I am in the planning phase of a mobile multi-player real time game and I am considering what architecture to implement in order to keep track of state within a game lobby.
I have considered making the game either peer-to-peer where all devices within the same game lobby (4 players max) will emit their position to other players as the game progresses. I have also considered having the players connect to the server and the server keeping track of the game state and sends the state to every player.
If I do go this route and implement the server using node what are some considerations that I need to look at?
I have a prediction that scalability will be a major issue as the server has to keep track of the state of every game lobby that is nominally running at 60 fps. If I have 100 active lobbies I can foresee the issues that could arise. Will this be the case and should I look into a different networking architecture? or could I get significant capacity until the server reaches a maximum?
Depends highly on the kind of game.
The peer-to-peer solution is probably tricky and cheating would be pretty easy except you validate it on every client but since you want to run it on a mobile client that would slow down the game a lot.
It makes more sense to validate the data on a central server and just send out the validated data.
In general the FPS doesn't matter for the server at all.
Every client just emits user input to the server and not every frame
(button pressed - button released).
The server uses all this information and calculates what needs to happen and sends regular updates to the client.
Then the client renders everything like 200ms (really depending on the kind of game) in the past and "predicts" what the server will send in the next update to make it look smooth.
Just read this article, it explains it better than I ever could: https://developer.valvesoftware.com/wiki/Source_Multiplayer_Networking
But yeah, it will def take a lot more power than a normal website.
However, the single lobbies don't need to communicate with each other so you can super easy just use 3 servers in parallel.
You can expect Node to perform pretty well in comparison to most alternatives you have cause it handles concurrent connections very well. Just make sure you don't run CPU heavy things because that will pretty much kill Node (if you just receive status updates and use basic math to validate it and send it out again ->perfect choice).
Hope that helps
The biggest issue you will run into is Node is not built to handle application that are as latency sensitive as real time simulations.
HTTP is a bloated protocol, and it's text-based. It will not work for the type of games most people would consider multiplayer. It may work for games in which high latency is not an issue such as facebook games.
I am building a simple game with Node. I use socket.io for communication between devices.
I want the node server to handle all the game logic; collision detection, scores ect.
The Node (socket.io) server should then send some display infomation to clients; player position, score, map size ect.
The client should also be able to send navigation commands to the server, like up and down. It might also need collision detection to avoid that you try to step out of the map ect, there is no need for us to send the navigation data then.
My question is, are there any libarys that handle this kind of logic? I know there are some game libs out there for JS, but as far I can see they are for handling the logic and rendering, and are not made to be used on a Node server.
I have used Crafty for both rendering and logic before. I am thinking that I'll draw the game with Raphaël.
You could maybe try the SDK from GameClosure? My understanding is that it has a lot of that sort of stuff available, though I've not used it myself.
That said, the idea of just doing everything on the server is a little bit odd. The performance and responsiveness of your game is going to become very dependent on the player's connection to the server. There are other schemes that have been implemented for many years in multiplayer game servers, which is a kind of client-side calculation with the server ensuring that the clients are doing that calculation correctly. Is there a reason it all needs to be done server-side?
I found BonsaiJS.
It's a nice Ghapic Libary with an architecturally separated runner and renderer.
I'm implementing a game app based on cocos2d-x. In order to technically prevent cheating, one of the ideas to do is using HTTPS for all the client-server communication, which make it difficult to get the data format / game logic and send modified request to cheat. (I know "prevent" is actually impossible but for increasing the cost of making game cheating it's ok : ). My question is,
In Cocos2d-x, how to make HTTPS request? Possible?
In a more general case, technically what to do to reduce such game hacking? What strategy to hold?
For native cross platform C++ networking you may consider using Boost C++ libraries. Boost.Asio is the one used for networking.
Boost.Asio link:
http://www.boost.org/doc/libs/1_53_0/doc/html/boost_asio.html
Boost.Asio tutorials link: http://www.boost.org/doc/libs/1_53_0/doc/html/boost_asio/tutorial.html
Although not officially supported (only due to lack of regression testing on iOS and Android), Boost runs without any problems on iOS and Android (and probably other C++ based mobile platforms as well).
