The Grand Multiplayer Thread

Hi BenderB,

There is 1 very important thing to realize about real-time games and latency. It has almost nothing to do with the server or Flash. It has 99.9% to do with the network speed/Internet speed of each individual game player.

Flash has the same ability to do real-time games as Director, or even games like Half Life or Quake. The key is how you display the partial information that you need to keep loading.

In games like Quake you see characters smoothly walking around. But you are not receiving the information that smoothly, the game just takes the information bits and smooths the motion. The same must be done in Flash, its just that most people don't realize this.

But there is another issue here. How many multiplayer real-time sports games have you seen on the Internet? Basketball, football, ice hockey,....doesn't really happen. There is a reason, the network/Internet latency is too large for precise games like that. With limitations you could do some of these games. I believe that soccer could be done.

But I do not think that foosball (table soccer) could be done...within reason. Titoonic did a good limitation on that game to get it to work. Try pegball.com

If you can think of a game where the characters don't have to be really high speed then it will probably work.

Good luck!

Thanks for the quick and informative reply jobe!
(Although I'm left without a project idea now...;))

My fellow project members and I still want to make a multiplayer flash-game so we are looking for a new idea now...
Would it be possible to make a multiplayer game in the style of Bomberman (isometric view) but with Teams (up to, let's say 8 players) and different game modes and maps??

And another question, would it be possible to make the foosball game runable in a LAN (as there would be very little latency)?

thanks, BenderB.

HI,

Bomberman with teams: extremely doable. Of course, like all games, you have to put in hard work to get everything to flow correctly. But that is the perfect type of game. The game does not hing on having to see exactly where the other players are. A little bit of a delay will not ruin the game.

Foosball on network: possible, but I wouldn't guarantee it.

Wow, thanks again for the quick answer!

Let's see if we can come up with a good idea how to make it...

thanks,
BenderB

..and there I am again.

We started our little "Bomberman plus" project and so far I made the first simple stage with 2 players (thanks to Ed Mack and his great tutorials).
The main problem of the whole project is still the multiplayer part, so we decided to test it out in this early stage to avoid reprogramming at the end.
I downloaded the free ElectroServer and installed it but when I try to start it, it hangs up at:

PHP Code:

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-=-=-=-=-=-=-=-
Starting Chat Server
Chat server will listen on ***.***.**.**:9875 //ip-address removed...
Attempting to bind chat server address...
Successfully bound chat server address
Client queue: input=1000, output=5000, msglimit=50
Thread pool started: min=1, max=10, keepalive=60000
Chat server listening for inbound connections... 


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I kept the standard installation parameter and entered my ip for the Web-Server ip.

Another question:
Is it best to submit any change of one player through the server or do I have to additionaly implement a timebased synchronisation, like every 2 seconds???

thanks,
BenderB

Hi BenderB,

That means that the server started up properly. I wrote an article on it here:
http://www.electrotank.com/ElectroServer/articles1.aspx

You can compare the screenshot to what you are actually seeing. They should be similar, if not the same.

If you installed ElectroServer 3 and then start it up, you should be able to try any of the test applications successfully. Go to Start > Electrotank > ElectroServer 3 > Examples

On that page you can click to view any of several example files.

Regarding your other question, I'm not sure what you're asking.

Sorry for being so stupid.
I typed my IP for the Web-Server IP and tested the examples but I only got a "couldn't connect to server" message, so I assumed the server must have been hung up.
I didn't realise the IP is set in the FLAs of the examples, so when I changed it back to 127.0.0.1 it worked.....:rolleyes:

I think it's best if I'll test out what I had in mind before I'll ask anymore stupid questions.....;)

thanks,
BenderB

Havent had a computer to work on for like 6 months, but now im back.

first of all, what is the difference of XMLSocket and XML? and does the socket script send all the variables to the server or just what you specify. i havent used socket servers before, but ive downloaded the Elecktroserver and ill try it soon.

btw, my multiplayer game is soon finished. the reason it took so long is that i have to do a lot of things at the same time. one week ill work on the gaem, the next on my website and the third ill work in 3ds max. i asked about php in like february or something and ive learned a lot about it, but still, isnt it very slow to access a mysql database (or any other for that matter)? ive seen that it really slows down the execution of the script. and someone said that with database many people can access it at the same time (i think it was Ed Mack). But can a server send a php file to more than one person at the time? i think ive heard that it cant, but i may be wrong.

XML is a way to format information. For instance, XML for an address book could be something like this:

Code:

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<AddressBook>
        <Entry>
                <FirstName>Jobe</FirstName>
                <LastName>Makar</LastName>
                <Email>[email protected]</Email>
        </Entry>
        <Entry>
                <FirstName>Mike</FirstName>
                <LastName>Grundvig</LastName>
                <Email>[email protected]</Email>
        </Entry>       
</AddressBook>

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A socket is an open connection that can transfer data. There isn't really such a thing as an XML socket. Its just that Flash can connect to a server on a socket and it is built to pass XML formatted data, hence XML Socket.

Files cannot be passed.

sorry, ill refrase my question. in flash, under client/server you got XML and XML Socket. what is the difference between these two? how can i use the XML one?

Hi!

I've used the last week studying the Electroserver class and making a simple testing game.
It contains a simple tile-based map on which two almost identical characters are placed.
Each character can be controled by different user on different computer.

First I sent the x and y coordinates of one user to the other everytime a move was made.
This was, as I expected, very slow.

Then I tried to send only the beginning of a movement(when a Key is pressed down) and the end of the movement (when the key is released).
In addition to that I sent the absolute coordinates every 1 or 2 seconds to synchronise the movement.

