Author Topic: Desync in multiplayer? Check this first.  (Read 16136 times)

Offline x4000

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Desync in multiplayer? Check this first.
« on: June 04, 2009, 04:51:49 PM »
Desyncs are an issue that can only happen in multiplayer games; they basically consist of the simulation getting out of sync between the different computers in the game.  If this occurs, the game will stop and the host will get a little white message that there was a desync (along with being able to see which player the desync was with).

Is it really a desync?
The message "Waiting For Players" sometimes mistakenly gets called a desync when it is not.  That message can mean any number of things, such as players having quit the game, players not having joined yet, a player having lost a network connection, a player's wireless network connection losing some data but not the whole connection, a router or network card or ISP causing an infinite-resend loop due to strange MTU settings or similar, or a variety of other things.

Only the host of a game can know for sure if it is a desync.  They need to click the Stats button and look on the Players tab (selected by default).  If there is a desync, they will see the word DESYNC in the Status column next to one or more players.  The players with the desync next to their name are the ones that have desynced.  If all players have desync next to their name, then the host desynced.

If it is not a desync:
Then you need to troubleshoot your network connection.  There is some info in this article about optimizing network performance: http://www.arcengames.com/forums/index.php/topic,74.0.html

You may also wish to try having the host select a lower MTU setting in the game Settings screen, and/or selecting a lower Network Sync Size.  If none of those work, it's probably best to ask for help in this technical support forum.

If it is a desync:

1. Have every player save a copy of the desynced game.
2. Exit the game and have every player look in their RuntimeData/Save folder, then each upload their copies to a new mantis ticket.
3. Please note which savegame belongs to which named player in the game, and which player(s) were marked with a desync on the host computer.
4. Please let us know if any of the players had been running another campaign prior to the one that desynced in that same run of the AI War program.  That can be a strong clue in some cases.
5. Any added details about what players were doing, and if the issue can be reproduced with certain steps, are always hugely helpful!  Even if you weren't doing anything unusual, anything you can tell us can potentially be a clue as to what actually happened.

Again, this is incredibly rare with AI War, but this is what we will need from you in order to hunt down the issue if it does happen.  Desyncs are the hardest bugs to track down, so we may need some further info and assistance in duplicating if it doesn't turn out to be one of the rarer easy ones.  But hopefully you'll never run into such a bug in the first place -- they are quite rare.  Happy playing!

What to do after a desync:
Assuming that you've already done the savegames and submitted them (or archived them for later submission, if you prefer), then you probably want to keep trying to play.  In order to do this, we strongly suggest that all players in the game close completely out of the AI War program, and then restart.  Don't load any other savegames other than the one you want to play, and then continue on from there.

Sometimes a desync can be caused by some data incorrectly being persisted from one loaded save to the next in the same session of AI War.  If you're able to play without issue after everyone restarts their program, then that's a very strong clue to us that this is what we're dealing with: please let us know either way what you find out on that front, as it can help us immeasurably when figuring out where the desync is.
« Last Edit: January 18, 2011, 11:25:50 PM by x4000 »
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