To prevent cheating you usually rely on an external source (which can be your game server) e.g. if your game relies on the time of day you may get the time form an external server. You may use encryption libraries for data transfer on the client and server side.
by using curl library you can make https connection.
if you want technically protect your game use you own strong encryption technique.
Thanks
Hi this is a problem we face all the time. If the cheating is limited to the cheater's instance the questions is academical and should be studied on your spare time.
On the other hand when your income is impacted or when the cheater's actions impact other players and degrade the game experience you should put some effort on testing the game state for inconsistencies, secure the client/server transactions and deal with cheating in very subtle ways to avoid completely deterring the cheaters' interest.
C++ https implementations are available with curl and boost.
Concerning the game data, the simplest way to test for inconsistencies are scores. You can add a few indicators to avoid polluting your leaderboards. You can add special checksums based on the score's components (time spent in game, number of power ups and score multipliers received...) if you can recalculate the score on the server and if inconsistencies are discovered you can deal with it.
Also you can grab instants of the game state and a few commands, encode that and replay the sequences on the server to check for inconsistencies. Deal with cheaters however you like.
When playing on a server let the server manage the gamestate and allow no client side game state changes that would impact players. Check for input consistency etc...
When using micro transactions each micro transaction should be verified with the vendors servers before being fully committed to the player's account.
Even if these papers 1, 2 from valve refer to fps games they should give you some pointers as to how to deal with state inconsistencies (introduced by communication delays). It should help in avoiding fake positives and ruining the experience for non cheaters.
After the Sony PSN debacle, I am trying to find examples of secure hardware tethering to a network. There are two use cases in particular:
1- computer downloads a piece of software that then uniquely and securely labels it to a cloud service
2- a hardware manufacturer uniquely labels a hardware device that then negotiates membership on the network.
Given the fact that the hardware device might have to change (revoke or service enhancements) it feels like #2 becomes #1.
The broad outline is this:
- connect to the service via HTTPS to protect against man in the middle
- device generates a GUID and presents it via HTTPS to service
- service records GUID against account
- on success, service 'enables' device
But how do you protect the GUID so that it cannot be stolen?
I just wanted to comment here:
Sony's PSN issues started with horrible practices with regards to their QA environment.
First, they defaulted to trusting anything that was sent to those servers using their developers toolkit. The reason they did this was that the dev kit used to cost upwards of $10k US and therefore they thought anyone who paid that amount would be on the up and up. However, when they radically lowered the price things changed externally and they didn't account for it.
The second issue with PSN was that the security between QA and live was, well, weak at best and easily circumvented. My understanding is that you could send commands to live using QA credentials. Because QA credentials were used, all chargeable actions were approved without money changing hands and the actions were applied to live accounts. When several people told Sony about this they did nothing.
A third issue was a reliance on hardware based encryption keys. Even hardware encryption keys installed on the devices can be figured out.
Point is, Sony dug their own grave on it so I wouldn't use anything they did as a template for how to do things. Heck, a lot of their websites were open to SQL injection which in today's day and age should get you fired.
Another example here is the iPhone. Each iPhone has a unique identifier that installed apps can grab and send back across the network; similar to a serial number. Some apps use this ID to try and tie a particular device to a person. However, it's trivial to create ID's and broadcast them, so this hasn't worked out so well for the partners. Also Apple does not expose a way to ensure a given ID (UUID) is valid to app producers.
A third example is mobile phone carriers. They use a particular ID baked into your SIM card to identify your account in order to know who to bill when a call is made. This ID is verified whenever the phone checks in with the network. However, we're dealing with radio signals and any device that can broadcast a correct ID can gain access. Point is, honest people think that only AT&T approved devices can get on an AT&T network. Reality is, anything can but they are going to bill the owner of the particular ID...
That said, any software you have running on a remote device that is not under your direct control is likely to be hacked. The popularity of the device will increase the likelihood of it happening sooner rather than later.
Where do we go from here?
