The Grand Multiplayer Thread

Hi BenderB,

Need to write a server-side plug-in? Yes

Why do incomming messages also have time stamps? A game player should never be trusted to assign a time to something that gets sent to other players. The server is the time controller. If playerA wants to shoot, then he sends (in this case) a Shoot move to the plug-in. The plugin knows where that character is and determines what to send the other players and sends it.

Different execution times and each computer? Not if you do it right. A speed of 10 does not have to mean 10 units/frame. More likely it would be a speed of like 200 and that is the number of miliseconds that it should take to move from the center of 1 tile to the center of an adjacent tile.

the reason a time stamp is needed is because flash gets the time on the system, so two different computers will give the game two different times, and hten one game will think that it receved the message before it was sent.

Ihoos: But if the server sends his time at the beginning of the game to the clients, the clients could create a new Date() object with the time transmitted from the server.

The point is, I guess, that by resetting the time at the clientside it would be possible to cheat.
But if I'd only "stamp" the messages at the server I wouldn't have information about the time passed since the client sent the message to the server...:confused:

thanks again,
BenderB

BenderB,

You want the server to be in control. Therefore the server doesn't care how long the "shoot" message took to get from a client machine to the server. When the server receives the shoot message it then:
1) verifies that the user has ammo
2) updates information about the game in memory
3) creates a message to send out to everyone in the game, and sends it

The person that attempted to shoot in the first place also receives the message from the server instructing the game to create the shot. Under reasonable conditions this can all take place in about 1/3 of a second.

i agree with jobemjobem. event if it takes half a second to transmit the information from Client A to Client B, and therefore the characters arent in line anymore, who will be able to verify this. in shooting games the bullet moves a bit random anyways, so its impossible to say if it hit the character or not.

and as jobemjobem said, if the screen isnt updated when he shoots, but when the server agrees and send the file back, then the bullet will actually hit anyways. this will be a problem if the ping is large, so the character onscreen lags. but not even my first method can fix that, cuz then you might die even if u have shot ur opponent. i think the server should be in control.

Jobe:

I made my first attempt in writing a server plug-in.
I read your article on your website which says:

It goes without saying that many ActionScript classes are not supported, such as: MovieClip, Sound, Color, etc. For the most part, you have access to objects, arrays, variables, math functions, dates, SharedObjects, LoadVars, loops, Booleans, numbers, strings, setInterval, functions and a few features not seen in regular ActionScript. Some extra features are the abilities to talk to other plug-ins, read files, write files, create directories, kick a user, ban a user, etc.

But there seems to be no documentation on how to use the extra features or which classes are not supported.
I tried to load my map with the XML() object but I only get an error message from the client:

-----incomming----
<XmlDoc><Action>ERROR</Action><Parameters><Result>Failure</Result><Reason>You have specified a room that doesn&apos;t exist</Reason></Parameters></XmlDoc>

Seems the XML() object isn't supported. :confused:
But how is it possible to read files then??

Hi BenderB,

Sorry for the late reply.

Yes, sadly the XML class is not supported either. Not in the ActionScript plug-ins.

ElectroServer 3 is actually supports like 95% of JavaScript, and JavaScript does not support XML, which is why these plug-ins do not.

If you want a plug-in to load external data, then there are 4 possibilities that I can suggest:
1) Load from a database. The data would have to be returned as name value pairs.
2) Load from a server-side script (name value pairs)
3) Load from a some text file (name value pairs)
or
4) Load using server-side SharedObjects.

I want to mention a little about #3 and #4. But first let me tell you that I have attempted to attach a zip file with documentation on this server-side stuff. If its not there and you need to email me to get it, then email me at [email protected]

You can read a server-side file like this:
var contents = readFile(“some_directory/myText.txt”);

The contents of the file are loaded to the contents variable. Once loaded, you have to figure out for yourself what you want to do with it.

Also, I programmed in support for server-side SharedObjects. This could be useful for you. Here are 2 actual functions from a plug-in that I haven't written an article about yet. It saves/retrieves a high score list as a shared object.

