Docker Swarm join-token not working
The swarm protocol is not http, so you will not be able to pass it through a proxy. Swarm nodes need direct communication between each node on port 2377/tcp (or your configured swarm port), 7946/both, and 4789/udp. If you configure an overlay network with the secure option for IPSec, then you'll also need protocol 50 open between the nodes.