r.q what connect twice? /q tick/r.q [host]:port[:usr:pwd] [host]:port[:usr:pwd]

In the setup instructions for r.q, the comment on the top line of r.q: /q tick/r.q [host]:port[:usr:pwd] [host]:port[:usr:pwd]

Why is [host]:port[:usr:pwd] shown twice? Is it usually the case that this process connect to two things, what are those two things?

Just answered my own question, the RDB needs to subscribe to the TP and the HDB