Code:

---

function loadHighScores() {
        //Load the high scores shared object
        //  The first param is the name of the object, the second is the path to the object
        ScoresOb = SharedObject.getLocal("HighScores_example", "plugins\\");
}
function saveHighscores() {
        //The 'flush' method saves the shared object
        ScoresOb.flush();
}

---

The shared object serializes the data and stores it in a text file. When retrieve it deserializes the data and gives it back to you as an object.

The reason why I am giving this to you as an option, is that you could create your map using some map editor that you build and serialize it. Then put it on the server and load it that way. If you are interested in that then let me know, I'll have to send you the serializer, its not WDDX.

As always thanks for the greate help you offer jobe!
I'm really out of money at that time, so the least thing I could do to support your efforts was to suggest our university library to buy a copy of your book and they just told me they ordered one.
Can't wait to have a look at that....

Anyway, back on topic:
I've been thinking about the options you described to implement the map loading on the server side.
The thing is, that trying to move the gamelogic to the server would be hard work from my current level of knowledge.
It's not shure if the network gaming would be fast enough then (as that would be why I would try this whole thing), so I decided it would be best to stick to the client side logic and play around with methodes to increase the speed and flow of the game.
Time is running out and we have to put in hard work to realize everything we had in mind, so it's too risky for me to spend another 2 weeks or so to get the logic on the serverside only to find out then that it might be to slow anyway.

So thanks for the help and I'll be right back with a load of bugging questions.....;)

BenderB

Ok. But take my advice, if you are doing *only* client-side logic, then make the game turn-based. If you try to make it real-time then you will get an ulcer trying to get everything working properly.

That sounds like I *have* to implement some logic on the server.;)
I'm really in a crappy postion now...

I thought it over, and I don't think it's possible for our type of game to split the game logic between server and client, just all or nothing.

So....let's get back to server side logic:

It's really a bit hard for me to imagine how the server could deal with the information corretly so I'll just write what I can imagine:

Basically the server is running the game.
Before the game started the players defined on witch map (out of say 5 to 10) they want to play.
The Server then loads the Array of the map (as this is Tile Based) as well as the clients load the map, but they also render the map on the screen.

All that the clients do is to send data to the server if a move is made (moving, shooting,...), and to receive data from the server if a character should be moved, a shot should be created, and so on.
So if the Server receives a message from a client that he wants to move his character to the right, the server checks on his Array if the move is legal and if it is, he sends data to the clients where to move the character including a timestamp that indicates when the character should be at the next tile.

To guarantee that the games are synchronous the server and the clients need to move the characters in the same time (setInterval???).
If I would deal with the communication by sending a message when the movement began (key is pressed) and sending a message when the movement is over (key is released) it would require that the game is really synchonouse as otherwise the collision detection (which is happening at the server) wouldn't work properly.
I'll guess that every now and then an update with the current position of the player (at the game of the server???) would need to be sent out to the clients.

Because there is no game loop on the server I guess something moving continuously (like a bullet fly...) has to be implemented some other way.
Is setInterval a good option for this?

Also it's a bit hard to imagine for me that if every move has to be transmitted to the server first and back to the clients that the game would work properly as the traffic would be intense I guess...

thanks,
BenderB

P.S.:
The "game design demystified" book arrived.
Great job on that one Jobe!

Hi BenderB,

setInterval works in server-side ActionScript plug-ins. The only thing is that you have to specify the string name of the function, and it doesn't accept parameters. For instance, this is legal:

Code:

---

function moveBullets() {
        for (var i = 0; i<bullets.length; ++i) {
                var bullet = bullets[i];
                bullet.x += bullet.xspeed;
                bullet.y += bullet.yspeed;
                checkForObjectCollision(bullet);
        }
}
function callEveryFrame() {
        moveBullets();
        //moveCharacters();
        //something else
        //more stuff
}
var id = setInerval("callEveryFrame", 30);

---

When someone shoots (and its valid) you create a bullet and add it to the bullets array. When it collides with something you remove it from the array.

Here is how I'd handle moving characters:
1) Continuous movement is not possible.
2) Movement is tile-based. If you press the right arrow, then you walk to the next tile over. If you hold the right arrow down, then you progressively walk tile to tile. Every time you reach the center of a tile its like you pressed the arrow again. So its not really continous. Regular continuous motion (no boundaries) is not good for real-time games in Flash because of the unpredictability of where a character can exist and the amount of information transfered will increase greatly. Also, the latency will be more apparent because its more of a twitch style game.
3) When you press the right arrow to move, the move request is sent to the server. The server verifies and broadcasts that that character shoult be animated from one tile to another.

