A publish/subscribe message bus using UDP broadcast packets.
The publish-subscribe channel is a useful design pattern, and there are great tools like Redis Pub/Sub to support it, but sometimes I just want something very lightweight.
The usual ways of designing inter-process communication (IPC) don't allow the fan-out afforded by publish-subscribe channels. Unix domain sockets and unix pipes are both designed to work with a single listener.
UDP broadcast is actually perfect for this. The publisher sends broadcast packets on a known port, and any process on any host of the local network broadcast segment can become a subscriber just by listening for packets on that same port.
The thing that makes this work with multiple processes on the same host is use of SO_REUSEPORT.
(pushd publisher && go build && ./publisher) &
(pushd subscriber && go build && ./subscriber)Broadcasting to 255.255.255.255 really does send to every machine on the local broadcast segment of the network. This behaviour may be desirable (or not) depending on your needs and your network architecture.