Bon bein apres quelques recherche...
Pour ceux qui se posent la même question qe moi 
(Pas eu le temps de traduire)
StarCraft is not designed for several PCs sharing the same internet connection.
There is a non-supported way, though, which may work out for you. It will require
you to modify the Windows Registry. If you are not familiar with editing the registry,
ask someone for help.
On one computer of your choice click Start, Run..., type "regedit" and press Enter.
Go to HKEY_CURRENT_USER\Software\Battle.net and click on "Configuration". On the right
half of the window do a right-click and create a new DWORD value. Call it "Game Data Port".
Then right-click on the newly created value and select "Modify".
In the new window, click on Decimal (not Hexadecimal) and enter 6113 as value.
Apply the settings, then close the registry again.
This computer will now use port 6113 on Battle.net (applies to StarCraft and maybe to Diablo II
as well, but definitely not to Warcraft III).
Repeat the procedure for any additional computers that may be behind the router, but use a different
port value then (6114, 6115, 6116, ...). Keep in mind that each computer will have to have a different
port value assigned.
The default port value is 6112, so one computer will use this port by default, which is perfectly fine
(since you will not need to modify anything here! 
).
In addition, please make sure that ports 6112 up to 6119 TCP/UDP are forwarded ("opened" )
on your router.
Your router's manual and/or the the manufacturer's website surely offer help on how to forward
("open" ) ports.