In my game (which is going slowly right now due to other projects), we allow you to click on a destination. A* pathfinding calculates a path and that entire path is sent to the server. The server verifies and if valid broadcasts it. That is great since it is 1 transaction that potentially covers 1 - 5 seconds of movement. This makes the game feel much smoother.

Quote:

---

Originally posted by jobemjobem
1) Continuous movement is not possible.
2) Movement is tile-based. If you press the right arrow, then you walk to the next tile over. If you hold the right arrow down, then you progressively walk tile to tile. Every time you reach the center of a tile its like you pressed the arrow again. So its not really continous.

---

So that would mean that there is at least a delay of two messages sent to, and from the server before a player can move to the next tile.

As the Server sends out the messages with a timestamp when the player should arrive on the next tile, are you just speeding the movement on all clients (because of the time that has already passed) up, so that the speed at which the player is moving to the next tile depends on how long the message took?

Oh, and another question that was bugging me:
Why do I have ping times between 100 and 300 ms when I'm testing the game (with two games open) on my own PC?

thanks,
BenderB

BenderB,

Yes, there will be a tiny delay if you let someone hold down the arrow key and you send the "walk" message once per tile. But that is better than sending your position 10 times per second and having to have each one of those verified.

It is not a good idea to do speed tests with 2 SWFS open on the same machine. You will not get good results. I use a PC and a laptop for testing. If you run 2 SWFs on the same machine you'll nearly half the response time. This is ok for testing turn-based games though since delay doesnt matter.

Another thing to note is that Flash is intensive to a CPU. So if you have ElectroServer 3 running locally plus 2 SWF files, ElectroServer 3 might actually slow down too.

I know that most people don't have the luxury that I do for a good testing environement. But I have 3 computers here plus I have ElectroServer 3 running on a remote dedicated server. That way I am developing against something closer to what it will be used as when the game is launched.

Hi!

I've encountered a problem with the plugins:

I've taken the code from the SimplePluginExample which is delivered with Electroserver and tried to modify it to test the plugin I wrote.
But a really weird thing happens when I try to test it.
When the program has finished loading I can submit messages to the plugin and receive something from it.

PHP Code:

---

---out going----
<XmlDoc><Action>ExecutePlugin</Action><Parameters><Plugin>InYourFace</Plugin>
<Method>Calculate</Method><Variables><Variable><Name>iterations</Name>
<Value>10</Value></Variable></Variables></Parameters></XmlDoc>
-----incomming----
<XmlDoc><Action>SendPluginMessage</Action><Parameters><User>InYourFace</User>
<Message>test</Message></Parameters></XmlDoc> 


---

But after a short moment this message arrives:

PHP Code:

---

-----incomming----
<XmlDoc><Action>ConnectionResponse</Action><Parameters><Result>Accepted</Result></Parameters></XmlDoc> 


---

and from then on I only get error messages if I try to trasmit something to the plugin:

PHP Code:

---

---out going----
<XmlDoc><Action>ExecutePlugin</Action><Parameters><Plugin>InYourFace</Plugin>
<Method>Calculate</Method><Variables><Variable><Name>iterations</Name>
<Value>10</Value></Variable></Variables></Parameters></XmlDoc>
-----incomming----
<XmlDoc><Action>ExecutePlugin</Action><Parameters><Result>Failure</Result>
<Reason>The specified plugin was not found</Reason></Parameters></XmlDoc> 


---

The Plugin should work because I tried to simply exchange the Plugin name in the SimplePluginExample and it works.
But the only difference in my current file is that I load a map with the characters, other than that I use the exact same code as in the SimplePluginExample.....

any ideas??

thanks,
BenderB

Hi BenderB,

If you get the ConnectionResponse message, then you must be accidentally reconnecting to ElectroServer. That is the very first message received when you connect.

If you are reconnecting to ElectroServer accidentally, and haven't logged in, then that is why its not finding the plug-in.

