A simple way to monitor network traffic (not internet traffic)?

Hi,

I am looking for a simple way to monitor traffic on my network. I've setup my Raspberry Pi to share media to multiple devices and sometimes I get really slow transfer speeds when copying files over the network. So, I am looking for something that tells me how much data and what speed each device is pulling from the Pi. For example, "iPad has downloaded 42GB at 15MB/s".

I did some searching and it looks like Wireshark might be what I am looking for but it looks complicated. Maybe someone can instruct me on how to get the information I want from Wireshark? Thanks.