On a basic level you associate an ID with an account in your service. PSN, Apple and others have done this. When an ID is broadcast, you need to verify that it exists AND that it's tied to an active account. If both pass then you have two options: either perform the action requested OR request additional verification.
For any actions that require money to be spent, do the additional verification (usually some form of username/password), capture the funds, then perform the action. Go one step further and every time a bad login is entered, send an email to the user on file. Further, automatically send a receipt. These are typically done so that your honest users can tell when something is going on.
Anything else just let through.
Bearing in mind, of course, that QA credentials should NOT work in your Live environment. Those systems should not be tied to each other under any condition and, quite frankly, should even live on separate hardware. In other words, QA and Live should NOT share a login database.
The thing here is that you shouldn't care about the device itself; just the account. You can't control the device as it's out of your hands; heck you can't even be sure it hasn't been physically tampered with. (XBox has been fighting this one with people adding resistors or burning out certain components to get past physical security features).
So, IMHO, do a bit to keep honest people honest but overall don't worry about it. Now, you should transfer everything via SSL or someother encrypted connection between the device and your cloud so that you don't leak ID's to anyone that wants to grab them. This will help protect those honest people.
Further, you shouldn't have a direct way to query whether an ID is valid or not from the outside. This will make it a bit more difficult for a hacker to find existing valid IDs and take over accounts. If you want to get fancy you could honey pot those and track the hackers down in order to sue them into oblivion, but that takes time and resources companies don't normally have. Also you could log all of the requests that contained bad IDs and use that to track hackers down.
Note that even after the device has been "enabled" I still suggest you have two levels of authentication. The first is for simple actions like downloading free content; the second kicks in anytime there is a fee associated. Again, we're trying to protect your honest subscribers.
For the dishonest ones you will have to apply some statistical analysis on the transactions coming across. Things like the transaction rate can help identify bots that are running and allow you to kill their IDs. There are others but they'll be unique to your application.
This was long winded. But my point is:
You can't secure the ID or anything else you pass out.
You can't ensure the requests are coming from your devices or your own approved devices.
You better take actions to keep QA and production separate for those building software for these devices using your services.
You better take actions to protect your normal honest users.
Trust NOTHING.
Due to the above you should evaluate your business model so that you don't care what device was used and instead focus on the individual accounts themselves; which you do have control over.
I am not sure I entirely understand the question, but I think you want some sort of device to hold on to a GUID assigned to it by a web service, and you don't want someone finding out what that GUID is, correct?
If so, there isn't a lot you can do. You have already mentioned one option... using HTTPS during the assigning of the ID. That is a good start, but remember that anyone who has physical access to the device can do a lot of things to look up this ID.
In short, it is impossible to completely hide. Someone can always reverse engineer it. There are folks out there reading data right out of memory with hardware.
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I'm sure that all of us have had to deal with telecommuters at some point in time, and I'm facing a situation now where my new project will have a "core" group of office workers and some off-site telecommuters. Not wanting to repeat past mistakes, I'd really like to know what ways people have tried in the past to effectively integrate telecommuters in an agile process, namely scrum.
My first fear is that the telecommuters will be the first ones to break the "daily scrum" routine. And, as human nature often goes, once that gets broken, it's hard to resume and get people back on track. Scrum recommends enforcing small, fun "penalties" for people missing or being late to the daily scrum, like donating a few bucks to a jar which would later be used to buy a case of beers for the end-project party or something. This is obviously something that would be difficult to enforce online.
The other big problem with telecommuters is the "out of sight, out of mind" problem. Aside from using webcams/skype/teleconferencing, what other tips do people have for keeping the team as closely knit as possible?
Also, what about dealing with telecommuters from different timezones? At the moment, we're lucky enough not to have this problem, but it's definitely a possibility at some point in the future. How have other teams dealt with this problem?
Instant messaging really helps with the "out of sight, out of mind" issue as their 'Status' (Available, busy, on the bog, etc) is visible to all. Also, by responding to messages they reinforce the idea that they're generally available.
I wouldn't worry about the Scrum meeting issue, joining a meeting via teleconf is often easier than attending in person.
