NATS Subject Profiler
Connect it to the demo NATS server.
nats-subject-profiler -server demo.nats.io:4222
You may see some subjects come through. However, if not, you can publish to the server in another shell using the NATS CLI
nats --server demo.nats.io pub foo 'hello'
Note, that subject deduplication is on by default, so if you publish multiple times you will only see the profile print it out once.