on your rigidbodies?

An a different note: If you like I can send you over my networking tutorial soon. It should cover the whole networking part you're already familiar with, but also lists tips and known bugs (with workarounds). I'd like some feedback about my tutorial before the official launch.

 

Yep, the instantiation ghosting thing bit me too

I would be glad to preview your tutorial. I am deep in the Whirld project - and preparing Mars Explorer 2.0 for UA2009 - but networking will definitely be a major part of the latter undertaking, so I might as well start battling it sooner as later.

I'll play with my interpolation code next time I get a chance - there's a chance I missed something and it isn't even working right. Definitely worth looking into again.

 

I would definitely like to see a way one could create there own username password, which this information is sent to the owner of the game, and people can log on and play.

I know nothing about networking, so if anything I stated above doesn't make sense, or makes me sound like a noob, you know why.

I'm really looking forward to the tutorial, though.

 

1. Simple, iterative steps

Working through the current networking sample, it took a lot of effort to separate all the bits out for a specific set of functionality.

I want to know what the minimum amount of code is that is required to address a certain set of functionality.

Then after I know the basics I can get properly bogged down in all the complex issues.

 

That's exactly what I aimed for, I had the same problem: The unity networking tutorial is too messy; way too much code, you don't know where to look.

My tutorial consists of several independent scenes, each with their own subject: A scene with only connecting/disconnecting, RPC, Observing(Serialisation), etc.

 

I have been working with the internal networking (outside of my own RakNet solution) for a while now trying to track down exactly what causes this and where the fault lies, whether it is a queueing issue, a network interrupt issue, or even just an object reference issue, all this based on my initial findings as to object instansiation to network view ID loss.

From what I have observed so far, this appears to be some sort of object reference issue. If you create a reference to a game object and associate a network view with that game object reference, this looses the view connection either immediately (within a few game loops) or over time.

I built up the network sample and deployed it to a few hosted network servers, one being a Linux CENTOS 5 server and one being a Windows 2003 standard server, both dual processor quad core machines, plenty of power house. I have tested for 2 weeks straight on two different itterations, one itteration was the authoritative design and then on the windows 2003, I setup a game as the server on the machine that same machine, so the server is both the game server and the master server.

Loss of network view ID is happening not by the master server itself, but within the internal client/server build inside the Unity core code. The master server is just an announcer, not doing much else at the moment. Somehow the client build is resetting the network view ID internally (sorry but I do not have access to the internal Unity code and I can't afford to buy a license to give me access).

This is beyond the scope of user based code and is essentially a bug. As since Unity gets over 500 bug reports a day and goes through them and prioritizes them, the likely hood that this will get fixed by 2.6 is low, it is going to require someones full attention and they have to identify the reason why the id is reset to null (that is the end result, the view id is nullified, not even equal to any value), on the proceding game loop, this null is then re-instansiated to 0, so it doesn't match any synched ID with anyone else and the object is just simply lost.

I am almost finished with a new sandbox that includes the deathcar from one of the user posted unity packages on the forums, when I am done, I will likely post a link to a download for the sandbox network game which will allow for additional testing. The server has ran with the latest beta network master server code now for a full week un-interupted, 4 clients attached 7x24 with intermittened client drops, and the only thing I see on the master server console is

"-INFO- Removing Rows for IP ...."
But the player machine didn't disconnect, didn't loose internet, didn't have frame delay or network delays of any kind, just poof. So this suggests that the problem is simply in the Client code portion of the network code internal in Unity. (again, sorry, beyond my financial scope of software ownership)

The player that was dropped, can simply reconnect and get a new network view ID and play on.

I want a more intensive test though, so as I said, the new sandbox will include the deathcar, with hopefully the turret working going to see about throwing in the remote turrets from the fps demo and if possible, also the bots. It is a flat play field with a wall surrounding it, not much of a goal, just kill or be killed and can reset to home position after death. With all this going on, hopefully the issue will show sooner than just driving around for a few days.

Hopefully in this zero to hero thing, you will have a way to code around this problem.

 

Hey, first. Thank you for working on this. I am actualy not a Unity Developer, just a 3D artist. But I am working on a small map where you run around and fight other people online. Problem is that I know nothing about networking and what I know about Unity I learned from this awesome tutorial on Learn Me Silly website, They covered a lot in a video tutorial that was super easy to follow. If you can manage to pull of this tutorial and make it as easy to follow as the Unity tutorials on Learn me silly. That would be awesome!

I got a lot of stuff working but as far as putting a second player into my map from a different computer, I dont even know where to start. I have tried to look it up today but everything is so complicated, the closest I got was with a program called Smartfox? I had no idea what was doing what but tried to follow directions, how ever it dint work and because I dint know what anything did, I could not figure out how to fix it.

Anyway, very much looking forward to your tutorial.

 

I've just finished the tutorial, I only need to refine/improve the text here and there. To improve this tutorial I need some people who belong to the target group to actually use it (and proofread the tutorial).

Are there any volunteers that want to learn about the unity networking and help refine the tutorial at the same time? Please reply here or PM me and I'll send you the download link to the PDF file and the unity project.

 

I would love to test it out. I have been working day and night on this project and that is the biggest missing peace I have. I will go thru it step by step and send you feed back, man, what perfect timing.

 

I would also like to help. Sent you a pm with email address.

 

Thanks! You and all the others who contacted me have received a PM/email with the two download links.

 

still can apply to refine it? or is one day after your post too late?

