Is there a way to keep an account of which processes generate how much network traffic?

[Yuri]

There is vnstat that does this by interface.

But is there a way to do this by the application? This is because nearly 
every packet that is sent through the system is sent on behalf of some 
process running on the system.

It would be nice to be able to see which applications (in general sense) 
generate most traffic.

I am fully aware that the link between pid and an "application" is vague 
because some processes are run through some cryptic command lines. I am 
just interested if anything exists in this area at all.


Yuri