Alright, again I screwed up.
I put in a gotoAndPlay() instead of a gotoAndStop() and it jumped to the first frame of the timeline.....:rolleyes:

thanks,
BenderB

Hi again Jobe, and yes, I won't give up....;)

1.)
In the ES documentation at 'createRoom' at 'UserVariablesEnabled' it says:

PHP Code:

---

If blank or 'false' then user variables are not enabled for this room (increases performance).
If 'true', then user variables are enabled for the room. 
See createUserVariable, login, or userVariableUpdated for more information. 


---

I searched the document but there doesn't seem to be any description of 'createUserVariable' or 'userVariableUpdated' and at 'login' there is no information about the user variables.

As I want to store information of each player and his character (and want to transmit this info to the server at the beginning) I thought these could be usefull.....any info?

2.)
I have so far set up the basic interaction between server and client with the logic on the serverside and I works perfectly!
I'm now implementing the timestamp-thing.
Before the game starts I send the actual server time to the clients which they store.
Whenever a message is sent from the server to the clients I include a timestamp so that the clients can determine when the character should be at the next tile.
I've searched for a good way to do this but the only thing I could come up with was this:

When the clients receive the time from the server at the beginning of the game, they store it in a variable called 'InitTimeServer' and they also store their current time in a variable called 'InitTimeClient'.
If during the game a move is sent from the server to the clients a timestamp with the current time + the time the character should be at the next tile (the speed), on the server is included which is stored in 'variables.timeStamp'.

A client can then calculate the time the character should be at the next tile by calculating:

PHP Code:

---

InitTimeServer + ((new Date()).getTime() - InitTimeClient) - variables.timeStamp 


---

But that would cause that if the ping at the beginning of the game, when the server time is transmitted would be very high, every move in the game would be inaccurate.
Or have I screwed up again and there is a simply solution....

I don't know if I have expressed myself clearly or if the above makes any sense but if, I'd like to here your oppinion on that topic.

thanks,
BenderB

i am actually working on a mulitplayer game for online use with flash. i am currently going the route of electroserver. its perfect for my needs and lets me concentrate on the code, plus i don't plan on having more than 20 people playing at once.. so it gives me the freedom to play with what i need. once i get a beta thing finished i will post it up... its a great concept.

Jobe:
Sorry I might have asked too much.....

Anyway I'll figure out the timing thing but it would be nice if you could give me a hint with the userVariables.
I played around with them but I can't get the userVariableUpdated event fired.
In the documentation there is a function called createUserVariable but there is no description and I can't get it to work.

And another thing.
Is it possible to access roomVariables from a room I haven't joined yet?

Thanks,
BenderB

Hi BenderB,

Actually, I didn't know you had that other post. Somehow the Flashkit message must have been deleted with my spam...which I still do manually.

Apparently there is some sort of a bug with the user variables. I'll have to check that out over the next few days. I'm on my way to NYC this morning and won't be back until Tuesday night. So don't expect a quick response.

Good luck!

Thanks Jobe!

I wouldn't go so far and say there's a bug with the user variables it's just that they aren't described in the documentation and when I use them the same way I create room variables it doesn't work....

And of course I have another question:
I played around with room variables and room attributes for the last couple of hours and I'm not shure if I got the difference between these right.
Is a room attribute only modifiable through the person who created the room or can any client modify them?
I assume that room variables can be modified by any client and in addition the roomVariablesUpdated event is fired.

Is that correct?

Thanks,
BenderB

Don't leave Coldfusion out!

-T

Jobem, i just downloaded ES 3 and im thinking of making a multiplayer game. the first game ill make is my racing game, and im thinking of testing everything in the game, end just send the x and y variables (ok, maybe rotation too) to the serveronce a sec. then it sends it on to the other user, who tweens it from the previous position. at the end of the race both players will send their time to the server so it can check who won. im not planning to have any server side sripting for this, but is that a good idea? and another thing. ive downloaded the ES 3 (as i said) but if i want it on my new server, do i need to upload everything or just the star, stop, settings and stuff? and since i have the free version im only allowed to have 20 people at the same time, but in the xml file (configuration.xml) cant i just change that number from 20 to 2000?

Hi BenderB,

Yes, there is a bug with the ElectroServer class file with user variables. The server handles it properly, but the class doesn't. I'll be uploading a fix in the next week and will let you know.

