Known causes of desyncs in Extended online games

This page lists known causes of desyncs and ways to work around them.

A 'desync' is when a player loses connection to an online game because the player's copy of the game and the server's copy have somehow got different data (they have 'desynchronized'). For an online game to run correctly, the server and every player must have exactly the same data about everything on the map: what is built on every tile, the speed of every convoy, the state of every signal, etc. A desync doesn't mean the player has done anything 'wrong'. Sometimes it is caused by the player forgetting to update something; more often it means that there is a bug in the game . However, desync bugs are very difficult to understand and fix, because there are millions of different data items in a large multiplayer map and are many possible reasons that could cause a convoy to be travelling slightly slower or faster. All the Simutrans developers are volunteers doing this for fun in their spare time, so it can take a long time (years) to fix such bugs.

1. pak128.Britain-Ex Demo game

When you first start a new installation of Simutrans-Extended, the game uses the pak128.Britain-Ex graphics and begins with its Demo game running. It's a really beautiful model of mid-20th century British transport. Unfortunately, if you try to connect to an online game after the Demo game, you will always immediately desync.

There are several ways to work around this bug.

1a. Load another map before connecting online

After you start the game, load any map except the demo game and then connect to the online game using the in-game Network Window:



If you don't have one, make one. Smaller maps with fewer cities and industries work better for this purpose since they will be made and load more quickly.

1b. Command line using the -load parameter

If you are comfortable with starting the game from the Linux or Windows command line, you can join online games directly without loading the Demo game by using the -load net: parameter and the server's domain name or IP number. For example, to directly join the Bridgewater-Brunel server on Linux, use:
./simutrans-extended -load net:bridgewater-brunel.me.uk
Note that that there is no space after net.

The next time you want to do this, you may be able to get the command back using the UP ARROW key on the command line.

If this doesn't work, please see ''Can't connect?' below.

1c. Create a shortcut on your desktop

In most operating systems, you can create a shortcut so that you don't need to type on the command line every time. The procedure for this will vary depending on your GUI.

1c (i). Windows

To be added.

1c (ii). Gnome

Unfortunately, Gnome has removed the ability to automatically create desktop shortcuts in recent versions. You can follow this guide to create one using a text editor and the command line, but it may be quicker to just use the terminal.

1c (iii). KDE

1. Right-click on the desktop, choose Create New...
2. Choose Link to Application:


3. Click on the Applications tab
4. Click on Choose, go to the place where you installed Simutrans-Extended, and choose the simutrans-extended file
5. It's address should appear in this box
6. Change Link to Application to the name of the server where you want to play (or something else convenient)


7. Add -load net:bridgewater-brunel.me.uk (or the name of the server you want) in the Command box
8. Click OK


You can now directly connect to the server from this shortcut. If it doesn't work, check Can't connect? further down this page.

Can't connect?

Some of the ways of starting a game listed on this page bypass the normal check that the server and player are using the same version of the game and pakset. So it is your responsibility to make sure that you are using the Nightly Updater or another method to keep your game version up to date with the server (see incompatible versions). The game version of public servers is displayed on the Extended server list.