You have a typo in connect method: IHM_connetion
QObject::connect(&server,SIGNAL(**IHM_connetion**())
while the emitted signal is:
emit IHM_connection()
QObject:connect returns a bool value which indicates if signal-slot connection was successful. Checking this value (for example, with Q_ASSERT) is a good practice and can save you a lot of time in case of typos like this. .