Room variables can be created by anyone in the room. But there are attributs to a room variable, such as locked = true or false. If locked=true, then the room variable can not be changed, but it can be deleted and recreated. If locked = false, then it can be changed by anyone. If deleteOnExit = true, then the room variable will be deleted when the user that created it leaves the room. If deleteOnExit is false, then the variable will not be deleted when the user leaves the room.

All room variables are deleted when a room is removed. A room is removed when no more people are in it (unless it was a persistent room).

Room attributes can be changed by anyone in that room.

Hmm... Loadsa stoopid questions:

Tested out electroserver locally, it works great, impressive stuff...
I put in my 'global' IP address into all the neccessary places and the server doesn't start properly...

I was wondering if this was because:

a) I have a router with inbuilt firewall.
b) I have to change the port number.

All I wanna do is get the chat example supplied with ES up and running and I will be more than happy!

When I want others to be able to connect do I just run ES from my desktop and wait?

Thanks for helping a total noob.

w.

Hi problems4me,

Glad you like ElectroServer 3!

Ok, so you say you changed the IP everywhere. Is this the IP of the computer from which the server is running? It sounds like you are running it from your own PC. If so, then the IP must be the IP of your PC.

Once you answer that I can try to help further.

i tried the game and i also tried to modifie it into my own game, but i had one problem. this line

Code:

---

es.sendMove("all", ob);

---

sends all of the variables in ob, but what if i only want to send some? like the _x and _y and _rotation? and can u please write a book or tutorial on electro server (yes, i have visited the website).

p.s. great book. looked through it at my book store. top of the list for chirstmas :D

Ihos,

The complete object is serialized and sent. The trick is to only put in it what you want to send.

For instance, if you have lots of variables stored in myObj but you only want to send 3 of them, then you should do this before you send:

sendObj = new Object()
sendObj.x = myObj.x
sendObj.y = myObj.y
sendObj.rotation = myObj.rotation
es.sendMove("all", sendObj)

Good luck

thanx.

how fast is ES? as in, how often should i send data in a real itme game?

Ihoss,

It screams. ElectroServer 3 appears to be just as fast as any socket server around, including what ever servers they use for games like Quake and Half Life. The main latency factor is in network latency, which has nothing to do with ElectroServer 3.

There is no simple answer for how frequenlty you need to send data in a real-time game. Real-time games are extremely custom--they depend on tons of factors to be done correctly.

If you have never created a multiplayer game before then I extremely encourage you to start with a turn-based game.

FYI: If you are going to be at Flashforward 2004 in San Francisco this year then come to my session. I am doing one on real-time gaming in Flash.

can u just send all of the stuff u do there to norway, real time ( u should know how to :D )

yeah, ill probably start with turnbased. i got a great idea though:

at the beggining of the game player one (the one that challenged the other or the first one to join the game) sends all the data about all of the characters on screen to the server which passes it on to player two. when player two recieves it he parses it and sends the new data back to the server and to player one and so on.

Yeah - trying to run it off this computer, but it is networked, would it be easier to run it off the computer directly plugged into the modem, or does it make a difference?

The IP I need is the one that is shown when you go to whatismyip.com right?
I have all sorts of IPs, gateway IPs, subnet mask IPs, Connection IPs.. which 1 is it!?
The 1 I tried was the one you get shown at whatismyip.com, but as I said, electroserve was just laughing at me!

W.

Hi problems4me,

I definately am no network expert, but here is what I do know:
- The IP points to your network
- Internally on your network, all computers have an internal IP
- You must do what is called "port forwarding" on the network. So when an external request comes to your network on port 9875, the network router knows where to forward the request.

Most (if not all) routers have the ability to do port forwarding. You would configure the router to forward all requests that come to the network on port 9875 to a specific internal IP.

ok, I set my IP in the configuration file to 217.44.**.*** (my IP as seen by others on the net)

I then forwarded 9874-9876 and 8079-8081 to 192.168.*.** (Internal IP of this computer)

I open up StartElectroServer and get this:

http://www.stylishdesign.co.uk/sses.gif

:(

Such a simple thing to do, yet I can't do it :(

Hi problems4me,

Ok, I *think* the problem is that you are trying to bind ElectroServer 3 to an IP that it can't see, because it is inside the network. I think that you must bind it to your internal network address.

