sending udp broadcast from a docker container
You should either run the service defined in your docker-compose.yml file with network_mode: host.
Alternatively you can publish the port of the container you intended to communicate with by publishing it using the following configuration. Note that the /udp is required for UDP communication to work.
service: ports: - "8080:8080/udp"
I have gotten some luck out of this. The guide specifies sysctl parameters that are needed for broadcast forwarding from a docker network, you should then be able to either use his script or specify these parameters when running docker.