Well, changing LOCAL_SOCKET_ID from -500000 to 15000 make 
httrack working...

I don't know yet if it could lead to others problems. (if a 
socket with this Id already exists for example ...)

I made a little prog based on the example of the manpage to 
check out why FD_SET crashed.
With fd<0 :crash
fd > 15103 crash (why 15103?)

Is my version of FD_SET too old? do I need to update 
something?anyway I will continue with LOCAL_SOCKET_ID changed as long 
as it works ...

GuiOm