So, if your internal IP of that computer is like 101.102.103, then you'd bind it to that IP and the normal port that you are interested in using. Then you should hopefully be ok.

In order for someone external to connect to ElectroServer 3, they'd have to use the IP of the network itself.

Give that a shot, shouldn't take you abut 30 seconds to change.

im trying to test es on my network too, but i get the same as Problems. i also noticed that theres a chatServer and a webServer, which one should i change?
ive used my ip on the network but i get the same error as Problems. in the network properties (win XP) theres something called network mask (translated from norwegian windows). could that have something to do with it?

i also tried to make a realtime game the way i described it above and it worked on my comp (only one way though, cuz i havent been able to fix the turn taking :D )

Hello, I'm another Electrotank lackey coming out of the wood work. Jobe is right. The issue is simply that you are telling the server to bind an IP address that isn't available to it. You can tell what your IP address is by clicking:

start --> run

then typing in "command" and pressing enter. At the prompt, type "ipconfig" and press enter. This will work on Windows 95 and up through XP Pro. If you are on Linux/Unix, then you wouldn't need these directions. If you are on OSX then I am not sure how you find the IP. The results from "ipconfig" will look something like this:

C:\DOCUME~1\MIKE>ipconfig

Windows IP Configuration

Ethernet adapter Local Area Connection:

Connection-specific DNS Suffix . : abc.xyz.com
IP Address. . . . . . . . . . . . : 192.168.1.105
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.1.1

C:\DOCUME~1\MIKE>

The "IP Address" listed is what you should be using for both the chat and web server setting in the configuration file. Make certain that you use different ports for each. I recomend you disable the web server if you're not using it.

If your computer is connected directly to a cable/dsl modem without any sort of software/hardware firewall, then you are done. If you have a linkSys or other router/firewall or a software firewall then you are half way.

To open a firewall you need to specify a rule that allows for any external IP inbound access to the IP/port number you specified in the config file. The specific way to do this depends on the software/hardware in question.

To let people through your router/firewall combination you will most likely need to use port forwarding. It is sometimes called other things by the various vendors (consult your documentation). The idea is that you have an external IP address that everyone on the Internet sees pointing at your router/firewall box and then you have internal addresses that only your network can see also pointing at the router/firewall box. This is done for security reasons. Rather then get into the technical details, suffice it to say that you need to tell the router/firewall box to "forward" all requests to it's external address to an internal network address. In my Linksys router, it says something to the effect of "external port", "internal port", "protocol" (either UDP or TCP) and "IP Address". Based on what the "ipconfig" command told us and my own ElectroServer configuration, I put in this:

External Port: 9875
Internal Port: 9875
Protocol: Only TCP
IP Address: 192.168.1.105

That's pretty much it. The black art of opening ports up :)

Have fun!

Mike Grundvig
Electrotank, Inc.

When I put the IP address in that you speak of, the server loads up correctly on my computer...

I test it by putting in the same IP into the chat thingy, it works fine then...

Then I go to putting in my 'global' IP, and it just laughs at me.

I have poked holes in my firewall as so:
http://www.stylishdesign.co.uk/multiplayer/ports.gif

Is there any way to test if this poking has been successful?

If you want to stare at the chat swf trying to connect go here:
http://www.stylishdesign.co.uk/multiplayer/Chat.html

This is how you say it works right?:
Global IP in chat.swf > IP shown in ipconfig (thanks to port forwarding) > ES > SUCCESS

W.

problems4me,

In this HTML page http://www.stylishdesign.co.uk/multiplayer/Chat.html

edit the HTML so that it embeds the Chat.swf by using the IP.

So, if your IP is 206.33.104.63, then the HTML page embeds this SWF file:

http://206.33.104.63/multiplayer/Chat.swf

problems4me,

Actually, I was assuming that the IP of your domain is also the IP of your computer. Is that not correct? If they are different, then there are only 2 ways that a SWF can connect to your computer's IP.

1) The SWF must be loaded from your computer's IP.

or

2) The SWF can be loaded from your domain, but your computer has to serve up a policy XML file that gives the domain access to your computer.

I probably just confused you more, but I hope you follow :)