How are watchpoints handled? (remote serial)

How should the watchpoints be handled by remote stub/server?
It seems that when 'cont'-command is given, gdb re-installs watchpoint
and sends 'c'-packet.

If the return address is the trap address, the watchpoint trigs again,
but if the address is advanced,
the access is not done at all, because the watchpoint makes exception
before the access is made.