IfTop

Once you use IfTop, you will love it. It is basically top for network usage. Shows the network traffic on any given interface.

Installing is easy:

$ sudo apt install iftop

To check traffic on your LAN connection:

$ sudo iftop -i eth0

To check traffic on your wifi connection:

$ sudo iftop -i wlan0

The following keyboard shortcuts can be used while IfTop is running:

• P: Pause or unpause
• n: Toggle resolving DNS
• t: Toggle between showing traffic of source, destination or both (default)

Tried with: IfTop 1.0 and Ubuntu 14.04