numPubSub (int): number of publisher and subscriber pairs
rate (float): number of messages per second approximately by exponential randomness

node mqtt-bm.js --host="127.0.0.1"  --numPubSub=10 --rate=1

optional parameters:
limitLogging (boolean): limits number of messages sent logging to every 5 seconds for long duration logging
timeout (int): number of seconds before the program will automatically end and report (off by default, will run infinitely until cancelled)

node mqtt-bm.js --host="127.0.0.1"  --numPubSub=10 --rate=1 --timeout=60 --limitLogging=1