Network control

Hello all,

I would like to know if anyone knows any application that would look at my network and tell me who is connected and what traffic is coming and going out.
The network is a small environment with a wireless router and 5 users, no server. But I would like to be able to get those information from my laptop.
The router can let me know who is connect but unfortunatly does not show me the traffic.

Hope someone can help me
Rui