Main and backup Engines communicate through the ip addresses and ports set in their configuration XMLs.
However, they receive also messages and commands from the Schedule Publisher Service, which acts like a "bridge" between Radiolive Playout or Executive editor (which allow to control the Engine automation) and Radiolive Engine Service (which actually play the schedule and executes commands).
When the Schedule publisher is started, it detects the ip address of the machine where it's running (it must run along with the Engine service) and that is the ip address it will use to send and receive those commands and messages, performing a bidirectional communication between Engine and Radiolive Playout/Executive Editor.
Example: The operator has to skip an event.
SKIP button is pressed on EE -> the command is sent to the Publisher -> the Publisher sends the command to the Engine -> Radiolive Engine executes the skip operation -> Engine replies to Publisher with the confirmation of the execution -> the Publisher receives the message and forwards it to EE -> EE sets the current event as skipped and shows the next one in play. The schedule is synchronized with the Engine's playlist.
If the workstations have only one adapter and only one IP address, Schedule Publisher service can only use that one and, unless there are network issues, the described communication works properly.
WHAT TO DO IN CASE OF MULTIPLE IP ADDRESSES?
In this case, the Publisher uses the adapter set as default in Windows. You can see which ip address has been chosen from the Configuration tab in Radiolive Playout.
If the workstations can anyway communicate through that ip, everything should work as expected.
Instead, if it's not possible for some reason to send messages through the ip address chosen by Publisher, it's possible to let it take another ip, among the ones assigned to the workstation's adapters.
With Etere version 36.1.332.9426, has been introduced the possibility to force the ip address by the following registry key:
HKEY_LOCAL_MACHINE\SOFTWARE\Etere\IpAddress
The key does not exist by default, it must be created with type STRING and filled with the preferred ip address.
After a restart of Schedule Publisher Service and Radiolive Playout, you will see the correct ip.
In some cases Executive Editor could still have issues.
For example, the backup engine marked in red in the remote panel on EE in the main pc, meaning in this case the module sent a message to the Engine on the wrong ip and it's waiting for a reply that will never come.
Note: You can check on which ip EE is waiting a reply by hovering with the mouse on the red square.
This behaviour means Etere Scheduling ignored the registry key set before, because it has to read it from the following path, instead:
HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\ETERE
So, it's enough to create here the same registry key and set it with the same value. Once Scheduling is restarted, you'll see the issue is fixed.
Additional references
Check the following incidents for more info:
https://su.etere.com/incident/373745
https://su.etere.com/incident/375310
https://su.etere.com/incident/375881