Fortinet Firewall: Packet Capture By Port Number In CLI

I like packet captures.  I have probably said that a million times, because it "proves" what is going on, on a network, instead of guessing what is going on.  Packet captures are a Net Admins best friend, plain and simple. 
So here is how you do a packet capture when you are looking for traffic using a specific port number in particular in CLI of a Fortinet:
diagnose  sniffer packet any 'tcp port 8883' 4 0 a

Above, Im looking for traffic on TCP port 8883.  Ill see everything that passes through the firewall.