The problem I have with this method, is the following:
User #1 presses the left key and the steps in which his character move (for example a quarter of the size of one tile) are being transmitted to User #2.
User #2 gets the information and moves the character of User #1 on his screen according to these steps until he receives that the key was released (for example 8 pixel to the right everytime he enters the frame).
But because the stepwise movement of the characters depend on the speed of the computers, the character is moving much faster on the one computer than on the other.
I would need to synchronise the execution speed of the two users.

How can I do that???

Is this a good method to make the movement smother and more accurat or are there better ones?
I heard of a method called "dead reckoning" which is used in fast multiplayer games.
Could this method be usefull for this kind of game (bombermanclone with different weapons and more player)?

thanks,
BenderB

P.S.:Please excuse my bad english....

what u could do would be to make a variable called time which contains the microtime (or is it milliseconds? one of them is it anyways), on #1s computer, and send it to #2. Every second send the two x/y and time. when #2 recieves the time it checks if the time lapped on his computer is the same as #1. if it has, then it moves it to the new x/y. i havent tested this, but it think it will work.

Hi BenderB,

In general, there are 2 ways to pull off real-time character movement in multiplayer games:

1) Make the movement quantized. Sure it might take 5 charcter steps to move from the center of 1 tile to the center of an adjacent tile. But when the user presses an arrow key you just send the destination tile to the other players. So by controlling a character you are just moving him tile to tile. The character only stops at the center of a tile. This can work *really* well, its how we are pulling off a very cool game that we're working on now.

2) Dead-reckoning algorithm. This isn't so easy. This is for non-quantized movment, known as continous movement. With continuous movement the character can exist at any point (within reason), not just in the center of a tile. The key here is that all characters broadcast information about themselves when it changes, but not more frequently than some amount. The other client machines use the recent history of your characters movement to determine where he will be moved on the next frame. For instance, you might send information to all players about your character such as:
x=100, y = 100, rotation = 270, speed = 4
The other client machines update your character to show that information and then continue him at a rotation of 270 and speed of 4 until another update is received.

Dead-reckoning algorithms can be complicated. I have never built one, but there is no reason why it can't be done in Flash.

Good luck

Thanks for the quick replys again!

Jobe:
From what you wrote it seems that the first method seems appropriate for the kind of game we have in mind.
But if I transmit only the tile on which one player is going to be next, the problem is still that the speed in which the animation to go from one tile to the next is different for the players.
For example, if User #1 would hold the up key pressed his player would appear to go smooth upwards until he releases the key.
But for User #2 the character of User #1 could appear to go from one tile to the next then stops (if the script to move the opponent is faster than the script to move the own player) then it would go again and stop and so on.
It would depent on the time of the different scripts and the speed of the computer how long the transition from one tile to the next for the opponents character would take.

Any suggestions?

thanks,
BenderB

P.S.: I'm curious to see the game you are working on!

BenderB,

Yes, I understand.

In our game we have implimented time-based movement.

The server knows what time it is. At the beginning of the game it tells each client what time it is, for synchronization.

Every move goes through the server and the server gives it a time stamp.

All characters walk at 1 of 2 speeds. We send the time that the walk starts, the speed of walking, and the destination tile. With that information all of the other client machines can precisely move the character to the end tile.

Client A sends a "walk" move
Client B receives this "walk" move. It took, say 1/4 th of the walk cycle to even receive the message. Well, since this is time based we know how long it took and just move the character to where it should be.

With this time-based method you are never more than 1 latency jump behind. On most modern set ups with good network connectivity, the latency should be 80ms to 200ms. Therefore, on a reasonably good set up, no client should be more than 1/5th of a second behind.

If you recieve a message and determine that the character should have already arrived at the destination, then you just plop him into the destination.

Hope this helps

that is what i was on about, but which i could exlain very good. but if client A sends the movement data at time 256 and Client B recieves it at time 258, would he then speed up the movement of character A so they reach their destination at the same time, or does that not matter very much?

ilhos,

It depends on how you want to do it. The 2 basic choices are:
1) Just pop the character into the spot that he is supposed to be in.
or
2) Change the characters speed so that he starts at the starting position and reaches the ending position at the correct time.

In my game I use a combination of the 2. You dont necesarily just move 1 tile at a time. You can click somewhere and move a bunch of tiles. So you move tile to tile. On the first tile I speed the player up to reach the desitnation at the correc time. Then for all other tiles I use the correct speed (because presumably everything is now synchronised)

smart. ive also noticed that when i play battlefield online and theres a lot of lag, the other characters jumps backwards again after moving. does this have something to do with the second option (smoothing out the movement)?

Just depends on the program. Some do no smoothing, so all you see is stuff blipping around. Others do lots of smoothing. Most do a combination.

In many first person shooters you see what appears to be smooth running. But occasionally people blip around. Its really not as smooth as you think. They are tricking you by filling in the gaps of information with best guesses.

..and again I'm here for some bugging questions ;)

Quote:

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Originally posted by jobemjobem
The server knows what time it is. At the beginning of the game it tells each client what time it is, for synchronization.
Every move goes through the server and the server gives it a time stamp.

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If I understand correct that means I'd need to write a server-side Plug-in for the Electro Server.
Also why would you need to put a time stamp on the message if the player includes the time he sent it into the message anyway?

Quote:

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All characters walk at 1 of 2 speeds. We send the time that the walk starts, the speed of walking, and the destination tile. With that information all of the other client machines can precisely move the character to the end tile.

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If you send the speed of walking (let's say speed=10) the execution speed of the script would still be different on two different computer (or even between the script that handles the own player movement and the script that handles the oppontens player movement).
Or should the time on which the player will arrive at the next tile be transmitted?

Quote:

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Hope this helps

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It shure does a lot!

Ihoss:
Thanks for your help.
I just didn't get the point of your first reply! :)

thanks,
BenderB