Welcome to Rolling Line multiplayer!
(well not yet, it's not released, but will be within the coming months)

I am making this guide ahead of time to help with beta testing, and it will be updated as time goes on before multiplayers official release.


Firstly, I'll explain the basics of what Rolling Line can actually do in terms of multiplayer.
Anyone can "host" a game and invite their friends (or anyone with the join code) to join their game. This is all done in-game and doesn't require any special software.

Rolling Line is peer-to-peer, which means there are no dedicated servers and it is up to players to host their own servers.
This also means there is no public server browser, so people can only join your server if you invite them directly (through Steam) or share with them your servers join code.

Multiplayer servers can either be hosted using Steam (which requires an online Steam account for everyone joining the server) or you can also host a server directly, using your own IP address, which does not require a Steam account.

When playing multiplayer you can drive trains, spawn/remove trains, interact with the world (like opening doors, using electronic circuitry, etc), load/unload freight, move turntables, etc.
But you can not edit the map or place/remove props and track.
This is currently the main limitation of multiplayer, but in the future this may change if I manage to make multiplayer support for map editing in a future update.

Multiplayer fully supports all mods, meaning modded trains, liveries, track and props.
Players joining the server do need to have these mods downloaded themselves to see them though (this will be explained in the mods section of this guide)

If you want to play a multiplayer game with your friends one of you will need to host a server.
This is actually really simple and only takes a couple of button presses thanks to Steam's networking features!

Firstly, go to the "Pause menu -> Multiplayer" menu and choose the "Host a server" option:



Next, simply click "Start server" and you're ready to go!



From this screen you will have a few options for inviting players to your game.
Firstly, the easiest way is to click the "Invite steam friends" button in the bottom corner. You can then click on any online player in your friends list and they will be sent an invite to directly join your game.



The second way to invite people is to copy the "join code" that you can see in the middle of the screen. This join code is always a long number, like this:

76561198843894471

You can click the copy icon below the number to copy it to the clipboard.

Once you have your join code, you can send this to your friends to let them join your game. You can also share this code publicly if you want other people to be able to join your game.


You will also notice a toggle option in the bottom right corner for "allow direct joining".
If you enable this option then anyone on your Steam friends list will be able to join your game directly by clicking on your profile and choosing the "Join game" option:





When players join your server they will need to load the same map as you.
If they have a copy of the same map download (like by subscribing to the same map on the Steam Workshop as you) then they will load this copy.
If they don't have a copy of the map they will instead have the map file automatically transferred to them over the network while joining the server. This is not recommended though, as it can be very slow to transfer large maps and any packaged mods will not be included.

If you are wanting to play a large map together, it is highly recommended that all of the players download a copy of the map from the Steam Workshop before joining the server!

There is more info about sharing maps and mods over the Steam workshop in the "Using mods" section of this guide.

Once one of your friends is hosting a game, joining their game is very simple. There are a couple of different ways to do this:

• Receiving a Steam invite
  The person hosting the server can send you a direct invite on Steam, which you will receive as a Steam message notification. Simply click on "Play game" and Rolling Line will launch and automatically join you directly to the server.
  
  
  
  
• Using a join code
  Instead of a direct invite, the server host can also send you a "join code" which is a long number key that looks like this:
  76561198843894471
  
  To join a server with this code, first open the "pause menu -> multiplayer" menu (or the "Multiplayer" menu option on the main menu when starting the game) and then click "join a server":
  
  
  
  Next you will be shown a text box for entering the join code. Simply copy-paste the join code you were sent by the server host and click "Join server":
  
  

When joining a server you might also be asked for a password if the host has a password enabled.
If so, they will need to tell you the password, then you can enter it in-game and continue.

If the server host has banned your account then you will instead be booted back out of multiplayer and shown a message saying "You are banned from this server".

Mods are fully supported in multiplayer.
When a mod is being used in a multiplayer session you will be able to see it and interact with it as long as you have a mod downloaded yourself.

In the case of train mods, if a player on the server does not have the mod downloaded then they will see a placeholder model instead (but they can still drive it).



It is not recommended to spawn mods that the server host does not have downloaded though as there will be some inconsistencies (like coupling distance and special effects like custom lights) which will not behave has expected if the server host does not have information about the mod you've spawned.

Prop mods and track mods will work just like in singleplayer, where they will only be visible if you have the mod downloaded, otherwise they will be missing from the map.

When playing on a map that uses mods it is highly recommended to make a "collection" on Steam to organize all of the required mods together, and then make sure everyone playing on your server has the collection downloaded.



