> When I parameter httrack, for example,  I put 2 sockets, 
and 
> maxrate=10000.
> Does it mean that each socket has a max rate of 10000, or 
the max rate 
> is global for the 2 sockets (ie 5000/sockets) ?
The maximum global rate is 10000 for all sockets ; but you 
can have one with 8000B/s and the another one at 2000B/s.

> Do you know what is the difference between the number 
of 'socket' and 
> the 'number of connection'? 

These are the same.