Chaining simulations

Chaining simulations allows two simulations where borders exist between them to interact.

This is a tutorial on how to set up a chain, it assumes you have sorted out any IP address and port issues there may be.

You may chain any number of sims that are designed to connect with each other. Please refer to the appropriate sim pages and the chaining diagram for that information.

You may chain over the Internet with any other player, within one computer to enable solo play, or even a combination of both.

For chaining within a single computer the IP address will always be 127.0.0.1 but the principle of how to chain remains the same.

Before you begin, you should select a series of sims that are able to be chained. The chaining diagram is helpful to assist with your selection. Each sim should use a compatible timetable that has been designed to be chained. At each connecting point between sims, one should be designated the master sim and the other the slave.

Setting up the sims

Step 1	Begin a New Simulation with the master sim, or load an existing save. Configure as appropriate. It is helpful select 'Start simulation paused' when chaining.
Step 2	On the networking details screen, enable the SimSig Server. Enter up to 4 initials in the box provided, this will identify you when sending messages to the chained sims.
Step 3	Make a note of the IP address and port selected as the slave sims will require it.
Step 4	Click Start.

Master Sim

When a slave sim connects, you will be prompted to accept the connection request.

Slave Sims

Step 1	Follow Steps 1-5 for setting up sims. If on the same machine as the master, make sure you use a different port to the master simulation. If you are hosting for other players on the internet, you'll have to set up port forwarding for this port as well.
Step 2	Once the sim has loaded, in the control window , select 'Multiplayer > Connect to External Signalbox'. Select the master sim from the list and ensure 'Synchronise time' is ticked.
Step 3	Enter the IP address and port of the master sim you are chaining to. If you are running the master simulation on the same computer, use the local IP address which is 127.0.0.1.
Step 4	Steps 2-3 may be repeated to chain to other sims, however only one of the chaining connections may have 'Synchronise time' selected. See below for further details.

Timetables

It is important that all simulations in the chain are using timetables that are compatible with each other. If this is not the case, trains crossing the simulation boundary may have no schedule on the other side.

Simulations should be chained at the timetable start time, or using a saved game made when the simulations were chained. This ensures that the two simulations are in sync and both simulations will get all the trains they should do.

Chaining more than two sims

This can be a linear chain or a more complex arrangement.

It does not matter which sim you chose as the 'master ' as long as the chain is completed across all the interfaces. This will mean entering an IP address in more than one chaining box. The more crucial point is to ensure the synchronisation is complete as you can only synchronise with one adjacent box whereas you chain with more than one. If the simulations are being run on the same computer, each simulation must be assigned its own port.

For example: North London Line , King's Cross , Peterborough and Cambridge .

Set Cambridge as the 'master ' and then chain

King's Cross to it followed by Peterborough chained to both and then North London Line chained to King's Cross.
As far as synchronising is concerned you can synchronise North London to King's Cross and King's Cross to Cambridge and Peterborough to Cambridge, or you can synchronise King's Cross to Peterborough or vice versa: as long as there is a logical sequence to synchronising leading back to the single 'master' sim it should work.
Note: in this case King's Cross acts as a 'master' to Peterborough and North London as well as being the 'slave' to Cambridge.

In all cases, simulations must be explicitly chained to each other- you cannot, for example, chain Peterborough to Cambridge and Cambridge to King's Cross and expect trains to cross the KX/Peterborough boundary between Hitchin and Biggleswade- King's Cross and Peterborough must also be chained together.

Notes

Wrong direction moves over lines between chained simulations are generally not supported.
Once a chain has been started, it is unadvisable to remove a sim from the chain. The severing of chains is likely to lead to instabilities.

Last edited by y10g9 on 30/05/2021 at 20:01