By default, can a docker container call host's localhost UDP?
Opening ports is only needed when you want to Listen for the requests not sending. By default Docker provides the necessary network namespace for your container to communicate to the host or outside world.
So, you could it in two ways:
use
--net hostin yourdocker runand send requests tolocalhost:8125in this case you containerized app is effectively sharing the host's network stack. So localhost points to the daemon that's already running in your host.talk to the container network gateway (which is usually
172.17.0.1) or your host's hostname from your container. Then your are able to send packets to your daemon in your host.