It's a little unclear what exactly you are asking. Could you clarify exactly what you want to know? There are a number of tools to help monitor and visualize network traffic on a server, but without know exactly what you hope to accomplish it is hard to suggest the best one.

Here are a few utilities you might want to look into in the mean time. Something like bmon will show you simple bandwidth information. While tcptrack can show you information about individual connections. Then there is always tcpdump which streams all the data flowing from you network interface.