 

Sure, I've sent you a PM.

 

Ooh! I want in! I've been up to my head in networking, trying to get it right. I learned what i know so far from the little resources that are out there, including the networking example. What really bothered me is that even though the example gives you a functional project, it doesn't really explain anything or guide you through the interesting bits. So i thought about writing a tutorial like this too once i felt i would know enough. Since that apparently hasn't happened yet, i'm very interested in reading your go at it

Also, the thing i haven't figured out yet is how to do client side prediction in Unity. It seems to me that you need more control over the engine than Unity gives you, since you would kind of need to be able to rewind the whole scene and play out some simulation steps with updated information when server updates arrive. Am i right about this? And does your tutorial cover a solution or a workaround? In any case, i'd like to contribute to the tutorial while my own trials and tribulations are still relatively fresh in memory.

 

Thanks, I've send you a PM with the doc&project folder links.

No you don't need more control, you can already do this in unity. The networking examples even contains an example. You can delay the multiplayer game by e.g. 100ms and therefore always know what's coming next, and use that to battle lag. Furthermore prediction is always possible by taking the last few actions into account.

My tutorial briefly discusses prediction too, after you've read it you can have another look at the unity networking example (the interpolatednetworkXX script).

 

Bump; released the tutorial to the public. Suggestions and feedback is still welcome.

 

I have not had a chance to realy go through the tut. but just browseing it looks great.

Thanks for makeing this for the community. I am positive it will help me out. :wink:

 

Leepo;

You might want to include the information that is being compiled @ this thread - it has been invaluable to me when developing advanced interpolation algorithms and tuning for minimum lag.

 

This has been my exact same issue also and has made networking nothing but a mere dream for me... i am so glad I found this thread! Wow! I am going to enjoy reading this!!!

But to jump the gun, I want to quickly ask something. I think the answer is obvious but as I have never done any networking code I think I will just come right out and ask.

An idea I have had since 1998 is to have an arena (boxing, baseball, whatever) with a number of players participating in the event and then other people could log in and become spectators. Imagine a game like yu-gi-oh where you win the opponents cards so if you loose, you loose big. A great way to find out if you want to challenge someone is by sitting in the arena and watching him/her battle someone else.

Now, if 1000 people want to join an active game, but they only SEE the game being played, will they still require the same amount of network traffic as the people playing the game? What about the people playing the game, can I show them the actual amount of people in the stadium or will that kill the game? What about if I load generic character models on the client side to represent the audience and only send through the audience member's name and transform? Is that viable? What I would like to do, ideally, is to have the audience be able to move around the stadium and speak to other people.

How doable is something like this? Should I set an audience limit of like 32 or so and that is it? Can I do this for in the thousands or is this completely unpractical?

 

From a network perspective you would want to segregate the viewers from the players, so viewers don't add lag to the player experience.

You would have to stream exactly the same data, but for the viewer it doesn't matter if there's a bit of lag, even a couple of seconds wouldn't really matter that much.

What you could probably do is create only one "viewing" server that would be a client of the "authorative" game server. This means that the server actually overseeing the game only needs to broadcast the status to one additional client.

Then you could have viewer only clients connect to the viewing server, and that could almost be a whole independent game on its own.

It would be pretty complicated, and I would encourage you to do a more straightforward networking game first, just to get a hang of unity networking. Then you can decide if you want to use unity's internal networking, or rather go for a 3rd party tool

 

the logic seems clean. I was worried that the more spectators join the match, the more lag there is going to be between the players and the spectators would then inadvertadly cause glitches in the battle and spoil the fight...

Imagine doing a baseball game. Each player is a live player and each one of the parents and family and friends gather on their own PCs to watch this historical first-ever online baseball match between the two great rival schools... and because the entire school is there, the lag causes the ball to skip through the bat or the bat to not swing at all... eww...

But sending the data to another server that does this processing is an idea I have not yet thought of. Thanks for the tip. Also, I agree that I will have to start small. I was just curious about this because I have had this idea for a very long time now, just had no idea IF and IF then HOW...

So many thanks

 

thank you leepo for the tutorial. very helpful 5 star source.

 

Thank you very much for this guide!!

 

Thanks Leepo, its a great tutorial.

Hope that zumwalt manages to get the Raknet stuff working and you can do a tutorial on that.

tomcat

 

thanks very much for your tutorial Leepo.
God Bless you.

 

I'm downloading your tutorial now. After I get the chance to read it all the way through (give me about a week or so), I'll post back with comments and feedback. Sounds like you've provided an awesome service to the community. +1 for you!

 

Please help me ,..all master

there is a basic tutorial for car multiplayer in UNITY?
give me the link please..


tnks for advance

 

Thanks for the kind words, I hope this tutorial really gives you a headstart.

Raje: If you know how to make a racing game and you know how to make a multiplayer game, then a multiplayer racing game should be simple.
Check out the Unity networking examples for a simple "multiplayer car" example.

 

Leepo , tnks for ur kind guide for us,..and ur tutorial are very usefull ....tnks a lot

 

UniKnowledge voting has started here:
http://forum.unity3d.com/viewtopic.php?p=214782

(You can find the other entries at http://forum.unity3d.com/viewtopic.php?t=28307&postdays=0&postorder=asc&start=110.)

 

I've made a few small adjustments in the document for 2.6. It's a pity I can't remove any of the networking bugs/missing features.

 

We hear you loud and clear on that one.

Unity! Pleeeease give the networking some love!