Packaged mods also work just like in singleplayer. For example, if your server is hosting a game on a large workshop map like the Gorre & Daphetid Railroad...
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=3369355289&searchtext=
As long as everyone joining your server has this workshop item downloaded then all packaged mods inside the map will load correctly.


If you don't want to share mods publically on the Steam Workshop but want to use them in multiplayer, you can instead share the mod files directly with the people joining your server.
This can be done by copying the mod folders (if you created these yourself they will be found in the "...Steam...\Rolling Line\Modding\Mods" folder).



Copy these folders and send them to the other players who are joining your server. Then they should paste these folders into their own "mods" folder.
This is essentially just an offline way of sharing mods and works in exactly the same way as having them downloaded from the Steam Workshop.

Before creating a server you can edit some settings to control how the server runs. You can access these options by opening the "Pause menu -> Multiplayer -> Create a server -> Hosting options" menu before starting a server:



From this menu you can edit several things. These are:

• Manage bans - Opens a list of all the players that you have banned from your server. From this list you can click the "x" icon next to their name to remove them from the ban list.
  
• Allow save file share - If this option is enabled players will remain in your save file after they disconnect from your server, and can freely edit and save a copy of the map. Otherwise if this option is disabled, they will be returned to their last save file when they disconnect. Basically you should keep this option disabled if you don't want joining players to be able to make a copy of your map.
  
• Use password - Enable this option if you want players joining your server to require a password. They will be asked to enter this password before joining.

If you want to host a game on your "Local area network" (LAN) then you can easily do this using the "Direct IP" server hosting option.
Player over LAN means everyone in the server is using the same local network, like if everyone is in the same house using the same WiFi or Ethernet cables.

Here are the steps for setting up a LAN game:

• Firstly, the host should start a server as normal by going to the "Pause menu -> Multiplayer -> Host a server" menu. But instead of using "Steam" as the connection method, change this to "Direct IP"
  
  
  
  
• To host a server you will need two things, an IP address and Port number.
  Luckily for a LAN game this is quite simple. Click the button "Use LAN ip" and the game will automatically set your IP Address to use your local address. You can keep the port the same (7777 is the default).
  
  For example, my local IP address will be "192.168.1.100" (this will always begin with 192.168, and the second numbers will be different depending on how many devices are connected to your local network).
  
  If you want, you can also enable the "Broadcast over LAN" option. This will make other players on your local network find your server details automatically. But this is unreliable and does not always work on all kinds of networks. Regardless, this step is not required so you can ignore it if you want.
  
  Next click "Start server" to continue, and you will see this screen:
  
  
  
  
• The next step is for other players on your local network to join your server using these details (the IP Address and Port).
  
  Each player should open the server join menu "Pause menu -> Multiplayer -> Join a server" and also change the "connection type" to "Direct IP":
  
  
  
  From here you can enter the details for the host's server.
  If the host enabled the "Broadcast over LAN" option then you can click the "Search" button and the server details should fill out automatically (but this does not always work and is unreliable).
  
  Or you can enter the server details manually using the text boxes.
  Make sure the IP Address and Port are the same as the host, and click "Join server".
  
  And that's all you need to do to connect with players over a LAN game!

If you don't want to use the Steam networking system (e.g. if you want to play over LAN, or host a server yourself without relying on Steam's servers) then you can instead host a server using your own IP Address without a connection to Steam.

The previous section of this guide explains how to do this for making a LAN server, but with some more advanced steps you can also create a public server over the internet.

As mentioned in the previous section of this guide, you will need to open the "Pause menu -> Multiplayer -> Create a server" menu, then change the connection type to "Direct IP".

The next part of this is much more complicated.
You will need to do something called "Port forwarding", which involves changing advanced settings on your router (or using special software) to open up a specific port on your router for public access.

There are lots of different guides for this online, and the process is very different depending on the kind of modem you have. I recommend searching for something like "How to enable port forwarding for an X brand router" (which your own brand of router of course).

Once you have port forwarding set up with your router you can then use that port as a public connection over the internet to host a multiplayer server.


You can figure out your own public IP address by searching "what is my IP" on your search engine of choice, and you should see a note like this:



Now if you return to your server setup back in Rolling Line, you can set your server hosting IP Address to the public IP Address you found.
Then set the Port to the same port that you enabled port forwarding for.

Next, start a server as normal, and have people join using the same IP Address and Port that you used to set up the server!