Set the ground rules upfront. Don't be wishy-washy about them.
You've probably eliminated the "I got stuck in traffic" excuse for missing the meeting or whatever when they're working from home (or a satellite site) and so there's no reason to expect less out of them.
Take advantage of technology:
Use IM. We use it here and it is great for 'reaching out and touching' the guy four states away. Make it a requirement to be available via IM.
Use other tools to help break down the barriers. It'll depend on your situation.
If you're having the daily meeting, it should be clear to everyone that you're going to be asking the questions:
What did you accomplish since we
last met?
What are you going to be doing
today?
What's in the way that needs to be
moved?
Just because you can't see Matt in his cube doesn't give me a right to be lazy or unproductive and unresponsive. It's like dealing with my kids - let them know the rules and what is expected, then nobody can claim ignorance.
We have success using this tools:
Assembla for project management (source control, wiki, scrum tool)
Skype for voice communication
Google talk for im
We are team of 3 developers, in 6 time zones range.
I spent a year as the only remote guy on an Agile team. I called into a conference line for the daily scrum, as well as the planning/review meetings. I kept in contact during the day via IM/e-mail/phone.
I think it worked pretty well overall. The biggest constant drawback was not being able to see the physical whiteboard we used to track the scrum. We discussed moving to some sort of online tool to do this, but it never happened.
I was one timezone away, and I just considered it part of the telecommute tradeoff that I would work the hours that the rest of team kept.
As far as penalties for missing SCRUM - to a certain degree you should enforce this loosely, via the beer jar or whatever. But if someone is consistently missing/late required meetings, then their manager needs to address that.
The are a number of techniques that you can use - remember the purpose of colocation is to encourage collaboration and communication. A few things can help out.
If your team is all nearby - think about having core days of when everybody can come into the office. My current team allows working from home on Mondays and Fridays - and everybody comes in the office Tuesday through Thursday
For distributed teams, I have had good success with using Wikis instead of giant sheets of paper on the wall. The nice thing about wikis is that they encorage the team to edit the forms to meet the needs of the team as opposed to adapting to a more formal tool.
Another advantage of having a Wiki is each person can have their own page to share pictures about their vacations and hobbies - this makes remote people more real.
When you have a distributed team, I want to second the use of Instant Messaging that includes a status (Available, Away (grabbing a cub of coffee), Busy (in a meeting)) - these can include notes if people switch between working at home and at the office.
Webcams are inexpensive and valuable tool
Invest in a decent speaker phone (we like Polycom phones) for your group conference calls
Use tools like LiveMeeting to promote remote pair programming
A technique for doing stand ups over the phone is to have the person talking say the name of someone else in the group who has not gone yet - this keeps everyone paying attention.
For iteration (sprint) planning meetings - follow up with meeting minutes or a communication plan to make sure that everyone is on the same page. Not being colocated means a tad more documentation and intentionality on communicating.
Good luck
SCRUM and many other agile methods really do depend on physical proximity - it is hard to integrate telecommuters into any development process where integration happens frequently, but these particular processes are especially hostile to disembodied developers.
You will have to adapt the processes to the situation at hand. Video conferencing using webcams is actually very usable, and in fact yo might want to experiment with having their webcam on all the time in their cubicle/work area so people can just walk up and ask a question as they would with any other coworker.
But at the end of the day, you simply have to expect things to go differently for them - they aren't going to be able to fully participate in many processes if you are an agile shop.
-Adam
Make sure they attend the daily standup via webcam; as you said that's the first mis-step down a slippery slope. We try to have all meetings done with a RoundTable as well which really helps.
I've been doing this for two months (working in Canada with the core team in Dublin) and so far everything has been going really well.
See Scott Hanselman's writeup on his first year working remotely at Microsoft - definitely some good tips there. One Year Later.
Instead of a beer jar, the privilege of telecommuting itself could be part of the bargain for participation when required. If the team is not responsible enough to telecommute properly than they probably shouldn't be. More fun penalties for occasional tardiness could be to use a funny avatar to represent the person that is missing from the meeting.
