[Iftop-users] by port

[x123@onperfect.com]

Ok, I'm going to apologize ahead of time for being thick headed.
I'm just missing it I guess. We've been using iftop for months.
In the past couple of months iftop is in continuous use. We have
a wireless network 50 nodes, 11 Mbps funneling into a T-1.
We have some abusers of course. Otherwise it would run fine. 

I was looking at the iftop home page and saw there is a way to
turn on source port, but can't figure out how. The below line
appears, but I don't know how to get that to happen either.
Thank You in advance for your patience and your help. 

For starters how to we get that exact screen? 

Host names hidden, source port shown, one line per host pair = network 
traffic by service