Communication between swarms

Hello,

I have two main question, one related to Traefik and Swarm and another one related to elk and Swarm.

So I would like to know if it’s possible for example to use swarm to publish two web apps with Traefik. So far I can publish my apps and Traefik on the same swarm. I was wondering if it would be possible to publish traefik in a separated swarm as well for the two apps.
Why do I want to do this ? I want to separate my two apps so they don’t live in the same swarm and use the same Traefik “swarm” for both app. Because since I have only one server, if I use another Traefik container I will not be able to map to the 80 port. (except if there is something I misunderstood)
But as far as I know it’s apparently not possible for swarm to communicate with each other.

I also have the same question related to elk. I have elk which is dockerized, and now if possible I would like to monitor all my swarms. I read some tutorial where elk lives outside of any swarm. Now my question is if I use swarm for the elk stack would I be able to monitor the others swarm ? Because if understood correctly it’s not possible for swarms to communicate with each other. So it’s the same problem as my first question.

Thank you in advance for your help