msoak is a utility to simultaneously subscribe to an arbitrary
number of topics on any number of MQTT brokers and optionally
modify or normalize received payloads before printing them out.
This utility was created for being able to back up to a central
location messages received by a number of brokers; instead of
launching (and having to monitor success of) a large number of
mosquitto_sub(1) programs, msoak took on the job.

msoak uses asynchronous connects to the MQTT brokers so that it
can handle situations in which a broker may temporarily be
unavailable.