Docker Container Attached to Network, Network Inspect Shows No Containers - linux

Question

I am simply trying to connect a ROS2 node from my Ubuntu 22.04 VM on my laptop to another ROS2 node on another machine running Ubuntu 18.04. Ideally, I would only have Docker on the second machine (the first machine runs a trivial node that will never change), but I have been trying using a separate container on each.
Here is what I am doing and what I am seeing when I inspect:
(ssh into machine 2 from VM 1.)
A: start up network from machine 2.
sudo docker network create -d overlay --attachable my-attachable-ovrlay
B: start up container 1.
sudo docker run -it --rm test1
C: successfully attach container 1 to the network.
sudo docker network connect dwgyau64pvpenxoj2edu4liqu bold_murdock
D: Confirm the container lists network.
sudo docker inspect -f '{{range $key, $value := .NetworkSettings.Networks}}{{$key}} {{end}}' bold_murdock
prints:
bridge my-attachable-ovrlay
E: Check the network to see container.
sudo docker network inspect my-attachable-ovrlay
prints (among other things):
"Containers": null,
I am new to Docker AND networking, so I could be missing something huge, but I have tried all of the standard suggestions I found online including disabling my firewall, opening a ton of ports using ufw allow on both machines, making sure nodes are active, etc etc etc etc etc.
I tried joining the network from machine 2 and that works and the container is displayed when using network inspect. But when I do that, then machine 1 simply refuses to connect to network.
F: In this situation it gives an error.
sudo docker network connect dwgyau64pvpenxoj2edu4liqu objective_mendel
prints:
Error response from daemon: attaching to network failed, make sure your network options are correct and check manager logs: context deadline exceeded
Also, before trying any docker networking, I have tried plainly pinging from VM1 to machine 2 and that works, both ways. I have tried to use netcat to open an old-timey chat window on port 1234 (random port as per this resource) and that works one way only. I can communicate both ways, but only when machine 1 sends the initial netcat request and machine 2 listens. When machine 2 sends request and 1 listens, nothing happens.
I have been struggling to get this to work for 3 weeks now. I know it’s something stupid, I just know it. Any advice would be incredibly appreciated. Please explain like I know nothing about networking, because I just about do.
EDIT: I converted images (still hyperlinked) into code blocks.

Answer 1

If both PCs are on the same LAN, you could skip the whole network configuration entirely and use ROS2 auto-discovery.
E.g.
PC1:
docker run -it --rm --net=host -v /dev/shm:/dev/shm osrf/ros:foxy-desktop
export ROS_DOMAIN_ID=1
ros2 run demo_nodes_py talker
PC2:
docker run -it --rm --net=host -v /dev/shm:/dev/shm osrf/ros:foxy-desktop
export ROS_DOMAIN_ID=1
ros2 run demo_nodes_py listener
If the PCs are not on the same network, I usually use ZeroTier to create a virtual LAN between PC1, PC2, and PC(N), then repeat the above example.

Answer 2

The issue was that the router was set to 1969. When we updated the time by connecting to the internet for 15 seconds, then disconnected, it started working.