Other methods of keeping people closely knit is using collaboration tools such as Wikis and project tracking tools such as Basecamp or FogBugz.
For differing timezones, early meetings will need to occur based on the furthest west time zone, unless one is on the opposite side of the world, which is a bigger problem. Then it will probably be based on who is in charge.
We have been able to manage daily scrums in our environment even with distributed teams over the phone.
It helps to use software such as Rally and Basecamp to manage the process.
One place I worked used Asterisk instead of a normal phone system. It worked well because when you are working from home, you simply log on, people can call your direct line number, outsiders don't need to know. Even though phone call cost are relativity trivial these days, having a 'always on' connection encourages more communication. The sound quality is better too.
For telecommuters/distributed teams, I recommend getting a decent phone - most desk phones lose the ability for folks on the other end to hear folks who are multiple feet away from the phone during a standup.
When you do your demos of working code for stakeholders at the end of the iteration, use webex or livemeeting or something to share the desktop and a camera to show the speaker so that your distributed participants can see what's going on. (Even better would be to ask your telecommuters to attend during iteration boundaries to participate in person).
I recommend getting folks together for a few weeks at the beginning of the project during the inception/kickoff phase so folks can build interpersonal relationships. It's amazing how helpful the face-to-face interaction up front can be to build a foundation for teamwork.
Use a distributed card wall. I like Mingle (http://mingle.thoughtworks.com), but I haven't used other tools, so can't comment on them.
For retrospectives, it's useful to have a proxy in the room using IM to communicate with your distributed team members... so that any comments the distributed folks have can be written onto a piece of paper (or post-it, or however you do yours).
As for your fears of "out of site, out of mind", my preference for things like this is to not create solutions for problems that have not yet materialized. If you find that your team is becoming disconnected (prime discussion points for retrospectives), then you can facilitate a team discussion on how to deal with any issues that arise. Again - the team should help identify the problem and the solution rather than having a manager or scrum master dictate solutions. Start with an assumption of trust.
Distribute Scrum requires good preparation. It is not just about the tool.
We supported many rollouts in distributed environment and there was one fundamental point - people.
The most efficient is to start with ALL people in one location. They have to meet in person so they can know each other as persons, not just someone virtual on the other side of the world. As I used to say - team members need to smell each other.
For release planning meet at one location, if possible. Change locations so you visit all of them, to have a context and understanding of culture, habits, persons. For sprint planning use video meetings, screen sharing etc. It is not necessary to travel (it would be too often).
Clear roles and team(s) organization must be established. You have to have Product Owner and Scrum Masters. You should consider if you do not want to get PO & SM as close to the team as possible. Definitely you have to get them into face 2 face meetings (it is about face, not a location) every day.
Definition of done, if agreed by the team, helps to have the same understanding what Done means. In distributed environment is a must.
You will need a good communication tools for daily stand-ups . We found usable to use Skype or Office communicator for dailies. We use audio AND chat. Especially in international environment chat allows you to understand people. Keep communication channel open after daily so team members can discuss what is necessary outside of daily report.
And, the most important, is to do regular retrospectives with all team members in all locations. Do not forget to implement ideas coming from retrospective. Teams in other locations will need a local support who will help them to implement ideas.
I work on a team of 5. We to facilitate our telecommute workplace we use:
Asana - Project and Task management
Google Talk + Your favorite IM
client (I used Pidgin)
RingCentral - VOIP Telephone
Gmail - asynchronous communication (i.e. email)
Dropbox - file transfer and
backup
Team Viewer - Screen Sharing, Training, and Presentations
Even with these tools it is easy to fall short on your process so it is important to establish some best practices for your team based on your dynamic. For example, we have two chief practices:
Communicate Often - because we are not in the same location when communicating it is easy to forget that you are working on a team. For our team, we update our tasks in Asana with comments describing ideas, obstacles, and task completeness. When immediate assistance or feedback is needed, don't wait, seek assistance via IM or email if (the person is offline).
Lean on the side of over communication - This pertains more to Asana comments and emails. However, in general we found it is better to give more information than is needed (within bounds).